JP5744648B2 - Image processing apparatus, image processing method, and computer program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing method, and a computer program, and is particularly suitable for use in performing gamma correction processing on an input image.

  Conventionally, there is gamma control as a method for making an image have an optimum contrast. In performing gamma control, there is a technique for applying gamma having the same input / output characteristics (gamma curve) to the entire screen of an input image of one frame (see Patent Document 1).

  The gamma curve is an input / output characteristic of gradation for making a photographed image look the same gradation as when viewed with the naked eye when viewed on a monitor. The captured image is input to a video processing signal IC (hereinafter referred to as a DSP). The DSP adjusts the contrast of an image using a gamma curve. For example, it is assumed that an image including a human face having a monitor output level of 85%, a mountain having a monitor output level of 30%, and a human face having a monitor output level of 95% is captured. For example, the monitor output level of an image of 256 gradations (0 to 255) has a maximum value (255) of 100% and a minimum value (0) of 0%.

  If the brightness of a person's face is adjusted appropriately by exposure correction for the above-mentioned monitor output level image, the image becomes darker to the mountain. In particular, an area where the input of the gamma curve of the video camera is small has a steeper slope than a large area. For this reason, the change of the output becomes more sensitive to the change of the input, and the mountain is displayed in darkness. Therefore, it is considered to change the gamma curve as a technique for changing the level of a person's face while maintaining the gradation of the mountain. Specifically, by changing the gamma curve above a certain input level (knee point), it is possible to prevent the mountain from being displayed in darkness.

JP-A-7-143357

However, the conventional technique described above has the following problems because the changed gamma curve is adapted to the entire screen. That is, for example, when an image of the monitor output level as described above is taken, the output level of the cloud, which is appropriate when the output level is 95%, is lowered by changing the gamma curve above a certain input level. If it does so, the image of the cloud like the dark rain cloud different from the appearance will be displayed.
The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to change a gamma curve so as to suit each subject.

  The image processing apparatus according to the present invention includes a first dividing unit that divides an input image into a plurality of first divided regions, and each of the images of the first divided regions is divided into a plurality of second divided regions. A region of a gamma curve representing a gradation input / output characteristic for an image of the first divided region based on a luminance value of the image of the first divided region and a second dividing unit that divides the image into Change means for changing, first brightness range acquisition means for acquiring a brightness range corresponding to the input area of the gamma curve changed by the change means, and the second included in the first divided area. A second luminance range acquisition means for acquiring a luminance range of the second divided region located at a boundary with another first divided region different from the first divided region, The luminance range acquired by the first luminance range acquisition means; A determination unit that determines whether or not at least a part of the luminance range acquired by the second luminance range acquisition unit overlaps, and the luminance range when the determination unit determines that the luminance range overlaps Re-changing means for re-changing a partial region of the gamma curve so that there is no overlap.

  According to the present invention, when an input image is divided into a plurality of first divided regions and a gamma curve is set for each of the images of the plurality of first divided regions, the image of the first divided region is set. Are divided into a plurality of second divided regions. When the gamma curve for the first divided region is changed, the luminance range corresponding to the input region of the changed gamma curve is at the boundary between the first divided region and the other first divided region. It is determined whether or not there is an overlap with the luminance range of the image of the second divided region. As a result of this determination, if there is an overlap in the luminance range, the gamma curve is changed again so that the overlap does not exist. Therefore, even if the image divided into the first divided areas is combined again into one image, the gamma corresponding to the image (subject) in the first divided area is reduced while reducing the luminance step near the boundary between them. A curve can be set.

It is a block diagram which shows the structure of an imaging device. It is a flowchart explaining the process of an imaging device. It is a figure which shows a 1st division area. It is a figure which shows a 2nd division area. It is a figure which shows a gamma correction curve. It is a figure which shows the relationship between the number of 2nd division areas, and a knee point. It is a figure which shows the 1st relationship between a gamma correction curve and a boundary part luminance distribution. It is a figure which shows the 2nd relationship between a gamma correction curve and a boundary part luminance distribution.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an example of the configuration of the imaging apparatus. Specifically, FIG. 1A is a diagram illustrating an example of the entire configuration of the imaging device, and FIG. 1B is a diagram illustrating an example of a detailed configuration of a DSP of the imaging device. As described above, in the present embodiment, a case where the image processing apparatus is an imaging apparatus will be described as an example.

  The imaging lens 110 is a lens for imaging an object. The aperture mechanism 120 controls the amount of incident light. The drive motor 130 drives the aperture mechanism 120. The aperture mechanism driving device 140 drives the aperture drive motor 130. The aperture position detection device 150 detects the position of the aperture mechanism 120. The sensor 200 has an image sensor that photoelectrically converts incident light. The sensor driving device 210 controls the sensor 200. For example, the sensor driving device 210 reads out a photoelectrically converted signal and controls a signal accumulation time (executes a function as a so-called electronic shutter). The sensor driving device 210 controls whether the charges output from the sensor 200 are read by addition, non-addition, or thinning out.

  The sample hold device 220 samples the signal photoelectrically converted by the sensor 200. The A / D converter 240 is an analog-digital converter that converts an analog signal into a digital signal. The first image dividing device 250 divides the image output from the A / D converter 240 into a plurality of (here, four) first divided regions. Each of the DSPs 260a to 260d is a signal processing device, and performs a process such as a color separation / color difference matrix after performing gamma correction on the image of the first divided area. Thereafter, the DSPs 260a to 260d add a synchronization signal to the processed image signal to generate a standard television signal.

  The image synthesizing device 270 synthesizes “a plurality of (four in this case) first divided region images” that have been subjected to signal processing by the DSP 260 into a single image. The recording medium 280 records “moving images and still images” obtained by the image composition device 270. The liquid crystal panel 290 displays “moving images and still images” obtained by the image composition device 270. The microcomputer 300 comprehensively controls the imaging device. For example, the microcomputer 300 issues a processing command to the aperture mechanism driving device 140, the sensor driving device 210, the DSP 260, and the like.

Next, the configuration (function) of the DSP 260 will be described. The DSPs 260a to 260d all have the same configuration (function).
The second image dividing device 261 divides each image of the first divided region divided by the first image dividing device 250 into a plurality of mesh-shaped second divided regions. The luminance value acquisition device 262 acquires the luminance value of each image of the second divided region divided by the second image dividing device 261. The input / output luminance conversion device 263 individually performs gamma correction processing on each of the “image signals of the first divided area” output from the first image dividing device 250 using the gamma correction curve (gamma curve). To apply. Then, the input / output luminance conversion device 263 outputs the “image signal of the first divided region” subjected to the gamma correction processing to the image composition device 270. The person detecting device 264 detects a person from the “first divided region image” output from the first image dividing device 250. The person can be detected, for example, by detecting the feature amount of the image in the first divided region.

Next, the configuration (function) of the microcomputer 300 will be described.
The evaluation value calculation device 301 multiplies the luminance value output from the luminance value acquisition device 262 by a weighting coefficient set for each second divided region, and calculates an index for determining whether the exposure is appropriate. To do.
The exposure control device 302 determines whether or not the exposure is appropriate based on the index calculated by the evaluation value calculation device 301, and outputs an operation command for the aperture, the electronic shutter, and the gain based on the determined result. To do.

  The input / output characteristic change amount calculation device 303 calculates a change amount of the gamma correction curve, which is an input / output characteristic, based on the luminance value output from the luminance value acquisition device 262, and outputs a command for converting the gamma correction curve. . Based on the “gamma correction curve change amount” calculated by the input / output characteristic change amount calculation device 303, the input luminance value change range acquisition device 304 specifies which range of the input gradation of the gamma correction curve is to be changed. Then, the specified range is converted into a luminance range. In the following description, this luminance range is referred to as an input luminance change range as necessary.

The input luminance distribution acquisition device 305 (gamma) of the image of the second divided region located in the “part in contact with the boundary between the first divided region and another first divided region” of the first divided region. The luminance distribution (before the correction process is performed) is acquired. This distribution shows the relationship between the luminance value and the number of second divided regions having the luminance value. In the following description, this distribution is referred to as a boundary portion luminance distribution as necessary.
The comparison device 306 compares the input luminance change range acquired by the input luminance value change range acquisition device 304 with the luminance range of the boundary portion luminance distribution acquired by the input luminance distribution acquisition device 305, and at least a part of them. It is determined whether or not they overlap each other.
When the comparison device 306 determines that the input luminance change range and the luminance range of the boundary portion luminance distribution overlap, the input / output characteristic change amount calculation device 303 prevents the gamma correction curve from being overlapped. Recalculate the amount of change.

Next, details of an example of processing of the imaging apparatus when setting a gamma correction curve will be described.
FIG. 2 is a flowchart for explaining an example of processing of the imaging apparatus when setting a gamma correction curve.
The first image dividing device 250 performs a first dividing process for dividing the image output from the A / D converter 240 into four first divided regions (step S201).
FIG. 3 is a diagram illustrating an example of the first divided region.
The image input to the first image dividing device 250 is divided into four first divided regions with the broken line (boundary line) in FIG. 3 as a boundary. The images divided into the four first divided areas 310a, 310b, 310c, and 310d are input to the DSPs 260a, 260b, 260c, and 260d, respectively. In the present embodiment, the number of “first divided region images” input to one DSP 260 is one. In the present embodiment, since the number of images in the first divided areas 310a to 310d is four, the number of DSPs 260a to 260d is four.

However, the number of images to be divided into the first divided areas by the first image dividing device 250 may be less or more than four. In that case, there are as many DSPs 260 as the number of images to be divided. Further, when the number of images to be divided exceeds the number of DSPs 260, one DSP 260 may perform processing for a plurality of images by performing time division processing.
The images of the first divided areas 310a to 310d input to the DSPs 260a to 260d are input to the second image dividing device 261, the input / output luminance conversion device 263, and the person detection device 264, respectively.
The second image dividing device 261 performs a second dividing process for dividing the image of the first divided area 310 into a finer second divided area (step S202). FIG. 4 is a diagram illustrating an example of the second divided region. Specifically, FIG. 4A is a diagram illustrating the second divided region. FIG. 4B shows the “boundary of the first divided area 310a, 301b that is the target of changing the gamma correction curve with another first divided area different from the first divided area (shown in FIG. 4). It is a figure which shows the 2nd division area located in a broken line with a thick frame.

As shown in FIG. 4A, in the present embodiment, the first divided area is divided into finer second divided areas. In the example illustrated in FIG. 4, each first divided region is divided into 128 rectangular second divided regions of 16 × 8 in length.
The luminance value acquisition device 262 acquires the luminance value of the image of each second divided region (step S203). As described above, the division into the second divided areas is for acquiring the luminance value for each second divided area. In the present embodiment, one first divided region is divided into 128 second divided regions. Therefore, the number of luminance values acquired by one DSP 260 is 128. The luminance value acquired by the luminance value acquisition device 262 is input to the input / output characteristic change amount calculation device 303 in the microcomputer 300.

  The input / output characteristic change amount calculation device 303 calculates the luminance value of the image of the first divided area (in this embodiment, based on the luminance value of the image of the second divided area included in the first divided area) A gamma correction curve is calculated (step S204) The input / output characteristic change amount calculation device 303 individually calculates a gamma correction curve for each image in the first divided region 310. A method for calculating the gamma correction curve will be described below. Fig. 5 is a diagram showing an example of a gamma correction curve, specifically Fig. 5A shows a gamma correction curve before change, and Fig. 5B shows a gamma correction curve. Fig. 5C is a diagram illustrating a gamma correction curve before and after a change, and Fig. 5C illustrates that when an image of a subject is applied to two gamma correction curves, different outputs can be obtained. It is a figure to do. , The DSP input on the horizontal axis represents the gradation of the image of the first divided region 310 input to the DSP 260, and the DSP output on the vertical axis represents the floor of the image of the first divided region 310 output from the DSP 260. Represents the key.

A first method for calculating the gamma correction curve will be described.
It is assumed that a person's face is detected by the person detection device 264 and the brightness value of the person's face is acquired by the brightness value acquisition device 262. Assume that the appropriate output brightness of the person's face is 70%. The input / output characteristic change amount calculation device 303 changes the gamma correction curve to the gamma correction curve 502 shown in FIG. 5B by changing the knee point of the gamma correction curve 501 shown in FIG. Make sure that the brightness of the face that is too bright is the appropriate face brightness.

Next, a second method for calculating the gamma correction curve will be described. This method is, for example, a method used when a human face is not detected by the human detection device 264. FIG. 6 is a diagram illustrating an example of a relationship between the number of second divided regions having a luminance value equal to or greater than a threshold and knee points.
The horizontal axis of FIG. 6 represents the number of second divided areas having a luminance value equal to or greater than a threshold value among the second divided areas included in the first divided area input to the DSP 260. The vertical axis in FIG. 6 is a knee point for changing the gamma correction curve. The range of the vertical axis in FIG. 6 corresponds to the horizontal axis (DSP input) in FIG.

  The input / output characteristic change amount calculation device 303 counts the number of second divided areas in which the luminance value of the image of the second divided area is equal to or greater than a threshold value (here, the threshold value is “150”). The input / output characteristic change amount calculation device 303 does not change the gamma correction curve regardless of the counted number of second divided areas as long as the number of counted second divided areas is 30 or less. If the counted number of the second divided areas is more than 30 and not more than 90, the input / output characteristic change amount calculation device 303 sets the knee point to “255” according to the counted number of the second divided areas. "Any value in the range of less than" 100 "or more. If the counted number of the second divided areas is greater than 90, the input / output characteristic change amount calculation device 303 sets the knee point to “100” regardless of the counted number of the second divided areas. By changing the knee point of the gamma correction curve 501 in this way, the gamma correction curve 501 is changed to, for example, gamma correction curves 502 and 503. Thus, in the present embodiment, when the number of counted second divided areas is more than 30 and not more than 90, the knee point becomes smaller as the number of counted second divided areas increases. To. In other words, the gamma correction curve is changed so that the higher the area of the high-brightness subject, the lower the brightness of the high-brightness subject.

  The input / output characteristic change amount calculation device 303 calculates (changes) the gamma correction curve as described above for each of the outputs of the four DSPs 260a to 260d (images of the first divided areas 310a to 310d). Then, the gamma correction curve relating to the image of the first divided region 310a where the face of the person whose luminance is 85% of the maximum luminance exists is, for example, a gamma correction curve 502 shown in FIG. In addition, the gamma correction curve relating to the image of the second divided region 310b in which a cloud whose luminance is 95% of the maximum luminance exists is, for example, a gamma correction curve 503 shown in FIG. Note that the gamma correction curve does not necessarily have to be changed for all the images in the first divided areas 310a to 310d.

  Here, if the gamma correction curves of the images of the two adjacent first divided regions are different, it causes a difference in luminance at the boundary between the images. For example, as shown in FIG. 5C, when the brightness of the other subject is within the input brightness change range of the gamma correction curve and the subject exists at the boundary between the images of the first divided regions 310a and 310b. To do. As a result, the luminance of the subject is different from the boundary, and a luminance step is visible. One image of the first divided area is an image that has been subjected to gamma correction processing using the gamma correction curve 501, while the image of the other first divided area uses the gamma correction curve 502. This is because the image is subjected to gamma correction processing.

In order to eliminate this luminance step, the input luminance value change range acquisition device 304 performs a first luminance range acquisition process for deriving the input luminance change range of the gamma correction curve of the image of the first divided region 310 (step S205). ).
FIG. 7 is a diagram illustrating a first example of the relationship between the gamma correction curve and the boundary portion luminance distribution. FIG. 7 is a diagram of an image of the first divided area 310a. As described above, the input luminance change range is a luminance range corresponding to the input gradation change range of the gamma correction curve. The boundary partial luminance distribution is an input image of the second divided region located in the “part contacting the boundary with another first divided region different from the first divided region” of the first divided region. This represents the relationship between the luminance value and the number of the second divided areas.

An input luminance change range R1 illustrated in FIG. 7 indicates an input luminance change range of the gamma correction curve 502 calculated for the image of the first divided region 310a. As shown in FIG. 7, the range of brightness greater than the knee point is the input brightness change range.
Next, the input luminance distribution acquisition device 305 performs a second luminance range acquisition process for deriving the boundary partial luminance distribution (step S206). The boundary partial luminance distribution here refers to the input of the second divided region located in the “part contacting the boundary with another first divided region different from the first divided region” of the first divided region. This is the relationship between the luminance value of the image and the number of the second divided areas. The boundary partial luminance distribution 701 shown in FIG. 7 is a second divided region (a portion of the first divided region 310a) located in the “part in contact with the boundary with the first divided regions 310b to 310d” of the first divided region 310a. This is a boundary portion luminance distribution for a thick frame in the image.

  The comparison device 306 inputs the input luminance change range derived by the input luminance value change range acquisition device 304 and the boundary partial luminance distribution derived by the input luminance distribution acquisition device 305. The comparison device 306 determines whether or not there is a portion overlapping the input luminance change range and the luminance range of the boundary portion luminance distribution (step S207). FIG. 7 shows that there is an overlap L between the input luminance change range R1 and the boundary portion luminance distribution 701.

  If it is determined that there is an overlap L as a result of this determination, the input / output characteristic change amount calculation device 303 re-changes the knee point with respect to the previously calculated gamma correction curve 502 in a direction in which the overlap L disappears ( Step S208). Then, the input / output characteristic change amount calculation device 303 re-changes the gamma correction curve 501 based on the changed knee point (step S204). Then, the processes of steps S204 to S208 are repeated until the overlap L disappears.

In step S208, for example, the knee point can be changed again by a preset value with the input / output resolution of the gamma correction circuit (DSP 260 (input / output luminance conversion device 263)) as the minimum unit. For example, when the overlap L is larger than the threshold, the knee point can be changed by 3 LSBs, and when the overlap L is less than or equal to the threshold, the knee point can be changed by 1 LSB.
Here, the processes in steps S204 to S208 are repeated until the overlap L disappears. However, if the overlap L can be eliminated by a single process of step S208, the process may immediately proceed to the following step S209 after the process of step S208.

When the overlap L disappears as described above, the gamma correction curve becomes, for example, a gamma correction curve 702 shown in FIG. In this example, the gamma correction curve 702 is obtained with the maximum value of the luminance range of the boundary portion luminance distribution 701 as the knee point. This is preferable because the input luminance change range can be made as large as possible, but this is not necessarily required if the gamma correction curve is re-changed so as to reduce the overlap L.
The processes in steps S204 to S208 are individually performed for all the images in the first divided area (step S209). In the example illustrated in FIG. 3, the processes in steps S <b> 204 to S <b> 208 are performed on the images of the first divided areas 310 b to 310 d in addition to the image of the first divided area 310 a. The processing in steps S204 to S208 is not necessarily performed for all the images of the first divided region 310, and is performed only for (all of) the images of the first divided region 310 that need to change the gamma correction curve 501. You may do it.

FIG. 8 is a diagram illustrating a second example of the relationship between the gamma correction curve and the boundary portion luminance distribution. FIG. 8 is a diagram of an image in the first divided area 310b.
As shown in FIG. 8, the input / output characteristic change amount calculation device 303 changes the gamma correction curve 501 to the gamma correction curve 503 (step S204). Next, the input luminance value change range acquisition device 304 derives the input luminance change range R2 of the gamma correction curve 503 (step S205).

  Next, the input luminance distribution acquisition device 305 derives a boundary partial luminance distribution 801 for the image of the first divided region 310b (step S206). The boundary partial luminance distribution 801 shown in FIG. 8 is a second divided region (first divided region) located in the “part in contact with the boundary with the first divided regions 310a, 310c, 310d” of the first divided region 310b. This is a boundary portion luminance distribution for a thick frame in the image 310b.

  Next, the comparison device 306 determines whether or not there is a portion overlapping the input luminance change range R2 and the boundary portion luminance distribution 801 (step S207). As shown in FIG. 8, the input luminance change range R2 and the boundary portion luminance distribution 801 do not overlap. Therefore, the knee point is not changed again, and the gamma correction curve for the image of the first divided region 310b is the gamma correction curve 503 (see the lowermost stage in FIG. 8).

  As described above, when the gamma correction curves for all of the images in the first divided areas 310a to 310d are determined, the input / output luminance conversion device 263 performs processing for the image in the first divided area 310 that it is responsible for. Input the gamma correction curve and perform the following process. In other words, the input / output luminance conversion device 263 performs gamma correction processing using the determined gamma correction curve so that the gradation becomes natural when displayed on the liquid crystal panel 290 or other television monitor. Then, the image of the first divided area subjected to the gamma correction processing is output from the DSPs 260a to 260d to the image composition device 270.

As described above, in the present embodiment, the input image is divided into four first divided areas, and whether or not the gamma correction curve is re-changed individually for each of the four first divided areas 310a to 310d. to decide. For example, when the gamma correction curve 501 of the image of the first divided region 310a is changed, the input luminance change range R1 of the gamma correction curve 502 after the change and the boundary portion luminance distribution 701 of the first divided region Determine whether there is any overlap. If there is an overlap L, the gamma correction curve 502 is changed again to the gamma correction curve 702 so that the overlap L disappears. Then, the re-changed gamma correction curve 702 is used as the gamma correction curve for the image of the first divided region 310a.
Therefore, even if the image divided into the first divided areas 310a to 310d is synthesized again into one image, the luminance difference generated near the boundary between them is reduced and the first divided areas 310a to 310d are reduced. An optimal gamma correction curve can be applied to each image (subject). Therefore, an image having optimal brightness and contrast as a whole can be output.

  In this embodiment, the case where an image is divided into four has been described as an example. However, if the image is divided into more first divided regions, an optimal gamma correction curve can be set for each finer area. Therefore, the luminance level difference can be further reduced at the boundary of the first divided region, and an image having more optimal brightness and contrast can be output.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

(Other examples)
The present invention is also realized by executing the following processing. That is, first, software (computer program) for realizing the functions of the above embodiments is supplied to a system or apparatus via a network or various storage media. Then, the computer (or CPU, MPU, etc.) of the system or apparatus reads and executes the computer program.

  250 First image segmentation apparatus, 260 DSP, 300 microcomputer

Claims (8)

First dividing means for dividing the input image into a plurality of first divided regions;
Second dividing means for dividing each of the images of the first divided area into a plurality of second divided areas;
Changing means for changing a partial area of a gamma curve representing an input / output characteristic of a gradation with respect to an image of the first divided area based on a luminance value of the image of the first divided area;
First luminance range acquisition means for acquiring a luminance range corresponding to the input area of the gamma curve changed by the changing means;
The luminance range of the second divided area located at the boundary with the second divided area that is included in the first divided area and different from the first divided area. Second luminance range acquisition means for acquiring
A determination unit that determines whether at least a part of the luminance range acquired by the first luminance range acquisition unit and the luminance range acquired by the second luminance range acquisition unit overlap each other;
Re-changing means for re-changing a part of the gamma curve so that the luminance ranges do not overlap when the determining means determines that the luminance ranges overlap. apparatus.   The determination unit determines whether at least a part of the luminance range acquired by the first luminance range acquisition unit and the luminance range acquired by the second luminance range acquisition unit overlap each other. The image processing apparatus according to claim 1, wherein each of the plurality of first divided areas is determined.   The second luminance range acquisition means is the second divided area included in the first divided area corresponding to the gamma curve to be changed by the changing means, and the first divided area is 3. The image processing apparatus according to claim 1, wherein a luminance range of the second divided region located at a boundary with another different first divided region is acquired. A first dividing step of dividing the input image into a plurality of first divided regions;
A second dividing step of dividing each of the images of the first divided area into a plurality of second divided areas;
A changing step of changing a partial region of a gamma curve representing an input / output characteristic of a gradation with respect to an image of the first divided region based on a luminance value of the image of the first divided region;
A first luminance range acquisition step of acquiring a luminance range corresponding to the input region of the gamma curve, changed by the changing step;
The luminance range of the second divided area located at the boundary with the second divided area that is included in the first divided area and different from the first divided area. A second luminance range acquisition step of acquiring
A determination step of determining whether at least a part of the luminance range acquired by the first luminance range acquisition step and the luminance range acquired by the second luminance range acquisition step overlap each other;
And a re-changing step of re-changing a part of the gamma curve so that the luminance ranges do not overlap when it is determined that the luminance ranges are overlapped by the determination step. Method.   In the determination step, whether or not at least a part of the luminance range acquired by the first luminance range acquisition step and the luminance range acquired by the second luminance range acquisition step overlap each other, The image processing method according to claim 4, wherein each of the plurality of first divided areas is determined.   The second luminance range acquisition step is the second divided region included in the first divided region corresponding to the gamma curve to be changed by the changing step, and the first divided region is 6. The image processing method according to claim 4, wherein a luminance range of the second divided area located at a boundary with another different first divided area is acquired. A first dividing step of dividing the input image into a plurality of first divided regions;
A second dividing step of dividing each of the images of the first divided area into a plurality of second divided areas;
A changing step of changing a partial region of a gamma curve representing an input / output characteristic of a gradation with respect to an image of the first divided region based on a luminance value of the image of the first divided region;
A first luminance range acquisition step of acquiring a luminance range corresponding to the input region of the gamma curve, changed by the changing step;
The luminance range of the second divided area located at the boundary with the second divided area that is included in the first divided area and different from the first divided area. A second luminance range acquisition step of acquiring
A determination step of determining whether at least a part of the luminance range acquired by the first luminance range acquisition step and the luminance range acquired by the second luminance range acquisition step overlap each other;
When the determination step determines that the luminance ranges overlap, the computer is caused to execute a re-change step of re-changing a part of the gamma curve so that the luminance ranges do not overlap. Computer program.   A computer-readable storage medium storing the computer program according to claim 7.

Images