CN105578068B - A kind of generation method of high dynamic range images, device and mobile terminal - Google Patents

Abstract

The embodiment of the invention discloses a method, a device and a mobile terminal for generating a high dynamic range image. The method includes: calculating a brightness-weighted average value of the current cached image, wherein the weight of an area whose brightness value is higher than a first brightness threshold is higher than that of other areas; and controlling the camera to capture an image according to an exposure parameter determined by the brightness-weighted average value , as an image to be processed; increasing the brightness of a region whose brightness value is lower than a second brightness threshold in the image to be processed, and generating an HDR image. The embodiment of the present invention can effectively improve the dynamic range of the HDR image by adopting the above technical solution, and the method does not need to take multiple photos to synthesize the HDR image, which can increase the processing speed and realize fast photographing.

Description

A high dynamic range image generation method, device and mobile terminal

technical field

Embodiments of the present invention relate to the technical field of image processing, and in particular to a method, device and mobile terminal for generating a high dynamic range image.

Background technique

Compared with ordinary images, high dynamic range (High Dynamic Range, HDR) images can provide more dynamic range and image details, and can better reflect the visual effect of people in the real environment.

At present, many mobile terminals such as digital cameras and mobile phones equipped with cameras support the HDR camera mode, which is especially suitable for taking pictures in a backlit shooting environment. When the current environment is backlit, due to the lack of dynamic range in the normal camera mode, the photos taken often have the problem of overexposure in bright areas or underexposure in dark areas. Using HDR camera mode can effectively improve this problem.

In the existing HDR camera mode, it is usually necessary to take a plurality of photos of the same scene with different exposure levels, and synthesize these photos to generate an HDR image. For example, take three photos with brighter brightness, medium brightness and darker brightness respectively. When compositing through software, the relatively underexposed part of the image in the medium brightness photo will be replaced by the corresponding part of the image in the brighter photo, while the relative exposure The excessive part of the image is replaced by the corresponding part of the image in the darker photo, and finally the HDR image is synthesized. This solution needs to take multiple photos with different brightness, which is slow and cannot meet the needs of users.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a method, device and mobile terminal for generating a high dynamic range image, so as to solve the problem of slow processing speed of the existing high dynamic range image generation scheme.

In a first aspect, an embodiment of the present invention provides a method for generating a high dynamic range image, including:

Calculating the brightness weighted average value of the current cached image, wherein the weight of the region whose brightness value is higher than the first brightness threshold is higher than the weight of other regions;

Control the camera to capture an image according to the exposure parameters determined by the brightness weighted average value as the image to be processed;

Raise the brightness of an area whose brightness value is lower than the second brightness threshold in the image to be processed, and generate an HDR image.

In a second aspect, an embodiment of the present invention provides a device for generating a high dynamic range image, including:

The brightness weighted average calculation module is used to calculate the brightness weighted average of the current cached image, wherein the weight of the region whose brightness value is higher than the first brightness threshold is higher than the weight of other regions;

An image capture control module, configured to control the camera to capture an image as an image to be processed according to the exposure parameters determined by the brightness weighted average;

The HDR image generation module is configured to increase the brightness of an area whose brightness value is lower than the second brightness threshold in the image to be processed, and generate an HDR image.

In a third aspect, an embodiment of the present invention further provides a mobile terminal integrated with the foregoing high dynamic range image generating device.

The high dynamic range image generation scheme provided in the embodiment of the present invention calculates the brightness weighted average value of the current cached image, and increases the weight of the area whose brightness value is higher than the first brightness threshold, compared with the calculation of brightness in the existing scheme On average, the calculated overall brightness value of the image is higher, and the exposure parameters determined based on this can ensure that when the camera is controlled to capture the image, the bright area will not be overexposed. The image captured with the above exposure parameters is used as the image to be processed, and the brightness of the region whose brightness value is lower than the second brightness threshold in the image to be processed is increased, and an HDR image is generated, which can effectively improve the dynamic range of the HDR image, and this solution does not require Taking multiple photos to synthesize HDR images can improve the processing speed and achieve fast photo taking.

Description of drawings

FIG. 1 is a schematic flowchart of a method for generating a high dynamic range image provided by Embodiment 1 of the present invention;

FIG. 2 is a schematic flowchart of a method for generating a high dynamic range image provided by Embodiment 2 of the present invention;

FIG. 3 is a schematic flowchart of a preferred method for generating a high dynamic range image provided by Embodiment 3 of the present invention;

FIG. 4 is a structural block diagram of an apparatus for generating a high dynamic range image according to Embodiment 4 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, only some structures related to the present invention are shown in the drawings but not all structures.

Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the steps as sequential processing, many of the steps may be performed in parallel, concurrently, or simultaneously. Additionally, the order of steps may be rearranged. The process may be terminated when its operations are complete, but may also have additional steps not included in the figure. The processing may correspond to a method, function, procedure, subroutine, subroutine, or the like.

Embodiment one

Fig. 1 is a schematic flowchart of a method for generating a high dynamic range image provided by Embodiment 1 of the present invention, the method can be executed by a device for generating a high dynamic range image, wherein the device can be implemented by software and/or hardware, and generally can be integrated in the mobile terminal. As shown in Figure 1, the method includes:

Step 101. Calculate the brightness weighted average value of the current cached image.

Wherein, weights of regions whose luminance values are higher than the first luminance threshold are higher than weights of other regions.

Exemplarily, the mobile terminal in this embodiment may specifically be a terminal such as a mobile phone, a tablet computer, and a digital camera, preferably a smart phone.

Exemplarily, the current cached image may be divided into multiple regions according to the brightness distribution, and each region may include one or more pixels. Exemplarily, the brightness value of an area may specifically be an average value of all pixels included in the area. The first brightness threshold can be set by default by the system, or can be set by the user according to personal habits. The first brightness threshold may be a fixed brightness value, or a dynamically adjusted brightness value. For example, when the first brightness threshold is set as a dynamically adjusted brightness value, it may be set as a preset ratio value of the average brightness value of the currently cached image, such as 120%.

Exemplarily, the weights of the regions whose luminance values are higher than the first luminance threshold and the weights of other regions may also be set by default by the system, or set by the user according to personal habits.

Exemplarily, the global light metering method may be used to acquire the light metering data of the current cached image, and the light metering data may include the brightness value of each pixel.

Step 102: Control the camera to capture an image according to the exposure parameter determined by the brightness weighted average value as the image to be processed.

Exemplarily, the exposure parameters may include exposure time. In existing solutions, the overall brightness of the image is usually measured by the average brightness of the image, and the exposure time is determined according to the average brightness. In this embodiment, the brightness weighted average value calculated in step 101 is used to measure the overall brightness of the image. During the calculation process, the weight of the region whose brightness value is higher than the first brightness threshold is increased, so the brightness weighted average value is higher than The exposure time determined based on the average brightness value in the existing solution is shorter, which can ensure that when the camera is controlled to capture images according to the exposure time, the bright area will not be overexposed.

Step 103, increasing the brightness of an area whose brightness value is lower than a second brightness threshold in the image to be processed, and generating an HDR image.

Exemplarily, since the exposure time is shortened, the overall brightness of the image to be processed will decrease. In order to ensure that the details in the dark are not lost, this step performs Brightness enhancement processing to show more details in dark places. The second brightness threshold can be set by default by the system, or can be set by the user according to personal habits. The second brightness threshold may be a fixed brightness value, or a dynamically adjusted brightness value.

Exemplarily, it is possible to calculate the gamma (Gamma) parameter (such as the Gamma curve) that can adjust the dark area to an appropriate brightness, and adjust the image to be processed according to the Gamma parameter, and finally generate a wider dynamic range and more image details. HDR images.

The high dynamic range image generation method provided by Embodiment 1 of the present invention calculates the weighted average value of the brightness of the current cached image, and increases the weight of the region whose brightness value is higher than the first brightness threshold, compared with the calculation of brightness in the existing scheme On average, the calculated overall brightness value of the image is higher, and the exposure parameters determined based on this can ensure that when the camera is controlled to capture the image, the bright area will not be overexposed. The image captured with the above exposure parameters is used as the image to be processed, and the brightness of the region whose brightness value is lower than the second brightness threshold in the image to be processed is increased, and an HDR image is generated, which can effectively improve the dynamic range of the HDR image, and this method does not require Taking multiple photos to synthesize HDR images can improve the processing speed and achieve fast photo taking.

Embodiment two

Fig. 2 is a schematic flowchart of a method for generating a high dynamic range image provided by Embodiment 2 of the present invention. This embodiment is optimized on the basis of the above embodiment. In this embodiment, the step "improve the brightness in the image to be processed The brightness of the area whose value is lower than the second brightness threshold, and generate an HDR image" is optimized as follows: calculate the gamma parameter according to the brightness statistics of the image to be processed; adjust the image to be processed according to the gamma parameter to improve the brightness in the image to be processed The brightness of the area whose value is lower than the second brightness threshold is obtained to obtain a sample image; an HDR image is generated according to the sample image.

Correspondingly, the method of this embodiment includes the following steps:

Step 201. Calculate the brightness weighted average value of the current cached image.

Wherein, weights of regions whose luminance values are higher than the first luminance threshold are higher than weights of other regions.

Step 202: Control the camera to capture an image according to the exposure parameter determined by the brightness weighted average value as the image to be processed.

Step 203, calculating a gamma parameter according to the luminance statistical data of the image to be processed.

Exemplarily, the brightness statistical data of the image to be processed may include: a sub-region brightness average of the image to be processed and a brightness histogram of the image to be processed. For example, the image to be processed may be equally divided into N subregions, and the average brightness of subregion i (1≤i≤N) is the average brightness of all pixels contained in subregion i. The brightness histogram, also known as the color scale, is an image with the brightness value as the abscissa and the number of pixels as the ordinate. The brightness histogram graphically represents the number of pixels at each brightness level of the image, and shows the pixels in the image. of the distribution.

Exemplarily, the Gamma parameter may include a Gamma curve or a Gamma value. The Gamma curve is a special tone curve. When the Gamma value is equal to 1, the curve is a straight line at 45° to the coordinate axis, which means that the input and output densities are the same. Gamma values above 1 will darken the output, and Gamma values below 1 will lighten the output. In existing solutions, the Gamma parameter is usually a preset fixed value, or the corresponding Gamma parameter is directly selected according to different camera modes; in this embodiment, the Gamma parameter is recalculated according to the brightness statistics of the image to be processed, In order to facilitate subsequent adjustments to the image to be processed.

Step 204 , adjust the image to be processed according to the gamma parameter, so as to increase the brightness of the region whose brightness value is lower than the second brightness threshold in the image to be processed, and obtain a sample image.

Exemplarily, after adjusting the image to be processed according to the Gamma parameter calculated in step 203, the brightness of the dark region in the image to be processed may be increased.

Step 205, generate an HDR image according to the sample image.

In the method for generating a high dynamic range image provided by Embodiment 2 of the present invention, the Gamma parameter is calculated according to the brightness statistical data of the image to be processed, and the image to be processed is adjusted according to the Gamma parameter to increase the brightness of the dark area in the image to be processed, and finally Generating HDR images can further improve the image quality of HDR images, show more image details, and meet user needs. In addition, adjusting the image to be processed based on the luminance statistical data consumes little processor, thereby reducing processor usage and further optimizing user experience.

On the basis of the above embodiments, the step of "generating an HDR image according to the sample image" may be further optimized as: performing noise reduction processing on the sample image, and generating an HDR image. The advantage of this is that when the image to be processed is adjusted according to the Gamma parameter, noise may be introduced. In order to further improve the quality of the photo, the sample image can be denoised before generating an HDR image.

Further, a wavelet denoising algorithm and/or a multi-frame denoising algorithm may be used to perform denoising processing on the sample image and generate an HDR image. The denoising processing of the sample image by using a multi-frame denoising algorithm may specifically include: acquiring multiple other sample images before or after the current sample image, and performing synthetic denoising on the current sample image and the multiple other sample images deal with.

Preferably, multiple sample images may be denoised using a wavelet denoising algorithm, and then denoised using a multi-frame denoising algorithm to finally generate an HDR image, which may further improve the denoising effect.

Embodiment Three

Fig. 3 is a schematic flow chart of a preferred high dynamic range image generation method provided by Embodiment 3 of the present invention, which is especially suitable for the 0-second delay (Zero Second Delay, ZSD; also known as Zero Second Later, ZSL) photographing mode . As shown in Figure 3, the method includes the following steps:

Step 301. Calculate the weighted average value of brightness of the current cached image.

Wherein, weights of regions whose luminance values are higher than the first luminance threshold are higher than weights of other regions.

Exemplarily, the ZSD camera mode can be understood as what you take is what you get. The photo taken at the moment the user presses the camera button is the photo the user sees in the preview interface, which is relative to the normal mode of taking pictures. To take a picture in normal mode, after pressing the camera button, a series of processing and corrections are required, such as focusing, adjusting exposure, adjusting white balance, etc., and then encoding to generate a photo. For example, in the case of previewing 30 frames per second (Frames Per Second, fps), when the user presses the camera key, it is in the first frame, but the actually captured photo may be the image in the eighth frame. In the ZSD mode, several frames of images are cached, and the moment the user presses the camera button, the cached frames are directly extracted for encoding and a photo is generated. For example, in the case of previewing at 30fps, when the user presses the camera button, it is in the first frame, and the actually captured photo is also the image in the first frame.

Exemplarily, this step can be completed by an automatic exposure parameter control (Automatic Exposure Control, AEC) algorithm, specifically, global photometry can be used to obtain photometry data, and the brightness weighted average can be calculated according to the photometry data.

Step 302: Control the camera to capture an image according to the exposure parameter determined by the brightness weighted average value as the image to be processed.

Step 303, calculating a gamma parameter according to the luminance statistical data of the image to be processed.

Exemplarily, the Gamma parameter used to increase the brightness of the dark area in the image to be processed may be calculated by a Gamma adjustment algorithm according to the average brightness of sub-regions and the brightness histogram of the image to be processed.

Step 304 , adjust the image to be processed according to the gamma parameter, so as to increase the brightness of the area in the image to be processed whose brightness value is lower than the second brightness threshold, and obtain a sample image.

Step 305, controlling the preview interface to display the sample image in real time.

Exemplarily, the calculated Gamma parameters can be written into an Image Signal Processor (Image Signal Processor, ISP), and the ISP controls the preview interface to display the sample image in real time, so that the user can see the image with the HDR effect on the preview interface, which is convenient Users capture their favorite pictures.

Step 306 , judging whether a photographing instruction is received, if yes, execute step 307 ; otherwise, continue to execute step 306 .

Exemplarily, when the user presses the camera button (or shutter button), a camera instruction may be received.

Step 307, acquiring the current sample image displayed on the preview interface.

Step 308, perform noise reduction processing on the current sample image, and generate an HDR image.

Further, a wavelet denoising algorithm and/or a multi-frame denoising algorithm may be used to perform denoising processing on the sample image and generate an HDR image.

The high dynamic range image generation method provided by Embodiment 3 of the present invention can display sample images with HDR effects in real time on the preview interface, and is applicable to the ZSD camera mode. When the user sees the sample image he is satisfied with in the preview interface, press Press the camera button, the mobile terminal will acquire the current sample image, and perform noise reduction processing on the current sample image to generate an HDR image. This method is combined with the ZSD camera mode, allowing users to easily take HDR photos by observing the preview interface, which can further enhance the user's shooting experience.

Embodiment Four

Fig. 4 is a structural block diagram of an apparatus for generating a high dynamic range image provided in Embodiment 4 of the present invention. The apparatus can be realized by software and/or hardware, and is generally integrated in a mobile device, and can be implemented by executing a method for generating a high dynamic range image To achieve HDR photos. As shown in FIG. 4 , the device includes: a brightness weighted average calculation module 401 , an image capture control module 402 and an HDR image generation module 403 .

Wherein, the brightness weighted average calculation module 401 is used to calculate the brightness weighted average value of the current cached image, wherein the weight of the region whose brightness value is higher than the first brightness threshold is higher than the weight of other regions; the image capture control module 402 uses Based on controlling the camera to capture an image according to the exposure parameters determined by the weighted average value of the brightness, as the image to be processed; the HDR image generation module 403 is used to increase the brightness of the area in the image to be processed whose brightness value is lower than the second brightness threshold Brightness, and generate HDR images.

In the device for generating a high dynamic range image provided in Embodiment 4 of the present invention, the brightness weighted average value calculation module 401 calculates the brightness weighted average value of the current cached image, and increases the weight of the region whose brightness value is higher than the first brightness threshold value. Compared with the calculation of the average brightness value in the existing solution, the calculated overall brightness value of the image is higher, and the exposure parameters determined by the image capture control module 402 can ensure that when the camera is controlled to capture the image, the bright area will not be exposed In an excessive situation, the image captured with the above exposure parameters is used as the image to be processed, and the HDR image generation module 403 increases the brightness of the region whose brightness value is lower than the second brightness threshold in the image to be processed, and generates an HDR image, which can effectively improve the HDR. The dynamic range of the image, and this method does not need to take multiple photos to synthesize the HDR image, which can improve the processing speed and realize fast photo taking.

On the basis of the above embodiments, the HDR image generation module includes a gamma parameter calculation unit, an image adjustment unit to be processed, and an HDR image generation unit. Wherein, the gamma parameter calculation unit is used to calculate the gamma parameter according to the brightness statistical data of the image to be processed; the image to be processed adjustment unit is used to adjust the image to be processed according to the gamma parameter to improve A sample image is obtained from the brightness of an area whose brightness value is lower than a second brightness threshold in the image to be processed; an HDR image generating unit is configured to generate an HDR image according to the sample image.

On the basis of the above embodiments, the HDR image generating unit is specifically configured to: perform noise reduction processing on the sample image, and generate an HDR image.

On the basis of the above embodiments, the HDR image generation unit is specifically configured to: perform noise reduction processing on the sample image by using a wavelet noise reduction algorithm and/or a multi-frame noise reduction algorithm, and generate an HDR image.

On the basis of the above embodiments, the HDR image generation unit includes a preview interface control subunit, a current sample image acquisition subunit, and an HDR image generation subunit. Wherein, the preview interface control subunit is used to control the preview interface to display sample images in real time; the current sample image acquisition subunit is used to obtain the current sample image displayed on the preview interface when receiving a photographing instruction; the HDR image generation subunit , for generating an HDR image according to the current sample image.

On the basis of the above embodiments, the brightness statistical data of the image to be processed includes: a sub-region brightness average value of the image to be processed and a brightness histogram of the image to be processed.

Embodiment five

Embodiment 5 of the present invention provides a mobile terminal, which integrates the device for generating a high dynamic range image in the embodiment of the present invention, and can realize taking HDR photos by executing a method for generating a high dynamic range image.

Exemplarily, the mobile terminal in this embodiment may specifically be a terminal such as a mobile phone, a tablet computer, and a digital camera, preferably a smart phone.

When the user uses the mobile terminal in this embodiment to take an HDR photo, the HDR photo taken has a higher dynamic range, and the shooting speed is fast, which can improve the user's shooting experience.

The device for generating a high dynamic range image and the mobile terminal provided in the above embodiments can execute the method for generating a high dynamic range image provided in any embodiment of the present invention, and have corresponding functional modules and beneficial effects for executing the method. For technical details not exhaustively described in the foregoing embodiments, reference may be made to the method for generating a high dynamic range image provided in any embodiment of the present invention.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (13)

1. A method for generating a high dynamic range HDR image, comprising: Calculate the brightness weighted average value of the current buffered image, wherein the weight of the region whose brightness value is higher than the first brightness threshold is higher than the weight of other regions; wherein the current buffered image is divided into multiple regions according to the brightness distribution, each An area includes one or more pixels; Control the camera to capture an image according to the exposure parameters determined by the brightness weighted average value as the image to be processed; Raise the brightness of an area whose brightness value is lower than the second brightness threshold in the image to be processed, and generate an HDR image. 2. The method according to claim 1, characterized in that, increasing the brightness of the area whose brightness value is lower than the second brightness threshold in the image to be processed, and generating an HDR image, comprising: Calculating gamma parameters according to the luminance statistical data of the image to be processed; adjusting the image to be processed according to the gamma parameter, so as to increase the brightness of an area in the image to be processed whose brightness value is lower than a second brightness threshold, to obtain a sample image; An HDR image is generated from the sample image. 3. The method according to claim 2, wherein generating an HDR image according to the sample image comprises: Perform noise reduction processing on the sample image, and generate an HDR image. 4. The method according to claim 3, characterized in that, performing noise reduction processing on the sample image, and generating an HDR image, comprising: Perform noise reduction processing on the sample image by using a wavelet noise reduction algorithm and/or a multi-frame noise reduction algorithm, and generate an HDR image. 5. The method according to claim 2, wherein generating an HDR image according to the sample image comprises: Control the preview interface to display sample images in real time; When a photographing instruction is received, obtain the current sample image displayed on the preview interface; An HDR image is generated according to the current sample image. 6 . The method according to claim 2 , wherein the luminance statistical data of the image to be processed comprises: a sub-region luminance average value of the image to be processed and a luminance histogram of the image to be processed. 7. A generating device for a high dynamic range HDR image, characterized in that it comprises: The brightness weighted average calculation module is used to calculate the brightness weighted average of the current cached image, wherein the weight of the area whose brightness value is higher than the first brightness threshold is higher than the weight of other areas; wherein the current cached image is based on the brightness distribution The situation is divided into multiple regions, each region includes one or more pixels; An image capture control module, configured to control the camera to capture an image as an image to be processed according to the exposure parameters determined by the brightness weighted average; The HDR image generation module is configured to increase the brightness of an area whose brightness value is lower than the second brightness threshold in the image to be processed, and generate an HDR image. 8. The device according to claim 7, wherein the HDR image generating module comprises: A gamma parameter calculation unit, configured to calculate a gamma parameter according to the luminance statistical data of the image to be processed; an image-to-be-processed adjustment unit, configured to adjust the image-to-be-processed according to the gamma parameter, so as to increase the brightness of an area in the image-to-be-processed whose luminance value is lower than a second luminance threshold, to obtain a sample image; an HDR image generating unit, configured to generate an HDR image according to the sample image. 9. The device according to claim 8, wherein the HDR image generating unit is specifically used for: Perform noise reduction processing on the sample image, and generate an HDR image. 10. The device according to claim 9, wherein the HDR image generating unit is specifically used for: Perform noise reduction processing on the sample image by using a wavelet noise reduction algorithm and/or a multi-frame noise reduction algorithm, and generate an HDR image. 11. The device according to claim 8, wherein the HDR image generating unit comprises: The preview interface control subunit is used to control the preview interface to display sample images in real time; The current sample image acquisition subunit is configured to acquire the current sample image displayed on the preview interface when receiving the photographing instruction; The HDR image generating subunit is configured to generate an HDR image according to the current sample image. 12 . The device according to claim 8 , wherein the luminance statistical data of the image to be processed comprises: a sub-region luminance average value of the image to be processed and a luminance histogram of the image to be processed. 13 . 13. A mobile terminal, characterized in that the mobile terminal integrates the device for generating a high dynamic range HDR image according to any one of claims 7-12.