JP7595447B2 - Display device, display method, and program - Google Patents

Description

The present invention relates to a display device that sets the brightness of an output image depending on whether or not there is a scene change in an input image.

For example, Patent Document 1 discloses a technology for setting the luminance of an output image in a display device depending on whether or not there is a scene change in an input image. In the image processing device disclosed in Patent Document 1, a gamma curve is generated as follows. When there is no scene change, a first calculation is performed based on the previous frame to generate a gamma curve for the next frame and subsequent frames. On the other hand, when there is a scene change, a second calculation is performed based on the statistics of the frame where the scene change has occurred, and the gamma curve is generated in a shorter time than the first calculation. In addition, the second calculation estimates the gamma curve obtained by the first calculation. In other words, the second calculation generates a gamma curve close to the gamma curve obtained by the first calculation. Therefore, it is possible to reduce the transition in brightness that occurs when a time direction variation suppression process is performed in which the gamma curve is changed gradually with a certain time constant.

JP 2014-11725 A

However, when changing from a bright scene to a dark scene, if the gamma curve is gradually changed from the previous scene, the black areas of the dark scene will gradually become blacker from the brightness of the previous scene, resulting in a visual phenomenon known as white floating, where the area appears to go from slightly white to dark.

One aspect of the present invention aims to realize a display device that can suppress white floating in low gradation areas while suppressing screen flickering in the output image after a scene change when a scene change occurs.

In order to solve the above problem, a display device according to one aspect of the present invention includes a scene change detection unit that detects whether or not a scene has changed on a frame-by-frame basis in an input image composed of a plurality of frames, a brightness value setting unit that sets a brightness value of a first image for a frame detected by the scene change detection unit as having a scene change, and a display control unit that displays an image on a display unit based on the brightness value of the first image, and the brightness value setting unit includes a region determination unit that determines whether a predetermined region of the first image is a first region having a gradation lower than a preset gradation or a second region other than the first region, a first brightness value setting unit that sets the brightness value of the first region determined by the region determination unit to a brightness value within a first range of low gradations that includes the luminance value of the first region of the first image, and a second brightness value setting unit that sets the brightness value of the second region determined by the region determination unit to a brightness value within a second range that includes the luminance value of the second region of the first image and has a lower limit value that is higher than the upper limit value of the first range.

A display method according to one aspect of the present invention is a display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance set according to a scene change of the input image, and is characterized by including a scene change detection step for detecting the presence or absence of a scene change on a frame-by-frame basis of the input image, an area determination step for determining whether a predetermined area of a first image for a frame detected as having a scene change by the scene change step is a first area having a gradation lower than a preset gradation or a second area other than the first area, a first luminance value setting step for setting the luminance value of the first area determined by the area determination step to a luminance value within a first range of low gradations including the luminance value of the first area of the first image, and a second luminance value setting step for setting the luminance value of the second area determined by the area determination step to a luminance value within a second range including the luminance value of the second area of the first image and having a lower limit value of a luminance value higher than the upper limit value of the first range.

According to one aspect of the present invention, when a scene change occurs, it is possible to suppress screen flickering and whitening in low gradation areas in the output image after the scene change.

1 is a schematic configuration block diagram of a display device according to a first embodiment of the present invention. FIG. 2 is a front view showing the appearance of the display device shown in FIG. 4 is a flowchart showing the flow of a gamma curve generation process in the display device shown in FIG. 1 . FIG. 11 is a diagram for explaining scene change detection. FIG. 11 is a diagram for explaining image comparison processing. This is the gamma curve for the frame before the scene change. This is the gamma curve for the frame after the scene change. FIG. 11 is a diagram for explaining the number of reference frames when setting luminance. FIG. 11 is a diagram for explaining another process of image comparison. FIG. 13 is a diagram for explaining still another image comparison process. FIG. 11 is a schematic block diagram of a display device according to a second embodiment of the present invention. 12 is a flowchart showing the flow of the display device gamma curve generation process shown in FIG. 11 . FIG. 11 is a schematic block diagram of a display device according to a third embodiment of the present invention. 14 is a flowchart showing the flow of the display device gamma curve generation process shown in FIG. 13.

The following describes an embodiment of the present invention in detail. However, unless otherwise specified, the configuration described in this embodiment is merely an explanatory example and is not intended to limit the scope of the invention.

[Embodiment 1]
Hereinafter, one embodiment of the present invention will be described in detail.

(Overview of the display device)
A display device 1 according to the present embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a block diagram showing the configuration of the display device 1 according to the present embodiment. Fig. 2 is a perspective view showing the external appearance of the display device 1.

As shown in FIG. 1, the display device 1 includes an image acquisition unit 11, a scene change detection unit 12, a brightness value setting unit 13, a gamma curve generation unit 14, a panel control unit 15, and a display panel 16.

The image acquisition unit 11 acquires an input image made up of multiple frames. The image acquired by the image acquisition unit 11 is, for example, a video signal such as an HDR signal. The HDR signal can be an HDMI (registered trademark) signal based on the HDMI (registered trademark) (High-Definition Multimedia Interface) standard, a Tuner signal (a signal received by a tuner), a CVBS (Composite Video, Blanking, and Sync) signal, and the like.

The image acquisition unit 11 has a memory unit 111 that temporarily stores the acquired input image for each frame, and an analysis unit 112 that analyzes the acquired input image for each frame. At least a part of the analysis information analyzed by the analysis unit 112 is sent to the downstream scene change detection unit 12. The analysis information includes at least the minimum luminance value, the maximum luminance value, APL (Average Picture Level), and a histogram. Meanwhile, the input image acquired by the image acquisition unit 11 and temporarily stored in the memory unit 111 is sent to the downstream gamma curve generation unit 14 as information indicating the input luminance before correction for each frame.

The scene change detection unit 12 detects whether or not there is a scene change in the input image based on at least a portion of the analysis information for each frame sent from the image acquisition unit 11. A signal indicating the detection result by the scene change detection unit 12 is sent to the subsequent brightness value setting unit 13.

The luminance value setting unit 13 sets a luminance value in the output image of the frame that is the target of scene change detection, according to a signal indicating the detection result sent from the scene change detection unit 12. The luminance value setting unit 13 generates a correction signal for correcting the gamma curve from the set luminance value, and sends the generated correction signal to the downstream gamma curve generation unit 14. Details of the luminance value setting unit 13 will be described later.

The gamma curve generation unit 14 corrects the input luminance for each frame stored in the memory unit 111, sent from the image acquisition unit 11, based on the correction signal sent from the luminance value setting unit 13, and generates a gamma curve for each frame from the corrected input luminance. Information indicating the gamma curve generated by the gamma curve generation unit 14 is sent to the panel control unit 15 in the subsequent stage.

The panel control unit 15 sets the output luminance of each pixel of the display panel 16 based on the information indicating the gamma curve generated by the gamma curve generation unit 14. This allows the image represented by the video signal to be displayed on the display panel 16 at its original luminance.

The frame rate of the display panel 16 is 240 FPS (updated 240 times per second).

(Brightness value setting unit 13)
The luminance value setting unit 13 includes an image comparison unit 131, an area determination unit 132, a first luminance value setting unit 133, a second luminance value setting unit 134, a third luminance value setting unit 135, and a correction signal generation unit 136. In the luminance value setting unit 13, the first luminance value setting unit 133 and the second luminance value setting unit 134 set the luminance value of an output image (first image) for a frame detected as having a scene change. The third luminance value setting unit 135 sets the luminance value of an output image (second image) for a frame detected as having no scene change. The correction signal generation unit 136 generates a correction signal for correcting the gamma curve from the luminance value set by the first luminance value setting unit 133 and the second luminance value setting unit 134 or the third luminance value setting unit 135.

When the signal indicating the detection result from the scene change detection unit 12 indicates that a scene change has occurred, the image comparison unit 131 compares the images before and after the scene change. Specifically, the image comparison unit 131 determines whether the image after the scene change is darker than the image before the scene change. The image comparison unit 131 then sends the result of the image comparison to the downstream area determination unit 132 and third brightness value setting unit 135. Details of the image comparison by the image comparison unit 131 will be described later.

The area determination unit 132 performs area determination when the signal indicating the image comparison result from the image comparison unit 131 is a signal indicating that the image after the scene change is darker than the image before the scene change. That is, for each predetermined area of the first image corresponding to the frame that was the subject of scene change detection, i.e., the frame detected as having a scene change, it determines whether the area is a first area with a gradation lower than a preset gradation, or a second area other than the first area. Here, the "predetermined area" may be set according to the type of image after the scene change (such as a night view or an image of scenery including the sea) or may be set to a preset size. The "predetermined area" may be the entire area of the image, or a part of it. This "area" may be one pixel or a collection of multiple pixels.

In addition, when taking into consideration the accuracy of the area determination, it is preferable to perform the area determination for each pixel in the entire area of the first image.

The first luminance value setting unit 133 sets the luminance value of the first region determined by the region determination unit 132 to a luminance value within a range from the luminance value of the first region in the output image of the frame that is the subject of region determination to a first threshold value. That is, when a signal indicating the detection result from the scene change detection unit 12 is a signal indicating that there is a scene change, the first luminance value setting unit 133 sets the luminance value of the first region of a lower gradation than a preset gradation in the output image (first image) for the frame that is detected as having a scene change to a luminance value within a first range of lower gradations that includes the luminance value of the first region of the output image.

The first range here refers to a range of brightness values between 0 and 3, where brightness values are expressed in 256 levels from 0 to 255, with level 0 being black. Note that the first range is not limited to a range of brightness values between 0 and 3, and the upper limit of the brightness value may be greater than 3. Also, the brightness value of the first region may be set to the same brightness value as that first region of the first image.

The second luminance value setting unit 134 sets the luminance value of the second region determined by the region determination unit 132 to a luminance value within a range from the luminance value of the second region in the output image of the frame for which the region is to be determined to a second threshold value that is greater than the first threshold value. In other words, the second luminance value setting unit 134 sets the luminance value of the second region other than the first region in the output image (first image) for the frame detected as having a scene change to a luminance value within a second range that includes the luminance value of the second region of the first image and has a lower limit value that is greater than the upper limit value of the first range.

The second range is a range of luminance values between 4 and 255, which is greater than the upper limit luminance value defined in the first range (3 luminance levels in the above example), when luminance values are expressed in 256 levels from 0 to 255, with 255 being white. If the upper limit luminance value of the first range changes, the lower limit luminance value of the second range also changes. The second range may also be set based on first image information corresponding to the first image and second image information corresponding to the second image for a frame earlier than the frame for the first image.

The third luminance value setting unit 135 sets a luminance value in the output image (third image) for the frame when the signal indicating the detection result from the scene change detection unit 12 is a signal indicating no scene change. Also, the third luminance value setting unit 135 sets a luminance value in the output image (fourth image) for the frame when the signal indicating the image comparison result from the image comparison unit 131 is a signal indicating that the image after the scene change is not darker than the image before the scene change. That is, the third luminance value setting unit 135 sets the luminance values of the third image for a frame without a scene change and the fourth image with a scene change that is not darker than the image before the scene change.

The third luminance value setting unit 135 includes a reference frame number setting unit 1351 and an average value calculation unit 1352. That is, the reference frame number setting unit 1351 sets the number of reference frames used to correct the input luminance according to a signal indicating the presence or absence of a scene change sent from the scene change detection unit 12. Here, the reference frames include a current frame to be detected for the presence or absence of a scene change and past frames consisting of several frames going back consecutively from the current frame. The reference frame number setting unit 1351 sets the number of reference frames when there is a scene change to be less than the number of reference frames when there is no scene change. Specifically, the reference frame number setting unit 1351 sets the number of past frames constituting the reference frame to be less when there is a scene change than when there is no scene change. The signal indicating the number of reference frames set by the reference frame number setting unit 1351 is sent to the subsequent average value calculation unit 1352.

The average value calculation unit 1352 sums up the APLs from the analysis information of each frame that constitutes the reference frame based on a signal indicating the number of reference frames sent from the reference frame number setting unit 1351, and then divides the summed APL by the number of reference frames to obtain the average APL. The average APL value obtained by the average value calculation unit 1352 is sent to the correction signal generation unit 136 at the subsequent stage.

The correction signal generation unit 136 generates a correction signal for correcting the gamma curve from the luminance values set in the first luminance value setting unit 133 and the second luminance value setting unit 134, or the third luminance value setting unit 135, and sends the generated correction signal to the downstream gamma curve generation unit 14.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 1 having the above configuration will be described with reference to Figs. 3 to 8. Fig. 3 is a flowchart showing the flow of the gamma curve generation process. Fig. 4 is a diagram for explaining scene change detection. Fig. 5 is a diagram for comparing the darkness of the output image before and after a scene change. Fig. 6 is a diagram showing a gamma curve of the output image of the frame before the scene change. Fig. 7 is a diagram showing a gamma curve of the output image of the frame after the scene change. Fig. 8 is a diagram for explaining the number of reference frames when setting the output luminance.

First, the scene change detection unit 12 judges whether or not there is a scene change (step S11). That is, the scene change detection unit 12 detects whether or not the input image of the current frame is an image in which the scene has changed from the input image of the previous frame, that is, whether or not there is a scene change. Specifically, the scene change detection unit 12 detects whether or not there is a scene change from the histogram of the analysis information sent from the image acquisition unit 11. For example, in four consecutive frames A, B, C, and D shown in FIG. 4, the histograms of the previous and following frames are compared for each BIN (one bit of binary data) to obtain the difference in frequency for each BIN. If the sum of the absolute values of the obtained differences is equal to or greater than a preset value, it is determined that there is a scene change in the latter frame of the two compared frames. Here, in the example shown in FIG. 4, when the set value of the judgment criterion is 3515, the scene change detection unit 12 detects that there is a scene change between frame B and frame C, where the sum of the absolute values of the difference in frequency is 4000. Furthermore, when the sum of the differences in the absolute values of the frequency differences is 0 or 3000, both are smaller than 3515, so the scene change detection unit 12 detects that there was no scene change between frames A and B, and between frames C and D. Note that the frame size assumed in FIG. 4 is 3840 x 2160 if the display device 1 is a 4K TV, and 7860 x 4320 if the display device 1 is an 8K TV.

Next, if the brightness value setting unit 13 detects that there is a scene change in step S11 (YES), it proceeds to step S12. In step S12, it is determined whether the first image corresponding to the frame in which the scene change is detected by the image comparison unit 131 is darker than the second image corresponding to the frame immediately before the frame in which the scene change is detected. Here, the image comparison unit 131 uses the brightness histogram of the image to determine whether the first image is darker than the second image. For example, the image of scene A shown by reference numeral 1051 in FIG. 5 is the second image before the scene change, and the image of scene B shown by reference numeral 1052 is the first image after the scene change. At this time, the image comparison unit 131 compares the darkness of the first image and the second image from the brightness histogram of the second image shown by reference numeral 1053 and the brightness histogram of the first image shown by reference numeral 1054. Here, the brightness is set to 256 gradations, and a threshold value B of the brightness value (gradation) is set in each brightness histogram. The threshold value B is set to, for example, 30 gradations. Therefore, the image comparison unit 131 determines that the first image is darker than the second image when the proportion of pixels with luminance values equal to or less than a preset threshold B in the luminance histogram of the first image is equal to or greater than the proportion of pixels with luminance values equal to or less than the threshold B in the luminance histogram of the second image.

In other words, the image comparison unit 131 determines that the first image is darker than the second image when the proportion of pixels with a luminance value equal to or less than a preset threshold B in the luminance histogram of the first image is equal to or greater than the proportion of pixels with a luminance value equal to or less than the threshold B in the luminance histogram of the second image.

Therefore, if the image comparison unit 131 determines in step S12 that the first image is darker than the second image (YES), the process proceeds to step S13.

In step S13, the area determination unit 132 determines whether a predetermined area of the first image corresponding to a frame detected as having a scene change is a first area with a lower gradation than the preset gradation, or a second area other than the first area. Here, if the brightness is 256 gradations, the preset gradation is a brightness value of 3. Therefore, the first area is an area made up of pixels with brightness values of 0 to 3. For example, in the first image shown by reference numeral 1052 in FIG. 5, the area shown by reference numeral 1052a is one of the first areas. On the other hand, the second area is an area made up of pixels with a brightness value of 4 or more. In this way, each area may be a single pixel or a collection of multiple pixels. After the area determination is performed by the area determination unit 132, the process proceeds to steps S14 and S15.

In step S14, the first luminance value setting unit 133 sets the luminance value of the first region determined in step S13. The first luminance value setting unit 133 sets the luminance value of the first region of the first image to a luminance value within a first range of low gradations that includes the luminance value of the first region of the first image. Here, when the luminance value has 256 gradations from 0 to 255, the luminance value 3 is set as the upper limit, and the first range is set to a range of luminance values from 0 to 3.

In step S15, the second luminance value setting unit 134 sets the luminance value of the second region determined in step S13. The second luminance value setting unit 134 sets the luminance value of the second region of the first image to a luminance value within a second range that includes the luminance value of the second region of the first image and has a lower limit value that is higher than the upper limit value of the first range. Here, when the luminance value has 256 gradations from 0 to 255, the luminance value 4 is set as the lower limit value, and the second range is set as the range of luminance values from 4 to 255.

Next, a correction signal for correcting the gamma curve is generated by the correction signal generating unit 136 from the first luminance value set in step S14 and the second luminance value set in step S15 (step S18).

Next, the gamma curve generating unit 17 generates a gamma curve by correcting the input luminance of the frame in which the presence or absence of a scene change is detected based on the correction signal generated in step S18 (step S19). The generation of the gamma curve is specifically performed as follows. For example, the gamma curve (y = f(x)) of the image of scene A shown by reference numeral 1051 in FIG. 5 is set to the gamma curve shown in FIG. 6. Here, y is the output luminance value, and x is the input luminance value. Then, the gamma curve (y = f(x)) of the image of scene B shown by reference numeral 1052 in FIG. 5, which is the image after the scene change, has different settings of the output luminance value on the low gradation side and the high gradation side with the input luminance value being the threshold value Xblk. For example, on the low gradation side, the value calculated from the output luminance value of scene B is set to the output luminance value. Specifically, the luminance value set by the first luminance value setting unit 133 (luminance value 3 is the first threshold value, and the range of luminance values 0 to 3) is set to the output luminance value. On the other hand, on the high gradation side, the output luminance value is set to be between the output luminance value of scene A and the output luminance value of scene B. Specifically, the output luminance value is set to the luminance value set by the second luminance value setting unit 134 (the second threshold is a luminance value of 4 that is greater than the first threshold, and the range is luminance values of 4 to 255). The gamma curve of scene B is corrected by these output luminance values. Here, the threshold value Xblk is, for example, 30 gradations.

In a gamma curve corrected in this way, the influence of the previous frame is retained to suppress sudden changes in luminance above the threshold value Xblk, but when the luminance is below the threshold value Xblk, it is replaced with the luminance calculated from the current frame.

The panel control unit 15 sets the luminance (output luminance) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generation unit 14.

The above process creates an appropriate gamma curve for the first image that is determined to have a scene change and is determined to be a dark image. This makes it possible to immediately darken the first region, which is a low-tone region in the first image, and to gradually change the luminance of the second region, which is a region other than the low-tone region. As a result, it is possible to suppress screen flickering and whitish appearance in the low-tone region in the first image after the scene change.

On the other hand, the process for creating an appropriate gamma curve for the first image, which is determined to have a scene change and is a dark image, is as follows:

If the image comparison unit 131 determines in step S12 that the first image is not darker than the second image (NO), the process proceeds to step S16. Here, the image in which the first image is not darker than the second image is defined as the fourth image.

In step S16, the third luminance value setting unit 135 sets the luminance value of the fourth image. Specifically, the third luminance value setting unit 135 sets the number of reference frames to M using the reference frame number setting unit 1351, calculates the average value of the APL for this number of reference frames M using the average value calculation unit 1352, and sets the calculated average value of the APL as the luminance value.

Next, the process proceeds to step S18, where the correction signal generator 136 generates a correction signal for correcting the input luminance of the gamma curve of the first image based on the luminance value of the fourth image set in step S16.

Then, the gamma curve generator 17 generates a gamma curve by correcting the input luminance of the frame in which the presence or absence of a scene change has been detected based on the correction signal generated in step S18 (step S19). The panel controller 15 sets the luminance (output luminance) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generator 14.

The gamma curve generation process described above is for the case where it is determined in step S11 that there is a scene change. Below, we will explain the gamma curve generation process for the case where it is determined in step S11 that there is no scene change (NO).

That is, if it is determined in step S11 that there is no scene change (NO), the process proceeds to step S17 to set the brightness value of the third image. The third image is the image determined to have no scene change.

In step S17, the third luminance value setting unit 135 sets the luminance value of the third image. Specifically, the third luminance value setting unit 135 sets the number of reference frames to N using the reference frame number setting unit 1351, calculates the average value of the APL for this number of reference frames N using the average value calculation unit 1352, and sets the calculated average value of the APL as the luminance value.

The average APL calculated in steps S16 and S17 is the average calculated by adding the APL for each frame constituting the reference frame by the number of reference frames and dividing by the number of reference frames. Here, in the case of step S16, the number of reference frames when a scene change is detected is as follows. For example, as shown by reference numeral 1082 in FIG. 8, the frame (n+1) that was the subject of scene change detection is the current frame, and this current frame and M-1 previous frames going back from the current frame are combined to make up M. In addition, in the case of step S17, the number of reference frames when no scene change is detected is as follows. For example, as shown by reference numeral 1081 in FIG. 8, the frame (n) that was the subject of scene change detection is the current frame, and this current frame and N-1 previous frames going back from the current frame are combined to make up N. Here, N>M.

Next, the process proceeds to step S18, where the correction signal generator 136 generates a correction signal for correcting the input luminance of the gamma curve of the first image based on the luminance value of the third image set in step S17.

Then, the gamma curve generator 17 generates a gamma curve by correcting the input luminance of the frame in which the presence or absence of a scene change has been detected based on the correction signal generated in step S18 (step S19). The panel controller 15 sets the luminance (output luminance) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generator 14.

In step S11, the method of determining a scene change by comparing the histograms of the previous and next frames for each BIN to find the gradation difference and comparing the sum of the gradation differences with a preset value was described, but the method of determining a scene change is not limited to this. Other scene change determination methods may also be used.

[Modifications]
As described above, the image comparison unit 131 performs image comparison using the luminance histograms of the images before and after the scene change to determine whether the first image after the scene change is darker than the second image before the scene change. However, the determination of whether the first image is darker than the second image may be performed not using the luminance histogram but based on whether the proportion of the area below a preset gradation in the entire area of the first image is equal to or greater than a predetermined proportion.

Specifically, as shown in FIG. 9, if the ratio of the area (first area) 1091a with a preset gradation (for example, gradation 3 of 256 gradations) or less in the entire area of the first image 1091 after the scene change is equal to or greater than a predetermined ratio (for example, 1/4 of the entire area), the first image 1091 is determined to be darker than the image before the scene change. For example, if the area of the first area 1091a with gradation 3 or less in the entire area of the first image 1091 is equal to or greater than 1/3 of the area of the remaining area (second area) 1091b, the first image 1091 is determined to be darker than the second image before the scene change. Here, in FIG. 9, for convenience of explanation, the first area 1091a and the second area 1091b are rectangular areas with the same width but different heights H. Therefore, it can be seen that the height ratio of the first area 1091a, which is a black area, is 1/4 of the area of the first image 1091, since it is 1/4H.

Also, as shown in Figure 9, if the first region 1091a, which is a black area, is located at the top of the first image 1091, it can be assumed that there is a night sky, or other objects such as lines of ink letters or subtitles that are reflected in a band-like shape in the first image 1091.Also, if the first region 1091a, which is a black area, is located at the bottom of the first image 1091, it can be assumed that there is a night sea or a band in the first image 1091.

In the first embodiment, when the first image after the scene change is darker than the second image before the scene change, the first brightness value setting unit 133 sets a brightness value to prevent whiteout in black areas. However, even if the first image is not darker than the second image, the first brightness value setting unit 133 may set a brightness value. For example, if a black area exists, there is a risk that whiteout will occur in the existing black area, and in such a case, the first brightness value setting unit 133 sets a brightness value.

For example, even if the first image after the scene change is not darker than the second image before the scene change, if a black area of a predetermined shape exists, the black area will be whitish. In this case, the predetermined shape of the black area may be, for example, the shape of a "mountain" shown by reference numeral 1101 in FIG. 10, the shape of a "tree" shown by reference numeral 1102, the shape of a "person" shown by reference numeral 1103, or a square shape shown by reference numeral 1104, or a triangular shape shown by reference numeral 1105, etc. Therefore, if the black area has a predetermined shape, in order to prevent the black area from becoming whitish, even if the first image is not darker than the second image, the luminance value of the black area needs to be set by the first luminance value setting unit 133. In this case, the image comparison unit 131 judges that the first image is darker than the second image when the area below a preset gradation in the first image determined to have a scene change has a predetermined shape. As a result, the first luminance value setting unit 133 sets a luminance value of a predetermined shape.

In the following embodiment 2, an example is described in which the brightness value of the output image is set when there is a scene change, but the first image is not darker than the second image, and the first image contains a black area of a predetermined shape or a black area of a predetermined size or more.

[Embodiment 2]
Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

(Overview of the display device)
The display device 2 according to this embodiment will be described with reference to Fig. 11. Fig. 11 is a block diagram showing the configuration of the display device 2 according to this embodiment.

As shown in FIG. 11, the display device 2 has a configuration that is almost the same as that of the display device 1 of the first embodiment, except for the configuration of the brightness value setting unit 23. Therefore, in this embodiment, detailed descriptions of the configuration of the display device 2 other than the brightness value setting unit 23 will be omitted.

(Brightness value setting unit 23)
11, unlike the brightness value setting unit 13 of the first embodiment, the brightness value setting unit 23 does not include an image comparison unit 131, but includes an image judgment unit 231, an area judgment unit 132, a first brightness value setting unit 133, a second brightness value setting unit 134, a third brightness value setting unit 135, and a correction signal generation unit 136. Here, the image judgment unit 231 will be described. Note that the operations of the area judgment unit 132, the first brightness value setting unit 133, the second brightness value setting unit 134, the third brightness value setting unit 135, and the correction signal generation unit 136 are the same as those of the first embodiment, so that the description thereof will be omitted.

When the signal indicating the detection result from the scene change detection unit 12 indicates that a scene change has occurred, the image judgment unit 231 judges whether the first image for the frame that was the subject of scene change detection, i.e., the frame detected as having a scene change, is dark or not. In other words, the image judgment unit 231 does not judge whether the first image is dark or not by making a relative comparison, but makes an absolute judgment using an arbitrary criterion.

For example, the image judgment unit 231 may judge the output image to be dark when the proportion of pixels below a preset brightness value in the brightness histogram of the output image is equal to or greater than a predetermined proportion.

Alternatively, the image judgment unit 231 may judge the first image to be dark when the proportion of the area below a preset gradation in a specified area of the first image is equal to or greater than a specified proportion.

The image judgment unit 231 may also be configured to judge the first image to be a dark image when a region of the first image that is below a preset gradation has a predetermined shape. Here, the predetermined shape may be, for example, the shape of a "mountain" shown in reference numeral 1101 in FIG. 10 described in the first embodiment, the shape of a "tree" shown in reference numeral 1102, the shape of a "person" shown in reference numeral 1103, or a square shape shown in reference numeral 1104, or a triangular shape shown in reference numeral 1105, etc.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 2 having the above configuration will be described with reference to Fig. 12. Fig. 12 is a flowchart showing the flow of the gamma curve generation process. Note that this gamma curve generation process is almost the same as the flowchart shown in Fig. 3 of the first embodiment. Therefore, only step S22 which differs from the flowchart shown in Fig. 3 of the first embodiment will be described here.

In step S22, the image judgment unit 231 of the brightness value setting unit 23 judges whether the first image, which is detected as having a scene change, is dark. Here, the image judgment unit 231 judges the first image to be dark when the proportion of pixels below a preset brightness value in the brightness histogram of the first image is equal to or greater than a predetermined proportion.

In step S22, the process after the image determination unit 231 determines that the first image is dark (YES), the process after the image determination unit 231 determines that the first image is not dark (NO), and the process for an image detected in step S11 as having no sea change are the same as those in the flowchart shown in FIG. 3 of the first embodiment, and therefore will not be described.

The above process makes it possible to create an appropriate gamma curve for the first image that is determined to have a scene change and is determined to be dark. This makes it possible to immediately darken the first region, which is a low-tone region in the first image, and to gradually change the luminance of the second region, which is a region other than the low-tone region. As a result, in the output image after the scene change, it is possible to suppress screen flickering while suppressing whitish appearance in the low-tone region.

[Embodiment 3]
Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

(Overview of the display device)
The display device 3 according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a block diagram showing the configuration of the display device 3 according to this embodiment.

As shown in FIG. 13, the display device 3 has a configuration that is almost the same as that of the display device 1 of the first embodiment, except for the configuration of the brightness value setting unit 33. Therefore, in this embodiment, detailed descriptions of the configuration of the display device 3 other than the brightness value setting unit 33 will be omitted.

(Brightness value setting unit 33)
13, unlike the brightness value setting unit 13 of the first embodiment, the brightness value setting unit 33 does not include an image comparison unit 131, but includes an area determination unit 331, a first brightness value setting unit 133, a second brightness value setting unit 134, a third brightness value setting unit 332, and a correction signal generation unit 136. Here, the area determination unit 331 and the third brightness value setting unit 332 will be described. The operations of the first brightness value setting unit 133, the second brightness value setting unit 134, and the correction signal generation unit 136 are the same as those of the first embodiment, so their description will be omitted.

When the signal indicating the detection result from the scene change detection unit 12 indicates that a scene change has occurred, the area determination unit 331 determines the area as follows. For a predetermined area of the first image corresponding to the frame that was the subject of scene change detection, i.e., the frame that was detected as having a scene change, the area is determined to be either a first area with a lower gradation than a preset gradation, or a second area other than the first area. Here, the predetermined area may be the entire area of the image, or a partial area. Furthermore, the area may be a single pixel, or a collection of multiple pixels.

The first luminance value setting unit 133 sets the luminance value of the first region determined by the region determination unit 331. The second luminance value setting unit 134 sets the luminance value of the second region determined by the region determination unit 331.

When the third luminance value setting unit 332 receives a signal indicating no scene change sent from the scene change detection unit 12, it sets the luminance value of the third image of the current frame by referring to the current frame and past frames consisting of several consecutive frames going back from the current frame.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 3 having the above configuration will be described with reference to Fig. 14. Fig. 14 is a flowchart showing the flow of the gamma curve generation process. Note that this gamma curve generation process is almost the same as the flowchart shown in Fig. 3 of the first embodiment. Therefore, only step S32 which differs from the flowchart shown in Fig. 3 of the first embodiment will be described.

In step S32, the area determination unit 331 of the brightness value setting unit 33 determines whether a specific area of the first image corresponding to a frame detected as having a scene change is a first area with a lower gradation than the preset gradation, or a second area other than the first area. Here, if the brightness is set to 256 gradations, the preset gradation is set to a brightness value of 3. Therefore, the first area is an area made up of pixels with brightness values of 0 to 3. After the area determination by the area determination unit 331, the process proceeds to steps S33 and S34.

As described above, the processes in steps S33 and S34, and the subsequent processes in steps S36 and S37 are the same as steps S14, S15, S18, and S19 in FIG. 3 of the first embodiment, respectively, and therefore will not be described. Furthermore, the process after it is determined in step S31 that there is no scene change, i.e., the process in step S35, is also the same as step S17 in FIG. 3 of the first embodiment, and therefore will not be described.

The above process creates an appropriate gamma curve for an input image that is determined to have a scene change and has areas that are determined to be dark. This makes it possible to immediately darken the first area, which is a low-tone area in the first image, and to gradually change the luminance of the second area, which is an area other than the low-tone area. As a result, in the output image after the scene change, it is possible to suppress screen flickering while also suppressing whitish casts in the low-tone areas.

[Software implementation example]
The control block of display device 1 (particularly, brightness value setting unit 13, gamma curve generation unit 14, and panel control unit 15), the control block of display device 2 (particularly, brightness value setting unit 23, gamma curve generation unit 14, and panel control unit 15), and the control block of display device 3 (particularly, brightness value setting unit 33, gamma curve generation unit 14, and panel control unit 15) may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

In the latter case, the display devices 1, 2, and 3 are provided with a computer that executes instructions of a program, which is software that realizes each function. This computer is provided with, for example, at least one processor (control device) and at least one computer-readable recording medium that stores the program. The object of the present invention is achieved by the processor reading the program from the recording medium and executing it in the computer. The processor can be, for example, a CPU (Central Processing Unit). The recording medium can be a "non-transient tangible medium," such as a ROM (Read Only Memory), tape, disk, card, semiconductor memory, programmable logic circuit, etc. The display device can also be provided with a RAM (Random Access Memory) that expands the program. The program can also be supplied to the computer via any transmission medium (such as a communication network or broadcast waves) that can transmit the program. Note that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

〔summary〕
A display device according to a first aspect of the present invention includes a scene change detection unit 12 that detects whether or not a scene has changed on a frame-by-frame basis in an input image made up of a plurality of frames, a luminance value setting unit 13 that sets a luminance value of a first image for a frame in which a scene change has been detected by the scene change detection unit 12, and a display control unit (gamma curve generation unit 14, panel control unit 15) that displays an image on a display unit based on the luminance value of the first image, and the luminance value setting unit 13 sets a gradation lower than a preset gradation for a predetermined region of the first image. The image processing apparatus includes an area determination unit 132 that determines whether the area is a first area of gradation or a second area other than the first area, a first luminance value setting unit 133 that sets the luminance value of the first area determined by the area determination unit 132 to a luminance value within a first range of low gradation that includes the luminance value of the first area of the first image, and a second luminance value setting unit 134 that sets the luminance value of the second area determined by the area determination unit 132 to a luminance value within a second range that includes the luminance value of the second area of the first image and has a lower limit value that is higher than the upper limit value of the first range.

According to the above configuration, the first luminance value setting unit sets the luminance value of a first region (low gradation region) in the first image for a frame in which a scene change is detected, the luminance value of which is lower than a preset gradation, to a luminance value within a first range of low gradations including the luminance value of the first region of the first image, and the second luminance value setting unit sets the luminance value of a second region other than the first region in the first image to a luminance value within a second range including the luminance value of the second region of the first image and having a lower limit value that is higher than the upper limit value of the first range. This makes it possible to immediately darken the first region, which is a low gradation region in the first image, and to gradually change the luminance of the second region, which is a region other than the low gradation region, so that in the first image after the scene change, it is possible to suppress whitening in the low gradation region while suppressing screen flickering.

In the display device according to aspect 2 of the present invention, in the above aspect 1, the first luminance value setting unit 133 may set the luminance value of the first region to the same luminance value as that of the first region of the first image, and the second luminance value setting unit 134 may set the second range based on first image information corresponding to the first image and second image information corresponding to a second image for a frame earlier than the frame for the first image.

According to the above configuration, the first luminance value setting unit sets the luminance value of the first region to the same luminance value as the first region of the first image, and the second luminance setting unit sets the second range based on the first image information corresponding to the first image and the second image information corresponding to the second image for a frame earlier than the frame for the first image. This makes it possible to quickly darken the first region, which is a low gradation region in the first image, in the same way as the first region of the first image, and to gradually change the luminance of the second region, which is a region other than the low gradation region, so that in the output image after a scene change, it is possible to more reliably suppress whitening in the low gradation region while suppressing screen flickering.

The display device according to aspect 3 of the present invention, in the above aspect 1, includes an image comparison unit 131 that compares the brightness of the first image with that of a second image for a frame immediately preceding a frame in which a scene change has been detected by the scene change detection unit 12, and when the image comparison unit 131 determines that the first image is darker than the second image, the area determination unit 132 determines whether a predetermined area of the first image is a first area having a gradation lower than a preset gradation or a second area other than the first area, the first luminance value setting unit 133 sets the luminance value of the first area determined by the area determination unit 132 to a luminance value within the first range, and the second luminance value setting unit 134 may set the luminance value of the second area determined by the area determination unit 132 to a luminance value within the second range.

According to the above configuration, when it is determined that the first image is darker than the second image, the first luminance value setting unit sets the luminance value of the first region in the first image to a luminance value within the first range including the luminance value of the first region of the output image, and the second luminance value setting unit sets the luminance value of the second region other than the first region in the first image to a luminance value within a second range including the luminance value of the second region of the output image and having a lower limit value of a luminance value higher than the upper limit value of the first range. This makes it possible to immediately darken the first region, which is a low-tone region in the output image that is darker than before the scene change, in the same way as the first region of the output image, and to gradually change the luminance of the second region, which is a region other than the low-tone region, so that in the output image after the scene change, it is possible to more reliably suppress whitening in the low-tone region while suppressing screen flickering.

In the display device according to aspect 4 of the present invention, in the above aspect 3, the image comparison unit 131 may determine that the first image is darker than the second image when the proportion of pixels having a luminance value equal to or less than a preset threshold in the luminance histogram of the first image is equal to or greater than the proportion of pixels having a luminance value equal to or less than the threshold in the luminance histogram of the second image.

According to the above configuration, the image comparison unit determines that the first image is darker than the second image when the proportion of pixels in the luminance histogram of the first image that are equal to or lower than a preset luminance value is equal to or greater than a predetermined proportion, which is an effective method of determination when the entire first image is dark.

The display device according to aspect 5 of the present invention may further include an image judgment unit 231 that judges whether the first image is dark or not in the above aspect 1 or 2, and when the image judgment unit 231 judges that the first image is dark, the area judgment unit 132 judges whether a predetermined area of the first image is a first area having a gradation lower than a preset gradation or a second area other than the first area, the first luminance value setting unit 133 sets the luminance value of the first area judged by the area judgment unit 132 to a luminance value within the first range, and the second luminance value setting unit 134 may set the luminance value of the second area judged by the area judgment unit 132 to a luminance value within the second range.

According to the above configuration, the image judgment judges the first image to be darker than the second image when the proportion of the area below a preset gradation in the entire area of the first image is equal to or greater than a predetermined proportion, so it is an effective judgment method when some areas are dark even if the entire image is not dark.

In the display device according to aspect 6 of the present invention, in the above aspect 5, the image judgment unit 231 may judge the first image to be dark when the proportion of pixels below a preset brightness value in the brightness histogram of the first image is equal to or greater than a predetermined proportion.

According to the above configuration, the image judgment unit judges the output image to be dark when the proportion of pixels below a preset brightness value in the brightness histogram of the first image is equal to or greater than a predetermined proportion, so that it can properly judge that the entire image is dark.

In the display device according to aspect 7 of the present invention, in the above aspect 5, the image judgment unit 231 may judge the first image to be dark when the proportion of an area below a preset gradation in a predetermined area of the first image is equal to or greater than a predetermined proportion.

According to the above configuration, the image judgment unit judges the first image to be dark when the ratio of the area below a preset gradation to a predetermined area of the first image is equal to or greater than a predetermined ratio, so that it can properly judge that the entire image is dark.

In the display device according to aspect 8 of the present invention, in the above aspect 5, the image judgment unit 231 may judge the first image to be a dark image when an area of the first image that is below a preset gradation has a predetermined shape.

According to the above configuration, the image judgment unit judges the first image to be a dark image when an area of the first image that is below a preset gradation has a predetermined shape, so this is an effective judgment method when the dark area has a predetermined shape even if the entire image is not dark.

The display method according to aspect 9 of the present invention is a display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance set according to a scene change of the input image, and is characterized in that it includes a scene change detection step for detecting the presence or absence of a scene change on a frame-by-frame basis of the input image, an area determination step for determining whether a predetermined area of a first image for a frame detected as having a scene change by the scene change detection step is a first area having a gradation lower than a preset gradation or a second area other than the first area, a first luminance value setting step for setting the luminance value of the first area determined by the area determination step to a luminance value within a first range of low gradations including the luminance value of the first area of the first image, and a second luminance value setting step for setting the luminance value of the second area determined by the area determination step to a luminance value within a second range including the luminance value of the second area of the first image and having a lower limit value of a luminance value higher than the upper limit value of the first range.

According to the above configuration, the first luminance value setting step sets the luminance value of a first region (low gradation region) in the first image for a frame in which a scene change is detected, the luminance value of which is lower than a preset gradation, to a luminance value within a first range including the luminance value of the first region of the first image, and the second luminance value setting step sets the luminance value of a second region other than the first region in the first image to a luminance value within a second range including the luminance value of the second region of the first image and having a lower limit value that is higher than the upper limit value of the first range. This makes it possible to immediately darken the first region, which is a low gradation region in the first image, and to gradually change the luminance of the second region, which is a region other than the low gradation region, so that in the output image after the scene change, it is possible to suppress screen flickering and whitening in the low gradation region.

The display device according to each aspect of the present invention may be realized by a computer. In this case, the display control program for the display device that causes the computer to operate as each unit (software element) of the display device to realize the display device on the computer, and the computer-readable recording medium on which the program is recorded, also fall within the scope of the present invention.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in the respective embodiments.

1, 2, 3 Display device 11 Image acquisition unit 12 Scene change detection unit 13 Brightness value setting unit 14 Gamma curve generation unit (display control unit)
15 Panel control unit (display control unit)
16 Display panel 17 Gamma curve generation unit 23 Luminance value setting unit 33 Luminance value setting unit 111 Memory unit 112 Analysis unit 131 Image comparison unit 132 Area determination unit 133 First luminance value setting unit 134 Second luminance value setting unit 135 Third luminance value setting unit 1351 Number of reference frames setting unit 1352 Average value calculation unit 136 Correction signal generation unit 231 Image determination unit 331 Area determination unit 332 Third luminance value setting unit B Threshold value Xblk Threshold value

Claims (12)

a scene change detection unit that detects whether or not a scene change occurs on a frame-by-frame basis in an input image that is composed of a plurality of frames;
a luminance value setting unit that sets a luminance value of a first image for a frame detected by the scene change detection unit as having a scene change;
a display control unit that displays an image on a display unit based on a luminance value of the first image,
The luminance value setting unit
an image comparison unit that compares brightness between the first image and a second image for a frame immediately before a frame detected by the scene change detection unit as having a scene change;
a region determination unit that, when the first image is determined to be darker than the second image by the image comparison unit, determines for each predetermined region of the first image whether the region is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting unit that sets the luminance value of the first region determined by the region determination unit to a luminance value within a first range of low gradations that includes the luminance value of the first region of the first image;
a second luminance value setting unit that sets the luminance value of the second region determined by the region determination unit to a luminance value within a second range that includes the luminance value of the second region of the first image and has a lower limit value of a luminance value higher than an upper limit value of the first range. The image comparison unit
The display device according to claim 1, characterized in that when the proportion of pixels having a brightness value below a predetermined threshold in the brightness histogram of the first image is equal to or greater than the proportion of pixels having a brightness value below the threshold in the brightness histogram of the second image, the first image is judged to be darker than the second image. a scene change detection unit that detects whether or not a scene change occurs on a frame-by-frame basis in an input image that is composed of a plurality of frames;
a luminance value setting unit that sets a luminance value of a first image for a frame detected by the scene change detection unit as having a scene change;
a display control unit that displays an image on a display unit based on a luminance value of the first image,
The luminance value setting unit
an image determination unit that determines whether the first image is dark;
a region determination unit that, when the first image is determined to be dark by the image determination unit, determines for each predetermined region of the first image whether the region is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting unit that sets the luminance value of the first region determined by the region determination unit to a luminance value within a first range of low gradations that includes the luminance value of the first region of the first image;
a second luminance value setting unit that sets the luminance value of the second region determined by the region determination unit to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
The image determination unit is
A display device which judges a first image to be dark when a ratio of pixels having a brightness value equal to or lower than a preset brightness value in a brightness histogram of the first image is equal to or higher than a predetermined ratio. a scene change detection unit that detects whether or not a scene change occurs on a frame-by-frame basis in an input image that is composed of a plurality of frames;
a luminance value setting unit that sets a luminance value of a first image for a frame detected by the scene change detection unit as having a scene change;
a display control unit that displays an image on a display unit based on a luminance value of the first image,
The luminance value setting unit
an image determination unit that determines whether the first image is dark;
a region determination unit that, when the first image is determined to be dark by the image determination unit, determines for each predetermined region of the first image whether the region is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting unit that sets the luminance value of the first region determined by the region determination unit to a luminance value within a first range of low gradations that includes the luminance value of the first region of the first image;
a second luminance value setting unit that sets the luminance value of the second region determined by the region determination unit to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
The image determination unit is
A display device which judges a first image to be dark when a ratio of an area below a preset gradation to a predetermined area of the first image is equal to or greater than a predetermined ratio. a scene change detection unit that detects whether or not a scene change occurs on a frame-by-frame basis in an input image that is composed of a plurality of frames;
a luminance value setting unit that sets a luminance value of a first image for a frame detected by the scene change detection unit as having a scene change;
a display control unit that displays an image on a display unit based on a luminance value of the first image,
The luminance value setting unit
an image determination unit that determines whether the first image is dark;
a region determination unit that, when the first image is determined to be dark by the image determination unit, determines for each predetermined region of the first image whether the region is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting unit that sets the luminance value of the first region determined by the region determination unit to a luminance value within a first range of low gradations that includes the luminance value of the first region of the first image;
a second luminance value setting unit that sets the luminance value of the second region determined by the region determination unit to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
The image determination unit is
A display device which judges a first image to be a dark image when an area of the first image having a gradation level equal to or lower than a preset gradation has a predetermined shape. the first luminance value setting unit sets a luminance value of the first region to the same luminance value as that of the first region of the first image;
A display device as described in any one of claims 3 to 5, characterized in that the second brightness value setting unit sets the second range based on first image information corresponding to the first image and second image information corresponding to a second image for a frame that is earlier than the frame for the first image. A display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance that is set in response to a scene change of the input image, the display method comprising the steps of:
a scene change detection step of detecting whether or not a scene change occurs in each frame of the input image;
an image comparison step of comparing brightness between a first image and a second image for a frame immediately before a frame detected as having a scene change in the scene change detection step;
a region determining step of determining, when the first image is determined to be darker than the second image in the image comparing step, whether each predetermined region of the first image for a frame detected as having a scene change in the scene change detecting step is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting step of setting the luminance value of the first region determined in the region determination step to a luminance value within a first range of low gradations including the luminance value of the first region of the first image;
a second brightness value setting step of setting the brightness value of the second area determined in the area determination step to a brightness value within a second range that includes the brightness value of the second area of the first image and has a lower limit value of a brightness value higher than an upper limit value of the first range. A display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance that is set in response to a scene change of the input image, the display method comprising the steps of:
a scene change detection step of detecting whether or not a scene change occurs in each frame of the input image;
an image determining step of determining whether the first image is dark;
a region determination step of determining, when the first image is determined to be dark in the image determination step, whether each predetermined region of the first image for a frame detected as having a scene change in the scene change detection step is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting step of setting the luminance value of the first region determined in the region determination step to a luminance value within a first range of low gradations including the luminance value of the first region of the first image;
a second luminance value setting step of setting the luminance value of the second region determined in the region determination step to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
In the image determination step,
A display method comprising determining that the first image is dark when a ratio of pixels having a brightness value equal to or lower than a preset brightness value in a brightness histogram of the first image is equal to or higher than a predetermined ratio. A display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance that is set in response to a scene change of the input image, the display method comprising the steps of:
a scene change detection step of detecting whether or not a scene change occurs in each frame of the input image;
an image determining step of determining whether the first image is dark;
a region determination step of determining, when the first image is determined to be dark in the image determination step, whether each predetermined region of the first image for a frame detected as having a scene change in the scene change detection step is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting step of setting the luminance value of the first region determined in the region determination step to a luminance value within a first range of low gradations including the luminance value of the first region of the first image;
a second luminance value setting step of setting the luminance value of the second region determined in the region determination step to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
In the image determination step,
A display method comprising determining that a first image is dark when a ratio of an area below a preset gradation to a predetermined area of the first image is equal to or greater than a predetermined ratio. A display method for displaying an output image for an input image composed of a plurality of frames on a display device based on an output luminance that is set in response to a scene change of the input image, the display method comprising the steps of:
a scene change detection step of detecting whether or not a scene change occurs in each frame of the input image;
further comprising an image determining step of determining whether the first image is dark;
a region determination step of determining, when the first image is determined to be dark in the image determination step, whether each predetermined region of the first image for a frame detected as having a scene change in the scene change detection step is a first region having a gradation lower than a preset gradation or a second region other than the first region;
a first luminance value setting step of setting the luminance value of the first region determined in the region determination step to a luminance value within a first range of low gradations including the luminance value of the first region of the first image;
a second luminance value setting step of setting the luminance value of the second region determined in the region determination step to a luminance value within a second range that includes the luminance value of the second region of the first image and has a luminance value higher than an upper limit value of the first range as a lower limit value ,
In the image determination step,
A display method comprising: judging the first image to be a dark image when an area of the first image having a gradation below a preset value has a predetermined shape. A control program for causing a computer to function as the display device according to claim 1, the control program causing the computer to function as the scene change detection unit, the brightness value setting unit, the display control unit, and the image comparison unit. A control program for causing a computer to function as the display device according to any one of claims 3 to 5, the control program causing the computer to function as the scene change detection unit, the brightness value setting unit, the display control unit, and the image determination unit.

Images