JP2010068361A - Photographic image processing method, photographic image processing program, and photographic image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photographic image processing method, a photographic image processing program and a photographic image processor for effectively emphasizing a section to be sharpened such as an outline section for photographic image data. <P>SOLUTION: The image processing method for sharpening a photographic image includes: a smoothed image generation step of generating low frequency image data by performing smoothing filter processing to original image data; an edge image generation step of generating edge image data by performing Laplacian filter processing to the original image data; a differential image generation step of generating differential image data between the original image data and the low frequency image data; a sharpening adjustment image generation step of generating the product of weighting factors associated with the pixel values of the differential image data and the pixel values of the edge image data as the sharpening adjustment image data; and a sharpening processing step of generating sharpened image data by operating the addition processing of the respective pixel values of the original image data and the sharpening adjustment image data for every corresponding pixel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photographic image processing method, a photographic image processing program, and a photographic image processing apparatus that effectively sharpen photographic image data.

  A photographic printing apparatus that performs digital exposure in which red (R), green (G), and blue (B) monochromatic light is printed on a photographic paper by overlapping exposure based on digital image data of an image taken by a digital camera. (Digital Photographic Printing Equipment) uses an image reading resolution that depends on the specifications of a scanner, digital camera, etc., and an exposure resolution that depends on the specifications of the exposure head of the exposure apparatus, etc. The pixel density is determined.

  Digital exposure has an advantageous feature that various special effects that cannot be realized by analog exposure can be imparted to image data by performing various image processing operations on digital image data captured from a scanner or the like. .

  As a typical example of the special effect, in order to recover sharpness that greatly deteriorates depending on the resolution at the time of exposure of the printer, an outline portion in the image (for example, a boundary between a background and a person, a person's A sharpening process is performed to give an emphasis to the face).

  The sharpening process is a process for clearly showing a boundary between a predetermined area and another area in the image, that is, a contour portion. Specifically, by performing processing using an arithmetic filter called a sharpening filter, For a specific pixel of interest (hereinafter, pixel data corresponding to each pixel is also simply referred to as a pixel) constituting the contour portion, an image is formed so as to increase a density difference (luminance difference) between adjacent pixels. Convert the data.

  When an image taken with a digital camera is observed, it is observed that fine granular noise is superimposed on the image. In particular, noise that is rough in the dark part of the image is conspicuous, and similar noise appears in the entire image in an image shot in a dark place without flash emission.

  These noises are caused by the characteristics of the elements such as the reset noise and dark current noise of the image sensor.The imaging environment is worse, that is, the lower the illuminance of the subject, the better the noise component. Noise is enhanced when the brightness is corrected.

  When such granular noise is present in the image data, if the sharpening process using the sharpening filter or the like is performed, not only the outline portion of the image but also the granularity of the granular noise is emphasized, and photographic paper or the like There is a problem in that the roughness of the image printed on the image is increased and the image becomes unsightly. In particular, when such a feeling of roughness appears in the human skin portion of the image, the image quality is greatly reduced.

  In order to solve such a problem, various conventional solutions have been proposed.

  The simplest solution is a smoothing process on the entire image data after the sharpening process (for example, a process of replacing the value of a pixel of interest with an average value obtained from surrounding pixels using an average filter) A method of applying However, if the smoothing process is performed on the entire image data, the emphasized contour portion is blurred, and the effect of the sharpening process is diminished.

  As another solution method, a method of first performing smoothing processing on the entire image data and then performing sharpening processing is also conceivable. However, in this case, since the detailed structure (detail) in the image data is lost by the smoothing process ahead, there is a problem that the effect of contour enhancement by the subsequent sharpening process is reduced.

Therefore, in Patent Document 1 or Patent Document 2, granular noise and contour portions included in the sharpened image data obtained by performing sharpening processing on the original image are separated by a predetermined method, and the separated contour portions are shown. A method has been proposed in which image data is multiplied by a coefficient indicating the degree of enhancement of the contour portion and integrated with the original image data.
Japanese Patent Laid-Open No. 9-091419 Japanese Patent Laid-Open No. 10-243239

  According to Patent Document 1, the granular noise and the contour portion included in the sharpened image data obtained by sharpening the original image using a Laplacian filter are separated. However, in the sharpening processing of the image by the Laplacian filter, the object is achieved by making the gradation change (gradient) of the contour portion of the subject steep, and at this time, the rising gradation change jumps over the original pixel value. A phenomenon called undershoot and overshoot occurs. Specifically, it is a phenomenon that occurs conspicuously in the contour portion where the difference in shading was originally large, and unnecessary lines appear on both sides along the original contour line (even in the vicinity of the point), increasing sharpness. Although effective, it also causes discomfort.

  On the other hand, according to Patent Document 2, sharpened image data obtained by performing sharpening processing on an original image using an unsharp mask and smoothing processing on the original image are used to suppress granular noise. The difference value with the smoothed image data is taken, and the granular noise and the contour portion are separated from the image data in which the granular noise and the contour portion indicated by the difference value stand out. However, in the sharpening process using an unsharp mask, the difference value between the image data of the original image and the image data obtained by smoothing the original image with a Gaussian filter or the like is added to the original image to emphasize the high-frequency component and sharpen it. At this time, due to the use of the smoothed image, blurring of the contour called halo occurs. Specifically, it appears more prominently as the blur intensity is increased, and the outline looks thicker. This also increases sharpness to a certain extent, but it also causes discomfort.

  The present invention provides a photographic image processing method, a photographic image processing program, and a photographic image processing apparatus that effectively enhance a portion to be sharpened, such as a contour portion, with respect to photographic image data in view of the above-described conventional drawbacks. In the point.

  In order to achieve the above object, a first characteristic configuration of a photographic image processing method according to the present invention is an image processing method for sharpening a photographic image as described in claim 1 of the document of the claims. A smoothed image generating step for generating low-frequency image data by performing smoothing filter processing on the original image data; an edge image generating step for generating edge image data by performing Laplacian filter processing on the original image data; and A difference image generation step of generating difference image data of the low-frequency image data, and a product of a weighting coefficient associated with each pixel value of the difference image data and each pixel value of the edge image data Sharpening adjustment image generation step to generate, and each pixel value of the original image data and the sharpening adjustment image data are added for each corresponding pixel to sharpen In that it includes a sharpening process step of generating image data.

  According to the above configuration, the difference image generation step generates difference image data including a halo from the difference between the original image data and the low-frequency image data after the smoothing filter processing. Further, in the edge image generation step, edge image data that is sharpened using a Laplacian filter and that has a slightly uncomfortable edge in the contour portion including overshoot and undershoot is generated.

  In addition, the sharpening adjustment image generation step integrates the weight coefficient associated with the presence / absence of the contour portion indicated by the difference image data and the intensity thereof and the edge image data, and sharpening adjustment in which the contour portion is sharpened to an appropriate strength. Image data is generated.

  Therefore, in the sharpening processing step, sharpened image data is generated by the addition processing of the original image data and the sharpened adjustment image data, and thus sharpened image data in which the contour portion is sharpened to an appropriate strength is generated. Will be able to. Moreover, since the low frequency image data and the difference image data are not added to the original image, the occurrence of halo can be avoided.

  As described in claim 2, the second feature configuration includes each pixel of the difference image data as a weighting factor associated with each pixel value of the difference image data in addition to the first feature configuration described above. A pixel value obtained by performing gamma correction with a predetermined γ value that satisfies γ> 1 is employed.

  According to the above-described configuration, the pixel values of the differential image data are gamma-corrected with a predetermined γ value that satisfies γ> 1, thereby suppressing halos included in the differential image data or suppressing granular noise. For example, the strength of the contour portion indicated by the difference image data can be corrected appropriately.

  In the third feature configuration, as described in claim 3, in addition to the first configuration described above, each pixel value of the difference image data is used as a weighting factor associated with each pixel value of the difference image data. Is a pixel value obtained by performing gamma correction on a limited pixel value obtained by limiting the above with a predetermined upper limit threshold value with a predetermined γ value satisfying γ> 1.

  According to the above-described configuration, a sharp outline that is clearly identifiable and exceeds the upper threshold value of the pixel value of the original image is displayed in the original image without being sharpened. It is possible to output in the state as it is.

  In the fourth feature configuration, in addition to any one of the first to third feature configurations described above, the sharpening adjustment image generation step includes each pixel value of the edge image data. Is a product of a limited edge pixel that is limited by a predetermined edge upper limit value and the weight coefficient, as sharpening adjustment image data.

  According to the configuration described above, in the sharpening adjustment image generation step, the presence / absence of the contour portion indicated by the difference image data and the weighting coefficient associated with the intensity are integrated with the edge image data limited by the predetermined edge upper limit value. Therefore, it is possible to avoid generation of sharpened adjustment image data that is excessively sharpened and has a sense of incongruity.

  In the fifth feature configuration, as described in claim 5, in addition to any of the first to fourth feature configurations described above, the sharpening processing step includes each pixel value of the original image data and the The method includes a leveling step for suppressing overshoot or undershoot of the edge image data included in the sharpened image data obtained by adding the sharpened adjustment image data for each corresponding pixel.

  According to the above configuration, since the overshooting or undershooting is suppressed by the leveling step, it is possible to generate sharpened image data having no sense of incongruity in the contour portion.

  In the sixth feature configuration, as described in claim 6, in addition to the fifth feature configuration described above, the leveling step corresponds to each pixel value of the original image data and the sharpening adjustment image data. A sharpening-suppressed image in which the sharpened image data subjected to addition processing for each pixel to be processed is limited by the maximum value or the minimum value of the original image in a predetermined area with each pixel as a target pixel, and the sharpening-suppressed image is overshot Alternatively, the method includes a leveling process step in which correction is performed at an allowable rate corresponding to each direction based on the degree of undershoot.

  According to the above-described configuration, when the sharpened image data exceeds the maximum value or the minimum value of the original image in a predetermined area in which each pixel of the sharpened image data is the target pixel, the original image is processed by the leveling process step. It is possible to generate a sharpening-suppressed image that is limited so as not to exceed the maximum value or the minimum value, and to avoid excessively sharpening the original image.

  In addition, since the leveling processing step can correct the sharpening suppression image based on the degree of overshoot or undershoot, the overshoot or undershoot is moderately suppressed, and the sharpening without a sense of incongruity in the contour portion Image data can be generated.

  The characteristic configuration of the photographic image processing program according to the present invention is an image processing program for sharpening a photographic image as described in claim 7, wherein the low-frequency image data is generated by smoothing the original image data. A smoothed image generating step, an edge image generating step for generating edge image data by performing Laplacian filter processing on the original image data, and a difference image generating step for generating difference image data between the original image data and the low-frequency image data A sharpening adjustment image generating step for generating a product of a weighting coefficient associated with each pixel value of the difference image data and each pixel value of the edge image data as sharpening adjustment image data; and each pixel of the original image data A sharpening processing step of generating a sharpened image data by adding a value and the sharpened adjustment image data for each corresponding pixel; In that cause a computer to execute the certain.

  The photographic image processing apparatus according to the present invention is characterized in that, as described in claim 8, the photographic image processing apparatus sharpens a photographic image and generates low-frequency image data by smoothing and filtering the original image data. A smoothed image generating unit that performs Laplacian filter processing of the original image data to generate edge image data, a difference image generating unit that generates difference image data of the original image data and the low-frequency image data, and A sharpening adjustment image generating unit that generates a product of a weighting factor associated with each pixel value of the difference image data and each pixel value of the edge image data as sharpening adjustment image data; and each pixel of the original image data And a sharpening processing unit that generates a sharpened image data by adding the value and the sharpened adjustment image data for each corresponding pixel.

  As described above, according to the present invention, there are provided a photographic image processing method, a photographic image processing program, and a photographic image processing apparatus that effectively enhance a portion to be sharpened such as a contour portion with respect to photographic image data. I was able to do it.

  Embodiments of a photographic image processing apparatus according to the present invention will be described below.

  As shown in FIG. 1, a photographic image processing apparatus 1 performs an exposure process based on output image data on a photographic paper P, develops the exposed photographic paper, and generates and outputs a photographic print. And an operation station 3 for setting and inputting print order information for the photographic image, performing various image correction processes, and outputting output image data edited from the original image to the photographic printer 2.

  The operation station 3 includes a film scanner 31 that reads an image from a developed photographic film F, and a media driver that reads image data from an image data storage medium M such as a memory card in which image data shot by a digital still camera or the like is stored. 32, a general-purpose computer as the controller 33, and the like.

  As shown in FIGS. 1 and 2, the photographic printer 2 has two systems of photographic paper magazines 21 containing roll-shaped photographic paper P, and the photographic paper P drawn from the photographic paper magazine 21 in a predetermined print size. A sheet cutter 22 for cutting, a back print unit 23 for printing print information such as a frame number on the back of the cut photographic paper P, an exposure unit 24 for exposing the photographic paper P based on the print data, and a post-exposure unit A development processing unit 25 including a plurality of processing tanks 25a, 25b, and 25c filled with processing solutions for developing, bleaching, and fixing the photographic paper P is disposed along the conveyance path of the photographic paper P, and development processing is performed. A lateral feed conveyor 26 that discharges the photographic paper P that has been dried later, and a sorter 27 that sorts a plurality of photographic papers (photo prints) P stacked on the lateral feed conveyor 26 in order units. To have.

  The exposure unit 24 outputs a three-color laser beam bundle of RGB that is modulated based on the print data in the main scanning direction orthogonal to the conveyance direction with respect to the photographic paper P conveyed in the sub-scanning direction by the conveyance mechanism 28. Then, an exposure head 24a for exposure is accommodated.

  A transport mechanism 28 composed of a plurality of roller pairs that transport the printing paper P at a predetermined process speed is disposed in the exposure unit 24 and the development processing unit 25 disposed along the transport path. A chucker-type transport mechanism 28a capable of transporting the paper P in multiple rows is provided.

  A controller 33 provided in the operation station 3 operates under the management of a general-purpose operating system, and is installed with a plurality of application programs for executing various image processing and input / output control of the photo processing apparatus 1. As an operation interface, a monitor 34, a keyboard 35, a mouse 36, and the like are connected. The application program includes an image processing program according to the present invention.

  The controller 33 is a block in which the hardware and software cooperate to execute a photo processing process, and will be described below in each functional block.

  As shown in FIG. 3, the controller 33 receives photographic image data as an original image read by the film scanner 31 or the media driver 32, performs a predetermined preprocessing, and transfers it to the memory 41. A print operation information and image editing information is displayed on the screen of the monitor 34, and a graphic operation screen for displaying operation icons for inputting necessary data is generated for the print operation information or a keyboard for the displayed graphic operation screen. 35, a graphic user interface unit 42 that generates various control commands based on input operations from the mouse 36, photographic image data transferred from the image input unit 40, photographic image data after correction processing by the image processing unit 47, Correction parameters at that time, and also set A memory 41 in which lint order information is partitioned and stored in a predetermined area, an order processing unit 43 that generates print order information, and each frame image or a predetermined number of frames for each photographic image data stored in the memory 41 An image processing unit 47 that performs density correction processing, contrast correction processing, and the like on the image is provided.

  Further, a display control unit 46 including a video RAM for displaying the image data developed in the memory 41 based on a display command from the graphic user interface unit 42 and various input / output graphic data on the monitor 34, and the like; A print data generation unit 44 that generates print data for outputting the final corrected image for which various correction processes have been completed to the photographic printer 2, and a storage medium such as a CD-R for the final corrected image according to the customer's order A formatter unit 45 for converting to a file format for writing to the file.

  The film scanner 31 is configured to operate in two modes: a pre-scan mode for reading an image recorded on the film F at a high speed although it is a low resolution and a main scan mode for reading at a high resolution although it is a low resolution. Various correction processes are performed on the low-resolution image read in the mode, and the final correction for the high-resolution image read in the main scan mode based on the correction parameters stored in the memory 41 at that time. The process is executed and output to the printer 2.

  Similarly, the image file read from the media driver 32 includes a high-resolution captured image and its thumbnail image, and various correction processes described later are performed on the thumbnail image and stored in the memory 41 at that time. Based on the correction parameters, the final correction processing for the high-resolution captured image is executed. When the thumbnail image is not included in the image file, the thumbnail image is generated from the high-resolution captured image by the image input unit 40 and transferred to the memory 41.

  As described above, various editing processes that are frequently trial and error are performed on low-resolution images, so that the calculation load of the controller 33 is reduced.

  The image processing unit 47 includes a distortion correction unit 50 that corrects distortion caused by the photographic lens with respect to photographic image data that is an original image stored in the memory 41, and a granular noise suppression processing unit 51 that suppresses granular noise. A sharpening processing unit 52 that enhances an edge of an image and suppresses noise, a color correction unit 53 that adjusts a color balance so as to reproduce a natural color, and an image size suitable for the size of a photographic print A plurality of image processing blocks such as the enlargement / reduction processing unit 54 are provided.

  The sharpening processing unit 52 sharpens the image data read from the photographic film F in the main scan mode in accordance with the resolution depending on the specifications of the photographic printer 2, and the sharpening processing unit 52 for film image according to the present invention. And a sharpening processing unit 52 for a captured image of a digital camera that sharpens the high-resolution image data read from the media driver 32 according to the resolution depending on the specifications of the photographic printer 2. ing.

  Hereinafter, processing of photographic image data taken by a digital camera input from the media driver 32 will be described in detail. However, photographic image data read from the photographic film F in the main scan mode can be processed in the same manner. is there.

  When a plurality of thumbnail image data and high resolution image data read from the media driver 32 are stored in the memory 41, several frames of photographic images based on the thumbnail image data and a graphic operation screen are displayed on the screen of the monitor 34. . Normally, since the digital image stored in the medium is compressed by the JPEG method, image data obtained by inverse conversion and decompression is stored.

  For each frame image displayed on the screen of the monitor 34, the order processing unit 43 sets the print conditions, that is, the number of prints, the print size, and the like through the operator's operation on the graphic operation screen.

  Further, distortion correction, granular noise suppression processing, and color correction are performed on each frame image by the image processing unit 47 through an operator's operation, and the image correction processing conditions set at this time are stored in the memory 41. The

  When the print condition setting and correction processing operations for each frame image displayed on the screen of the monitor 34 are completed, the screen is scrolled to the next screen, and the same processing is executed for all the frame images.

  When all the operation processes are completed and a print output operation is performed via the graphic operation screen, distortion correction, granular noise suppression process, and color correction process are performed on the high-resolution photographic image data stored in the memory 41. Then, image processing such as enlargement / reduction processing or sharpening processing is executed, and the image data after the image processing is converted into print data by the print data generation unit 44 and output to the photographic printer 2.

  Each of distortion correction, granular noise suppression processing, and color correction processing for high-resolution photographic image data is automatically performed based on correction processing conditions set for thumbnail images, that is, correction processing conditions stored in the memory 41. Correction processing is executed.

  Hereinafter, the sharpening processing unit 52 for the image captured by the digital camera according to the present invention will be described in detail.

  As shown in FIG. 4, the sharpening processing unit 52 includes an RGB-YCbCr conversion processing unit 510 that converts an RGB color component of each pixel constituting photographic image data into a YCbCr luminance color difference component, and an RGB-YCbCr conversion process. A smoothed image generating unit 511 that generates low-frequency image data by performing smoothing filter processing on luminance data that is a luminance component image obtained by the unit 510, and an edge that generates edge image data by performing Laplacian filter processing on the luminance data The image generation unit 512, the difference image generation unit 513 that generates difference image data of the low-frequency image data obtained from the luminance data and the smoothed image generation unit 511, and the difference image data obtained from the difference image generation unit 513 Sharpening adjustment is performed on the product of the weight coefficient associated with each pixel value and each pixel value of the edge image data obtained from the edge image generation unit 512. Sharpening adjustment image generation unit 514 generated as image data, and each pixel value of the brightness data and the sharpening adjustment image data obtained from the sharpening processing unit 515 are added for each corresponding pixel to obtain the sharpened image data. A brightness color difference component composed of a sharpening processing unit 515 for generating image data, sharpened image data obtained by the sharpening processing unit 515, and color difference data which is a color difference component image obtained by the RGB-YCbCr conversion processing unit 510 And a YCbCr-RGB conversion processing unit 518 for inversely converting the color to RGB color components.

The RGB-YCbCr conversion processing unit 510 converts the high-resolution original image data read from the memory 41 based on the following conversion formula (for example, about 8264 pixels is about 3264 pixels × 2448 pixels). Each color component of R (red), G (green), and B (blue) (hereinafter referred to as “RGB”) of each pixel constituting the pixel is converted into a luminance color difference component and stored in the memory 41.
Y = 0.29900R + 0.58700G + 0.11400B
Cb = −0.16874R−0.33126G + 0.50000B
Cr = 0.50000R-0.41869G-0.0811B

  In the smoothed image generation unit 511, smoothing filter processing is performed on the luminance data by a weighted average filter having a filter size of about 5 × 5, and low-frequency image data is generated.

  A generally used Gaussian filter is used as the weighted average filter. A Gaussian filter is a filter having a larger filter coefficient as it is closer to the center pixel within the filter size, and the filter coefficient is determined by a Gaussian function. When the standard deviation value σ of the Gaussian function is excessively small, the sharpening effect is weakened, and when the standard deviation σ is large, noise becomes conspicuous.

  For example, when the filter size is 5 × 5 and σ is 1.15, the filter coefficient BlurCoef of each pixel in the filter has a value as shown in FIG. Note that the filter coefficient values shown in FIG. 5A are merely examples, and the present invention is not limited thereto.

In addition, the low frequency image data Blur uses the parameter BlurIntensity that makes it possible to adjust the overall smoothing intensity in addition to the above-described filter coefficients, similarly to the low frequency image data used in the sharpening process using the unsharp mask. And it is comprised so that it may obtain | require from following Formula.

  Here, dat indicates the luminance data of the original image, and n indicates the filter size. For example, when the filter size is 5 × 5, n = INT (5 ÷ 2) = 2. Further, x and y represent pixel coordinates, and i and j represent pixel coordinates in the filter region, and the same meaning is given to mathematical expressions to be described later unless otherwise specified.

  In the edge image generation unit 512, sharpening processing is executed on the luminance data by a Laplacian filter having a filter size of about 5 × 5, and edge image data is generated. For example, when the filter size is 5 × 5, the filter coefficient SharpCoef of each pixel in the Laplacian filter has a value as shown in FIG.

In addition to the above-described filter coefficients, the edge image data Sharp is configured to be obtained from the following equation using a parameter SharpIntensity that enables adjustment of the overall sharpening intensity.

  In the difference image generation unit 513, difference image data is generated using a pixel value as a difference between each pixel of the luminance data and the pixel value of the low-frequency image data obtained by the smoothed image generation unit 511 corresponding to each pixel. .

In the sharpening adjustment image generation unit 514, first, according to the magnitude of the absolute value of the pixel value of the difference image data obtained by the difference image generation unit 513, that is, according to the presence / absence of the contour and its intensity, A weighting factor for adjusting the intensity is calculated. At this time, the difference absolute value Diff, which is the absolute value of the pixel value of the difference image data, is not directly used as a weighting factor, but is controlled by the upper threshold Threshold and the correction curve Gamma. That is, the weighting factor Intensity is obtained from the following equation.

  For example, as shown in FIG. 6A, the case where the correction curve Gamma is larger than 1 will be described in detail so that the weighting coefficient Intensity is convex upward.

  As a specific example, when the value of the correction curve Gamma is 2.0 and the upper limit threshold Threshold is 6, the weight coefficient Intensity when the difference absolute value Diff is 3 and when the difference absolute value Diff is 2. Contrast. The weighting factor Intensity at this time is 1/2 ^ (1/2) when the difference absolute value Diff is 3, and is 1/3 ^ (1/2) when the difference absolute value Diff is 2. It can be seen that the weight coefficient Intensity increases when the difference absolute value Diff is 3, that is, when the difference between the difference absolute values Diff is larger.

  Therefore, it can be seen that the weight coefficient Intensity increases as the strength of the contour portion of the original image increases.

  On the other hand, the case where the correction curve Gamma is set to a value smaller than 1 will be described in detail so that the weight coefficient Intensity is convex downward.

  As a specific example, for example, when the value of the correction curve Gamma is ½ and the upper limit threshold Threshold is 6, the weight when the difference absolute value Diff is 3 and when the difference absolute value Diff is 2 Contrast the coefficient Intensity. The weighting factor Intensity at this time is 1/2 ^ 2 when the difference absolute value Diff is 3, and is 1/3 ^ 2 when the difference absolute value Diff is 2, so when the difference absolute value Diff is 3. That is, when the difference between the absolute difference values Diff is larger, the weighting coefficient Intensity becomes larger, and the weighting coefficient Intensity becomes larger as the intensity of the contour portion of the original image becomes larger as in the above-described specific example. Recognize.

  Here, in the two specific examples described above, when the correction coefficient Gamma is set to a value larger than 1, the weight coefficient Intensity when the correction curve Gamma is set to a value smaller than 1 is compared, the correction curve Gamma is greater than 1. It can be seen that the weighting factor Intensity increases when the value is set.

  That is, the contour portion can be emphasized by setting the correction curve Gamma to a value larger than 1 so that the weight coefficient Intensity is convex upward. Therefore, it becomes possible to suppress halo and granular noise included in the difference image data.

  However, the weighting factor Intensity shown in FIG. 6A is merely an example, and as shown in FIG. 6B, sharpening of granular noise included in a flat image portion having no density difference is avoided. In a portion where the difference value is low, the correction curve Gamma may be set to a value smaller than 1 to suppress the weighting coefficient Intensity and adjust by applying approximate gamma correction.

Subsequently, in the sharpening adjustment image generation unit 514, in order to suppress excessive sharpening, the restriction that the pixel value of the edge image data Sharp obtained by the edge image generation unit 512 is suppressed so as not to exceed the edge upper limit value Limit. The sharpening adjustment image data SharpIntensity ′ is calculated by integrating the edge pixels and the weighting factor Intensity for adjusting the sharpness. That is, the sharpening adjustment image data SharpIntensity ′ is calculated from the following equation.

The sharpening processing unit 515 adds the luminance data dat and the sharpening adjustment image data SharpIntensity ′ adjusted with the sharpness obtained by the sharpening adjustment image generation unit 514 to generate the sharpening image data Sharp ′. . That is, the sharpened image data Sharp ′ is calculated from the following equation.

  The difference image data is a difference between the original image data and the low-frequency image data smoothed by the smoothed image generation unit 511. Therefore, the difference image data is caused by using the low-frequency image data smoothed including the contour portion. As a result, blurring of a contour called a halo occurs. Therefore, for example, as in the sharpening process using the unsharp mask, the sharpened image data that has been sharpened by the addition process of the image data and the original image data in which the contour portion of the differential image data including the halo is emphasized, A halo is included, and the contour portion feels uncomfortable.

  In the present invention, as described above, the difference image data is gamma-corrected in the sharpening adjustment image generation unit 514 and used to generate the weighting factor Intensity for adjusting the strength of the sharpening image. Since the original image is not directly added, sharpened image data Sharp ′ that does not include a halo can be generated.

As shown in FIGS. 7A and 7B, the maximum value max and the minimum value min of the original image in a region having the same size as the Laplacian filter having each pixel as a target pixel are searched for, and the sharpness corresponding to the target pixel is obtained. A sharpening-suppressed image is generated in which the pixel value of the sharpened image data Sharp 'is limited so that the pixel value does not exceed the maximum value in overshooting and the minimum value in undershooting, and the image data of the sharpening-suppressing image is Certain sharpening-suppressed image data Sharp ″ may be output as sharpened image data Sharp ′. That is, the sharpening-suppressed image data Sharp ″ is obtained by the following equation.

  Accordingly, the generated sharpening-suppressed image data Sharp ″ can suppress the undershoot and overshoot of the contour portion, and can perform a sharpening process without a sense of incongruity.

  Further, as shown in FIG. 7B, based on the degree Drct of the undershoot or overshoot, the lower limit allowable rate USratio or the upper limit allowable rate OSratio, which is the allowable rate corresponding to the direction of each chute, is used to sharpen the image. Alternatively, image data Ans in which the degree of undershoot or overshoot of the suppression-suppressed image data Sharp ″ is corrected may be generated, and the image data Ans may be output as the sharpened image data Sharp ′.

In this case, image data Ans obtained by correcting the degree of undershoot or overshoot of the sharpening-suppressed image data Sharp ″ using the lower limit allowable rate USratio or the upper limit allowable rate OSratio is obtained by the following equation.

  Here, when the shooting direction Drct is negative, it indicates undershoot, and when it is positive, it indicates overshoot. When the shooting direction is 0, overshooting is used for convenience, but undershooting may be used. Further, the lower limit allowable rate USratio or the upper limit allowable rate OSratio can be adjusted, and a value found from a sensory test or the like may be set as appropriate.

The YCbCr-RGB conversion processing unit 518 includes a color difference component obtained from the color difference data obtained by the RGB-YCbCr conversion processing unit 510 and a luminance component obtained from the sharpened image data obtained by the sharpening processing unit 515. The new luminance / color difference component after sharpening is inversely converted into an RGB color component based on the following equation and output.
R = Y−0.000007Cb + 1.401998Cr
G = Y−0.344133Cb−0.714138Cr
B = Y + 1.772003Cb + 0.000015Cr

  Below, the procedure of each process by the sharpening process part 52 mentioned above is demonstrated based on the flowchart shown in FIG.

  First, when the RGB color component data of each pixel constituting the photographic image data is input to the RGB-YCbCr conversion processing unit 510, the RGB-YCbCr conversion processing step is executed, and the luminance data which is the luminance component of the original image and Color difference data which is a color difference component of the original image is output (S1).

  When the output luminance data is input to the smoothed image generation unit 511, a smoothed image generation step (S2) is executed.

  In the smoothed image generation step (S2), smoothing filter processing is performed on the luminance data by a Gaussian filter, and the generated low-frequency image data Blur is output to the difference image generation unit 513.

  Subsequently, when the luminance data output in the RGB-YCbCr conversion processing step and the low-frequency image data Blur are input to the difference image generation unit 513, a difference image generation step (S3) is executed.

  The difference image generation step (S3) generates difference image data in which the difference between each pixel of the luminance data and the pixel value of the low-frequency image data Blur corresponding to each pixel is a pixel value, and a sharpened adjustment image generation unit 514. Output to.

  When the luminance data output in the RGB-YCbCr conversion processing step is input to the edge image generation unit 512, the edge image generation step (S4) is executed.

  In the edge image generation step (S4), the brightness data is sharpened by a Laplacian filter, and the generated edge image data Sharp is output to the sharpening adjustment image generation unit 514.

  When the difference image data output in the difference image generation step (S3) and the edge image data Sharp output in the edge image generation step (S4) are input to the sharpening adjustment image generation unit 514, the sharpening adjustment image is displayed. A generation step (S5) is executed.

  In the sharpening adjustment image generation step (S5), the sharpening is performed by integrating the limited edge pixel in which the pixel value of the edge image data Sharp does not exceed the edge upper limit value and the weight coefficient Intensity for adjusting the sharpness. Adjusted image data SharpIntensity ′ is generated and output to the sharpening processing unit 515.

  Subsequently, when the luminance data output in the RGB-YCbCr conversion processing step and the sharpening adjustment image data SharpIntensity ′ output in the sharpening adjustment image generation step (S5) are input to the sharpening processing unit 515, A sharpening process step (S6) is performed.

  The sharpening processing step (S6) includes a sharpening adjustment image addition processing step (S61) and a leveling processing step (S62). Further, the leveling process step (S62) includes a first leveling process step (S621) and a second leveling process step (S622).

  When the sharpening processing step (S6) is executed, first, the sharpening adjustment image addition processing step (S61) is executed.

  In the sharpening adjustment image addition processing step (S61), the luminance data dat and the sharpening adjustment image data SharpIntensity ′ are added to generate sharpening image data Sharp ′, which is output to the first leveling processing step (S621). To do. Note that the sharpened image data Sharp 'may be output to the YCbCr-RGB conversion processing unit 518 instead of being output to the first leveling process step (S621).

  In the first leveling process step (S621), the maximum value max and the minimum value min of the original image in a region having the same size as the Laplacian filter having each pixel as the target pixel are searched, and the sharpened image data Sharp corresponding to the target pixel is searched. A sharpening-suppressed image is generated in which the pixel value of ′ is restricted so that it does not exceed the maximum value in the case of overshooting and below the minimum value in the case of undershooting, and the sharpening suppression that is the image data of the sharpening-suppressing image is generated The image data Sharp ″ is output to the second leveling process step (S622).

  In place of outputting the sharpening-suppressed image data Sharp '' to the second leveling process step (S622), the YCbCr-RGB conversion processing unit uses the sharpening-suppressed image data Sharp '' as the sharpened image data Sharp '. You may comprise so that it may output to 518.

  The second leveling process step (S622) uses the lower limit allowable ratio USratio or the upper limit allowable ratio OSratio, which is an allowable ratio corresponding to the direction of each chute, based on the degree of undershoot or overshoot Drct. The degree of undershoot or overshoot of the suppression image data Sharp ″ is corrected and output to the YCbCr-RGB conversion processing unit 518 as sharpened image data Sharp ′.

  Further, the color difference data output in the RGB-YCbCr conversion processing step (S1) of the RGB-YCbCr conversion processing unit 510 and the sharpened image data Sharp 'output in the sharpening processing step (S6) are converted into YCbCr-RGB conversion processing. When input to the unit 518, the YCbCr-RGB conversion processing step (S7) is executed.

  In the YCbCr-RGB conversion processing step (S7), the new brightness color difference component after sharpening composed of the color difference component obtained from the color difference data and the brightness component obtained from the sharpened image data Sharp 'is reversed to the RGB color component. Convert and output.

  Each processing by the sharpening processing unit 52 described above is realized by executing a photographic image processing program of the present invention installed in a hard disk provided in the controller 33.

  That is, an image processing program for sharpening a photographic image, a smoothed image generating step (S2) for generating low-frequency image data Blur by performing smoothing filter processing on the original image data, and Laplacian filter processing on the original image data Then, an edge image generation step (S4) for generating edge image data Sharp, a difference image generation step (S3) for generating difference image data between the original image data and the low-frequency image data Blur, and each pixel value of the difference image data A sharpening adjustment image generating step (S5) for generating a product of each pixel value of the weight coefficient Intensity associated with the edge image data Sharp as the sharpening adjustment image data SharpIntensity ′, and each pixel value of the original image data and the sharpening Corresponding to the adjustment adjustment image data SharpIntensity ′ A sharpening process step (S6) for generating the sharpened image data Sharp 'by adding each time is installed via a storage medium such as a CD or DVD in which a photographic image processing program for causing the computer to execute is stored. Yes.

  For the original image data shown in FIG. 9A, the sharpened images when the values of the correction curve Gamma are set to 0.5, 1.0, and 2.0 are shown in FIGS. 9B and 9C, respectively. ) (D). 9B, 9C, and 9D, it can be seen that the outline of the hair is sharpened by the sharpening process.

  9C and 9D, when the value of the correction curve Gamma is larger than 1, that is, as shown in FIG. 9D, the outline of the leaf that is the background image becomes clear. Recognize. Also, when you enlarge and display the outlines of several separated hairs among the bundled hairs, there is no visual discomfort, but the sharpness of unnecessary lines along the hair outlines is high. I understand that

  On the other hand, comparing FIGS. 9B and 9C, when the value of the correction curve Gamma is smaller than 1, that is, as shown in FIG. 9B, the outline of the leaf that is the background image is blurred. However, it can be seen that even if the outlines of several hairs separated from the bundled hairs are enlarged, unnecessary lines along the hair outlines are hardly seen.

  Note that the above-described embodiment is merely an example of the present invention, and it is needless to say that the specific configuration and the like of each block can be changed and designed as appropriate within the scope of the effects of the present invention.

External view of photographic image processing device Illustration of photo printer Functional block diagram of photographic image processing device Functional block diagram of the sharpening processor It is explanatory drawing of the filter coefficient of filter size 5x5, (a) is explanatory drawing which illustrates the filter coefficient of a Gaussian filter, (b) is explanatory drawing which illustrates the filter coefficient of a Laplacian filter It is explanatory drawing which shows the relationship between a weighting coefficient and the absolute value of the pixel value of difference image data, (a) is explanatory drawing which shows the case where a correction curve is made larger than 1, and shows a case where a correction curve is 1 Explanatory drawing showing a case where gamma correction is approximated by mixing the case where the correction curve is larger and the case where the correction curve is smaller than 1. It is explanatory drawing of the process which suppresses overshoot and undershoot, (a) is explanatory drawing of the process which determines the maximum value and minimum value of the pixel value of the attention pixel of sharpened image data based on an original image, b) Is an explanatory view showing pixel values of sharpened image data after processing to suppress original image data and overshoot and undershoot Flowchart for explaining the processing procedure of the sharpening processing unit It is a photographic image before and after sharpening processing, (a) is a photographic image of the original image, (b) is a photographic image when the correction curve of the weighting factor is 0.5, and (c) is a correction curve of 1.0. (D) is a photographic image when the correction curve is 2.0

Explanation of symbols

1: Photo image processing device 52: Sharpening processing unit 510: RGB-YCbCr conversion processing unit 511: Smoothed image generation unit 512: Edge image generation unit 513: Difference image generation unit 514: Sharpening adjustment image generation unit 515: Sharpness Processing unit 518: YCbCr-RGB conversion processing unit S2: Smoothed image generation step S3: Difference image generation step S4: Edge image generation step S5: Sharpening adjustment image generation step S6: Sharpening processing step S62: Leveling processing step x, y: pixel coordinates i, j: pixel coordinates in the filter area dat: original image luminance data Blur: low-frequency image data Sharp: edge image data Sharp ′: sharpened image data Sharp ″: sharpening suppression Image data SharpIntensity ′: Sharpening adjustment image data Ans: Correction of the degree of shooting Image data BlurCoef: filter coefficient (smoothed image generator)
BlurIntensity: smoothing intensity adjustment parameter (smoothed image generator)
Diff: absolute value of pixel value of difference image data (difference image generation unit)
SharpCoef: Filter coefficient (edge image generation unit)
SharpIntensity: Sharpening intensity adjustment parameter (edge image generator)
Gamma: correction curve (sharpening adjustment image generation unit)
Limit: Edge upper limit (sharpening adjustment image generator)
Intensity: Weighting factor (sharpening adjustment image generation unit)
Threshold: upper limit threshold value (sharpening adjustment image generation unit)
USratio: Lower limit allowable rate (sharpening processing part)
OSratio: Upper limit allowable rate (sharpening processing unit)

Claims (8)

An image processing method for sharpening photographic images,
A smoothed image generating step for generating low-frequency image data by performing smoothing filtering on the original image data;
An edge image generation step for generating edge image data by performing Laplacian filter processing on the original image data;
A difference image generation step for generating difference image data between the original image data and the low-frequency image data;
A sharpening adjustment image generation step of generating a product of a weighting coefficient associated with each pixel value of the difference image data and each pixel value of the edge image data as sharpening adjustment image data;
A sharpening process step of adding each pixel value of the original image data and the sharpened adjustment image data for each corresponding pixel to generate sharpened image data;
An image processing method including:   The image according to claim 1, wherein a pixel value obtained by gamma-correcting each pixel value of the difference image data with a predetermined γ value satisfying γ> 1 is used as a weighting factor associated with each pixel value of the difference image data. Processing method.   As a weighting factor associated with each pixel value of the difference image data, a limited pixel value obtained by limiting each pixel value of the difference image data with a predetermined upper threshold is gamma-corrected with a predetermined γ value that satisfies γ> 1. The image processing method according to claim 1, wherein a pixel value is adopted.   The sharpening adjustment image generation step generates, as the sharpening adjustment image data, a product of the limited edge pixel obtained by limiting each pixel value of the edge image data with a predetermined edge upper limit value and the weight coefficient. An image processing method according to any one of the above.   The sharpening processing step suppresses overshoot or undershoot of the edge image data included in the sharpened image data obtained by adding each pixel value of the original image data and the sharpened adjustment image data for each corresponding pixel. 5. The image processing method according to claim 1, further comprising a leveling step.   In the leveling step, the sharpened image data obtained by adding each pixel value of the original image data and the sharpened adjustment image data for each corresponding pixel, and the maximum value of the original image in a predetermined region having each pixel as a target pixel 6. A leveling process step including generating a sharpening suppression image limited by a minimum value and correcting the sharpening suppression image with an allowable rate corresponding to each direction based on a degree of overshoot or undershoot. Image processing method. An image processing program for sharpening photographic images,
A smoothed image generating step for generating low-frequency image data by performing smoothing filtering on the original image data;
An edge image generation step for generating edge image data by performing Laplacian filter processing on the original image data;
A difference image generation step for generating difference image data between the original image data and the low-frequency image data;
A sharpening adjustment image generation step of generating a product of a weighting coefficient associated with each pixel value of the difference image data and each pixel value of the edge image data as sharpening adjustment image data;
A sharpening process step of adding each pixel value of the original image data and the sharpened adjustment image data for each corresponding pixel to generate sharpened image data;
An image processing program for causing a computer to execute. An image processing apparatus for sharpening photographic images,
A smoothed image generator for generating low-frequency image data by performing smoothing filter processing on the original image data;
An edge image generation unit that generates edge image data by performing Laplacian filter processing on the original image data;
A difference image generation unit for generating difference image data between the original image data and the low-frequency image data;
A sharpening adjustment image generating unit that generates a product of a weighting factor associated with each pixel value of the difference image data and each pixel value of the edge image data as sharpening adjustment image data;
A sharpening processing unit that generates the sharpened image data by adding each pixel value of the original image data and the sharpened adjustment image data for each corresponding pixel;
An image processing apparatus.