JP2010256536A - Image processing device and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable designation of an image area and a gradation range on which gradation correcting processing is performed, when the gradation correcting processing is applied to an image, and to precisely enhance the detailed information to which a user desires to draw attention, by independently applying gradation correcting processing on the inside and the outside of a target area. <P>SOLUTION: An image display device has a target-area acquiring section 1 and an image dividing section 2 which set the target area in an input image; a center luminance value determining section 3, that determines a central luminance value of the set target area; an inside target area gradation correction property determining section 4, that determines gradation correction property, based on the determined central luminance value; an inside target area gradation correction calculating section 5 that performs gradation correction in the target area, based on the determined gradation correction properties; an out of target area gradation correction property determining section 6, that calculates the amount of statistics for a pixel outside the target area set in the image dividing section 2 and determines the gradation correction property, based on the calculated amount of statistics; and an out of target area gradation correction calculating section 7, that performs gradation correction outside the target area, based on the determined gradation correction property. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image display apparatus, and more particularly to an image processing apparatus and an image display apparatus having a function of performing gradation correction processing on an input image signal.

  In an image display device such as a liquid crystal display, gradation correction processing such as contrast enhancement is performed for the purpose of improving image quality. In these processes, the pixel value of the image signal is analyzed, and the correction level is dynamically changed based on the histogram and other statistics. However, it is not easy to improve the sense of contrast over the entire image, and there is a problem that detailed information tends to be lost in a dark region or a bright region, particularly for an image in which light and dark are mixed.

  For example, in Japanese Patent Application Laid-Open No. 2004-228561, a region in which an image is focused on by a user (hereinafter referred to as a region of interest) is defined in Patent Document 1, and the entire image is adjusted so that the contrast in the region of interest is improved. An adjustment device is described.

  FIG. 15 is a block diagram illustrating an example of a functional configuration of a conventional contrast adjustment apparatus. In FIG. 15, reference numeral 101 denotes an attention area setting unit, 102 denotes a gradation correction characteristic determination unit, and 103 denotes a gradation correction calculation unit. The attention area setting unit 101 sets a rectangular area at the center of the input image as the attention area. The gradation correction coefficient determination unit 102 generates a histogram of the luminance values of the input image. However, instead of using a simple frequency, pixels outside the region of interest multiplied by a coefficient smaller than 1 are used as the histogram frequency. to add. A gradation correction characteristic for controlling the degree of gradation correction is calculated using a histogram in which the contribution of pixels in the attention area created in this way is large. The tone correction calculation unit 103 performs contrast enhancement on the input image based on the created tone correction characteristics.

  FIG. 16 shows an example of the gradation correction characteristic of the conventional contrast adjusting device shown in FIG. The horizontal axis indicates the luminance value before gradation correction, and the vertical axis indicates the luminance value after gradation correction. For convenience of explanation, the luminance value indicates a normalized value, where the minimum value is 0% and the maximum value is 100%. In the gradation correction characteristic graph, the contrast is enhanced in a gradation range where the inclination is larger than 1, and the contrast is suppressed in a gradation range where the inclination is less than 1. In this example, when the horizontal axis is 77% or less, the straight line has a slope of 1.29, and the contrast within this gradation range is enhanced. When the horizontal axis is 77% or more, it is a straight line with a slope of 0, and the change in output gradation is completely suppressed within this input gradation range.

JP 2006-120030 A

  As can be seen from the example of FIG. 16, when contrast enhancement is performed, a gradation range in which the contrast is suppressed occurs separately. In other words, when a gradation range having an inclination greater than 1 is created, another gradation range in which the inclination is less than 1 is generated. For this reason, for an image in which light and dark are mixed in the attention area, the conventional contrast adjustment apparatus shown in FIG. 15 may include a gradation range in which the contrast is suppressed in the attention area. In this case, there is a problem that detailed information to be noticed is lost.

  The present invention has been made in view of the above-described circumstances. When performing gradation correction processing on an image, it is possible to specify an image region and a gradation range to be subjected to gradation correction processing. It is an object of the present invention to provide an image processing apparatus and an image display apparatus that accurately emphasize detailed information that a user wants to pay attention to by performing the image processing independently inside and outside the attention area.

  In order to solve the above problem, a first technical means is an image processing apparatus that performs gradation correction on an input image, and includes an attention area setting unit that sets an attention area on the input image, and the setting A central pixel value acquisition unit that acquires a central pixel value of the attention area that has been acquired; a gradation correction characteristic determination unit that determines gradation correction characteristics based on the acquired central pixel value; and the determined gradation correction Based on the characteristics, the in-region tone correction calculation unit that performs tone correction in the region of interest, and the statistic of the pixel value for the pixels outside the region of interest set in the region-of-interest setting unit are calculated. A non-region-of-interest gradation correction characteristic determination unit that determines a gradation correction characteristic based on a statistic of pixel values, and an area outside the region of interest that performs gradation correction outside the region of interest based on the determined gradation correction characteristic And a key correction calculator. .

  A second technical means is the first technical means, wherein the in-region tone correction characteristic determining unit calculates a statistic of a pixel value for a pixel in the attention region set by the attention region setting unit, The gradation correction characteristic is determined based on the calculated statistic of the pixel value and the central pixel value acquired by the central pixel value acquisition unit.

  A third technical means is an overall gradation in which, in the first technical means, a statistic of a pixel value is calculated for pixels of the entire input image, and a gradation correction characteristic is determined based on the calculated statistic of the pixel value. A correction characteristic determination unit; and an overall gradation correction calculation unit that performs gradation correction of the entire input image based on the determined gradation correction characteristic, and the central pixel value acquisition unit includes the overall gradation correction calculation The center pixel value of the attention area set by the attention area setting section is acquired for the entire input image whose tone has been corrected by the section.

  A fourth technical means includes a correction coefficient acquisition unit that acquires a correction coefficient for adjusting a tone correction characteristic in the attention area based on an input by a user in the first technical means, and the attention area The inner tone correction characteristic determination unit determines the tone correction characteristic based on the center pixel value acquired by the center pixel value acquisition unit and the correction coefficient acquired by the correction coefficient acquisition unit. Is.

  According to a fifth technical means, in any one of the first to fourth technical means, the attention area setting unit sets the attention area for the input image in accordance with a user operation input. It is a thing.

  A sixth technical means is any one of the first to fifth technical means, wherein the statistic is a luminance histogram.

  The seventh technical means is the attention area tracking that follows the attention area set by the attention area setting section based on a motion vector between frames of the input image in any one of the first to sixth technical means. The region-of-interest tone correction calculation unit has a tone correction characteristic determined by the region-of-interest tone correction characteristic determination unit for the region of interest tracked by the region-of-interest tracking unit. The gradation correction unit outside the region of interest performs gradation correction based on the gradation determined by the gradation correction characteristic determination unit outside of the region of interest for the outside of the region of interest tracked by the region of interest tracking unit. It is characterized by performing gradation correction based on the correction characteristics.

  According to an eighth technical means, in any one of the first to seventh technical means, the in-region gradation correction characteristic determined by the in-region gradation correction characteristic determination unit is an input in which contrast is emphasized. The center pixel value acquired by the center pixel value acquisition unit includes a brightness range and an input brightness range in which contrast is suppressed, and is included in the input brightness range in which the contrast is emphasized. is there.

  According to a ninth technical means, in any one of the sixth to eighth technical means, the out-of-focus tone correction characteristic determination unit sequentially adds the frequencies of the luminance histogram in descending order of luminance value. The maximum luminance value in which the ratio of the total frequency to the number of pixels outside the attention area does not exceed the first threshold value outside the first attention area is determined as a white saturation value, and the frequency of the luminance histogram is determined as the luminance The lowest luminance value is determined as the black saturation value so that the ratio of the total frequency to the number of pixels outside the region of interest does not exceed the second threshold value outside the region of interest specified in advance. The gradation correction characteristic is characterized in that contrast is enhanced in a range where the input luminance value is not less than the black saturation value and not more than the white saturation value.

  A tenth technical means is an image display device comprising the image processing device according to any one of the first to ninth technical means and a display unit for displaying an input image.

  According to the present invention, when performing gradation correction processing on an image, it is possible to specify an image area and gradation range for which gradation correction processing is to be performed, and the gradation correction processing can be performed independently inside and outside the attention area. By doing so, it is possible to accurately emphasize detailed information that the user wants to pay attention to.

1 is a block diagram illustrating a schematic configuration example of an image display device according to a first embodiment of the present invention. It is a figure which shows an example of the gradation correction characteristic produced in the attention area gradation correction characteristic determination part. It is a flowchart for demonstrating an example of the flow of a process of the gradation correction characteristic determination part in an attention area shown in FIG. It is a figure which shows the other example of the gradation correction characteristic produced in the attention area internal gradation correction characteristic determination part. It is a figure which shows an example of the gradation correction characteristic produced in the attention outside area | region gradation correction characteristic determination part. It is a flowchart for demonstrating an example of the flow of a process of the attention outside area | region gradation correction characteristic determination part shown in FIG. It is a figure which shows an example of the brightness | luminance histogram outside an attention area calculated by the attention area outside gradation correction characteristic determination part. It is a block diagram which shows the example of schematic structure of the image display apparatus which concerns on 2nd embodiment of this invention. It is a figure which shows the other example of the gradation correction characteristic produced in the attention area internal gradation correction characteristic determination part. It is a flowchart for demonstrating an example of the flow of a process of the gradation correction characteristic determination part in an attention area shown in FIG. It is a block diagram which shows the example of schematic structure of the image display apparatus which concerns on 3rd embodiment of this invention. It is a block diagram which shows the example of schematic structure of the image display apparatus which concerns on 4th embodiment of this invention. It is a figure which shows an example of the gradation correction characteristic produced in the attention area gradation correction characteristic determination part. It is a block diagram which shows the schematic structural example of the image display apparatus which concerns on 5th embodiment of this invention. It is a block diagram which shows an example of a functional structure of the conventional contrast adjustment apparatus. It is a figure which shows an example of the gradation correction characteristic produced with the conventional contrast adjustment apparatus.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an image processing device and an image display device according to the invention will be described with reference to the accompanying drawings by exemplifying an image display device including an image processing device and a display unit. In addition, in each drawing of each embodiment, the part which has the same function is attached | subjected the same code | symbol, and repeated description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration example of an image display apparatus according to the first embodiment of the present invention, in which 1 is a region of interest position acquisition unit, 2 is an image dividing unit, and 3 is a central luminance value determination. , 4 is a tone correction characteristic determination unit within the region of interest, 5 is a tone correction calculation unit within the region of interest, 6 is a tone correction property determination unit outside the region of interest, 7 is a tone correction calculation unit outside the region of interest, and 8 is A display part is shown.

  The attention area position acquisition unit 1 acquires the attention area position in response to an input from the user, and outputs this to the image division unit 2 and the central luminance value determination unit 3. Hereinafter, the shape of the attention area will be described by taking a circular shape as an example. The circle can be specified by the center and the radius. For example, when the display unit 8 has a touch panel function, the center position is determined by the user at the center of the area that the user wants to pay attention to in the display image on the screen. Acquired by instructing using the touch panel. For example, the user may instruct using a remote controller. Or you may use the image position calculated from the gaze direction of the user detected with the gaze detection apparatus which is not shown in figure. The radius may be instructed by the user through a touch panel, a remote controller, or other input device (not shown), or may be a fixed value set in advance. Note that the shape of the attention area is not limited to a circle, and may be another shape such as an ellipse or a rectangle.

  Based on the attention area position acquired by the attention area position acquisition section 1, the image dividing section 2 divides all the pixels of the input image into two, the inside of the attention area and the outside of the attention area. When the center and radius of the circle are input, the circumference and the pixels included in the circumference are set as the attention area, and the other pixels are set as the outside of the attention area. The result of the division is output, for example, as a binary mask image with “1” inside the attention area and “0” outside the attention area. The attention area position acquisition unit 1 and the image dividing unit 2 correspond to an attention area setting unit.

  The central luminance value determination unit 3 corresponds to the central pixel value acquisition unit, acquires the corresponding pixel value of the input image based on the attention region position acquired by the attention region position acquisition unit 1, and determines the central luminance value. . For example, the median of the brightness value is calculated for 5 pixels vertically and horizontally (total 25 pixels) with the center coordinate of the circle as the center, and this is used as the center brightness value. Other statistics such as an average value or a weighted average value may be used instead of the median. Further, instead of the vertical and horizontal 5 pixels, other regions such as vertical and horizontal 3 pixels may be used, or only one pixel may be used.

  The attention area gradation correction characteristic determination unit 4 creates a gradation correction characteristic for emphasizing the gradation in the vicinity of the central luminance value determined by the central luminance value determination unit 3. FIG. 2 is a graph showing an example of the in-region gradation correction characteristic created by the in-region gradation correction characteristic determination unit 4. Similar to FIG. 16 described above, the horizontal axis represents the luminance value before correction (%), and the vertical axis represents the luminance value after correction (%). In the figure, c is a central luminance value input to the in-region gradation correction characteristic determination unit 4, and w is a preset enhanced luminance width. “a” is a preset enhancement level (a> 1), and the gradation correction characteristic is determined so that the slope is “a” in the range of the input luminance value from c−w / 2 to c + w / 2. Thereby, the contrast of the gradation near the central luminance value c is enhanced, and the greater the value of a, the stronger the enhancement. In the remaining range of the horizontal axis, the slope is b, and b is calculated from a and w using the following equation.

b = (100−wa) / (100−w) (1)
Since b <1, the contrast is suppressed within the gradation range where the inclination is b. The gradation correction characteristic graph is created by a broken line composed of three straight lines. The polygonal line is created so as to pass through the origin and (100, 100) and monotonously increase. However, it is necessary to set a and w in advance so that b is 0 or more.

  FIG. 3 shows an example of the flow of processing in the in-region tone correction characteristic determination unit 4. First, the inclination b is calculated from the central luminance value c, the enhanced luminance width w, and the enhanced level a using Equation (1) (step S1). Then, an equation of three straight lines constituting the graph of FIG. 2 is calculated (step S2). Since this calculation method is clear, a description thereof will be omitted. Finally, a look-up table (LUT) describing the tone correction characteristics is created and output (step S3).

  If c−w / 2 <0 or c + w / 2> 100, correction is necessary. As a correction method, when cw / 2 <0, for example, when calculating b, the following equation is used instead of equation (1).

b = {100− (c + w / 2) a} / {100− (c + w / 2)} Expression (2)
An example of the gradation correction characteristic in the case of c−w / 2 <0 is shown in FIG. Further, the correction is performed in the same manner for the case of c + w / 2> 100. The correction method is not limited to this example, and the values of c and w may be corrected directly.

  In FIG. 1, the in-region gradation correction calculation unit 5 records the in-region gradation correction characteristic created by the in-region gradation correction characteristic determination unit 4 for the luminance value of the pixel in the region of interest. The gradation correction is performed based on the LUT and the result is output to the display unit 8. The correction method is not limited to the LUT, and other methods such as using a function indicating an input / output relationship may be used.

  Next, for pixels outside the region of interest, the outside region-of-interest gradation correction characteristic determination unit 6 statistically analyzes only the pixel values outside the region of interest (the pixel value of the mask image is “0”), Tone correction characteristics outside the region of interest are determined.

  FIG. 5 is a graph showing an example of the out-of-interest tone correction characteristic created by the out-of-interest tone correction characteristic determination unit 6. In the figure, Xmax and Xmin are called white saturation value and black saturation value, respectively, and are feature amounts calculated from the luminance distribution of the image. The slope a represents the enhancement level and is calculated by the following equation.

a = 100 / (Xmax−Xmin) (3)
The gradation correction characteristic graph is created by a broken line composed of three straight lines. The input luminance value is determined so that the slope in the range from Xmin to Xmax is a, and the slope in the remaining range is 0. Also, the entire polygonal line is created so that it passes through the origin and (100, 100) and increases monotonously. As a result, the contrast at the intermediate luminance level is enhanced, and the greater the value of a, the stronger the enhancement. In the range where the remaining inclination is 0, the gradation change of the output luminance value is suppressed.

  An example of the processing flow of the out-of-focus tone correction characteristic determination unit 6 is shown in FIG. In FIG. 6, first, the out-of-interest gradation correction characteristic determination unit 6 creates a histogram of luminance values of pixels outside the attention area set in the input image (step S11). Next, the white saturation value Xmax is calculated based on the luminance histogram (step S12). For example, the frequency of the histogram is added in order from the highest luminance value, and the maximum luminance value in which the ratio of the total frequency to the number of pixels outside the attention area does not exceed the first threshold specified in advance is saturated with white. Let it be the value Xmax. Then, a black saturation value Xmin is calculated based on the luminance histogram (step S13). For example, the frequency of the histogram is added in order from the lowest luminance value, and the minimum luminance value in which the ratio of the total frequency to the number of pixels outside the attention area does not exceed the second threshold specified in advance is saturated with black. Let it be the value Xmin. FIG. 7 shows the relationship between the luminance histogram, the white saturation value, the black saturation value, the first threshold value, and the second threshold value.

  Next, the inclination a is calculated using the above equation (3) (step S14). Then, the equation of the three straight lines constituting the graph shown in FIG. 5 is calculated (step S15). Finally, a lookup table (LUT) describing the gradation correction characteristics is created and output (step S16).

  In the above example, the gradient in the range where the input luminance value is greater than or equal to Xmax or less than or equal to Xmin is set to 0. However, the gradient is not limited to 0. Further, the gradation correction characteristics are determined based on the black saturation value and the white saturation value, but the present invention is not limited to this example, and other contrast adjustment methods using pixel value statistics may be used. Moreover, although the histogram is used as the statistic of the pixel value, the statistic is not limited to the histogram, and another statistic may be used.

  The out-of-interest tone correction calculation unit 7 performs tone correction on the luminance value of the pixels outside the attention region using the out-of-interest tone correction characteristic determined by the out-of-interest tone correction characteristic determination unit 6. The corrected image is output to the display unit 8.

  Then, the display unit 8 synthesizes the images output from the in-region-in-region gradation correction calculation unit 5 and the out-of-region-in-region gradation correction calculation unit 7, and displays and outputs this combined image. The display unit 8 is composed of, for example, an LCD (Liquid Crystal Display).

  In the above example, the tone correction characteristics represented by the line graph are created in the tone correction characteristics determining section 4 and the tone correction characteristics determining section 6 outside the focus area, but the invention is not limited to the polygonal line. Alternatively, the bent portion of the broken line may be corrected to be curved, or a curved characteristic may be created from the beginning. In the above example, contrast enhancement using a luminance value has been described. However, the present invention is not limited to the luminance value, and other indicators relating to brightness such as brightness may be used.

As described above, according to the image display apparatus of the present embodiment, it is possible to specify an image area and a gradation range for which gradation correction processing is performed, and to perform gradation correction processing independently inside and outside the attention area. Thus, it is possible to accurately highlight and display detailed information that the user wants to pay attention to.
(Second embodiment)
FIG. 8 is a block diagram showing a schematic configuration example of an image display apparatus according to the second embodiment of the present invention. In the figure, 9 indicates an in-region gradation correction characteristic determination unit. The difference from the configuration of FIG. 1 of the first embodiment is that the input image and the mask image are input to the in-region tone correction characteristic determination unit 9. In the present embodiment, not only the central luminance value but also the statistic of the pixel value can be taken into account when determining the in-region tone correction characteristic.

  FIG. 9 is a graph showing an example of the in-region gradation correction characteristic created by the in-region gradation correction characteristic determination unit 9. In the figure, c is a central luminance value, and w is a preset enhanced luminance width. “a” is a preset enhancement level (a> 1), and the gradation correction characteristic is determined so that the slope is “a” in the range of the input luminance value from c−w / 2 to c + w / 2. Thereby, the contrast of the gradation near the central luminance value c is enhanced, and the greater the value of a, the stronger the enhancement. The white saturation value Xmax and the black saturation value Xmin are feature amounts calculated from the luminance distribution of the image. In the range where the input luminance value is greater than or equal to Xmax and the range where Xmin is less than or equal to Xmin, the gradient is set to 0 and the gradation change of the output luminance value is suppressed. In the remaining range on the horizontal axis, the slope is b, and this slope b is calculated using the following equation.

b = (100−wa) / (Xmax−Xmin−w) (4)
In this way, the gradation correction characteristic graph is created as a broken line composed of five straight lines. However, it is necessary to set a and w in a range where b is 0 or more.

  FIG. 10 shows an example of the flow of processing in the in-region gradation correction characteristic determination unit 9. Steps S21 to S23 in this example are the same as those in FIG. 6 showing the flow of the out-of-region gradation correction characteristic determination unit 6 in the first embodiment. In step S24, the slope b is calculated using the above equation (4). Then, an equation of five straight lines constituting the graph shown in FIG. 9 is calculated (step 25). Finally, a look-up table (LUT) describing the tone correction characteristics is created and output (step S26).

  In the above example, the gradient in the range where the input luminance value is greater than or equal to Xmax or less than or equal to Xmin is set to 0. However, the gradient is not limited to 0.

  As described above, according to the image display apparatus of the present embodiment, it is possible to enhance the contrast of the region that the user pays attention to and improve the sense of contrast within the attention region.

(Third embodiment)
FIG. 11 is a block diagram showing a schematic configuration example of an image display device according to the third embodiment of the present invention, in which 10 is an overall tone correction characteristic determining unit, 11 is an overall tone correction calculating unit, Reference numeral 12 denotes a central luminance value determination unit, 13 denotes an in-region tone correction characteristic determination unit, 14 denotes an in-region tone correction calculation unit, and 15 denotes a display unit. This embodiment is different from the first embodiment in that tone correction is performed again only within the attention area after tone correction is performed on the entire image.

  First, the overall tone correction characteristic determination unit 10 creates an overall tone correction characteristic based on the statistic of the pixel value of the entire image. This is performed by calculating the statistic of the pixel value of the entire image by the same method as the out-of-interest gradation correction characteristic determination unit 6 of the first embodiment. The overall tone correction calculation unit 11 performs tone correction based on the overall tone correction characteristics and outputs the result to the display unit 15.

  The central luminance value determination unit 12 determines the central luminance value by the same method as that of the first embodiment, but is calculated from the luminance value of an image that has already been subjected to gradation correction by the overall gradation correction calculation unit 11. Is different.

  The attention area gradation correction characteristic determination unit 13 creates gradation correction characteristics in the attention area by the same method as in the first embodiment. The attention area gradation correction calculation unit 14 performs gradation correction on the attention area of the image that has already been subjected to gradation correction by the same method as in the first embodiment. The display unit 15 replaces the pixels in the attention area of the corrected image output from the overall gradation correction calculation section 11 with the pixel values of the corrected image output from the attention area gradation correction calculation section 14 and displays them. To do.

  As described above, according to the image display apparatus of the present embodiment, it is possible to enhance the contrast of the region that the user pays attention to and improve the sense of contrast within the attention region.

(Fourth embodiment)
FIG. 12 is a block diagram showing a schematic configuration example of an image display apparatus according to the fourth embodiment of the present invention, in which 16 indicates a correction coefficient acquisition unit and 17 indicates an in-region correction characteristic determination unit. In this embodiment, after determining the in-region tone correction characteristic from the central luminance value in the same manner as in the first embodiment, a correction coefficient is further set by user input, and the in-region tone correction characteristic is set. It can be adjusted.

  The correction coefficient acquisition unit 16 acquires a correction coefficient for adjusting a luminance level, which is an example of gradation correction characteristics in the attention area, and outputs the correction coefficient to the attention area correction characteristic determination section 17 in accordance with an input from the user. The in-region correction characteristic determination unit 17 creates the in-region gradation correction characteristic based on the central luminance value and the correction coefficient.

  For example, the correction coefficient acquisition unit 16 acquires a correction coefficient for correcting the enhancement level a used in the first embodiment. The correction coefficient acquisition screen is displayed on the display unit 8, and the user inputs “strong” or “weak” from the screen by operating the touch panel or the remote controller. When these inputs are made, the correction coefficient acquisition unit 16 sets a correction coefficient designated in advance. As the correction coefficient, for example, a value of 1.1 is designated in advance when the input is “strong” and 0.9 is designated when the input is “weak”. The in-region correction characteristic determination unit 17 multiplies a fixed enhancement level a designated in advance by a correction coefficient, and then creates a gradation correction characteristic by the same method as in the first embodiment. As a result, the tone correction characteristics within the attention area are adjusted.

  Here, when the user inputs “strongly” or “weakly” a plurality of times, the correction coefficient may be multiplied a plurality of times according to the number of times. Further, a means for directly inputting the numerical value of the correction coefficient may be provided. Thus, the correction level can be freely adjusted according to the user's intention.

  As another example of the correction coefficient acquisition unit 16, a coefficient for correcting the luminance level may be acquired. Using the same means as in the above example, the user inputs “brighter” or “darker”. When these inputs are made, the correction coefficient acquisition unit 16 sets a correction coefficient designated in advance. For example, a value of +10 is designated in advance when the input is “bright”, and a value of −10 is designated in the case of “dark”. The in-region correction characteristic determination unit 17 adds a correction coefficient to the gradation correction characteristic created by the same method as in the first embodiment. FIG. 13 shows an example of the corrected gradation correction characteristic. Clip processing is performed when the output luminance value exceeds 100% by addition of the correction coefficient, and when it becomes less than 0%, it is clipped.

  As described above, according to the image display device of the present embodiment, when performing gradation correction processing on an image, the user's intention can be taken in and the degree of correction can be adjusted.

(Fifth embodiment)
FIG. 14 is a block diagram showing a schematic configuration example of an image display apparatus according to the fifth embodiment of the present invention, in which 18 is a motion vector detection unit, 19 is a region of interest tracking unit, 20 is a frame memory, 21 Indicates memory. In FIG. 14, the attention area position acquisition unit 1, the image division unit 2, the central luminance value determination unit 3, the attention region gradation correction characteristic determination unit 4, and the attention region outside gradation correction characteristic determination unit 6 are described. It shall be omitted.

  In the fifth embodiment, when the input image is a moving image, a configuration for following the attention area in accordance with the movement of the image is added. The attention area following section 19 follows the attention area set by the image dividing section 2 based on the motion vector between frames of the input image. Here, as described in the first embodiment, the image display apparatus performs gradation correction within the attention area designated by the user and outside the other attention area. At that time, the previous frame image and the previous frame mask image are stored in the frame memory 20 for the next input frame image, and the in-region tone correction characteristics and the out-of-region tone correction characteristics of the previous frame image are stored in the memory. 21 is stored.

  In FIG. 14, for the next input frame image, the motion vector detection unit 18 detects the motion vector of each pixel between the input frame image and the previous frame image. This motion vector can be detected using a known technique such as block matching. Next, the attention area follower 19 creates a mask image in the input frame image from the motion vector obtained by the motion vector detector 18 and the previous frame mask image. This is because the motion vector corresponding to the pixel is added to the coordinates of each pixel whose pixel value is “1” in the previous frame mask image, and the pixel value of the mask image in the input frame image is set to “1” for the obtained coordinates. And the pixel values of the remaining pixels of the mask image of the input frame image are set to “0”. Thus, by providing the attention area follower 19, the attention area can be made to follow the movement of the image.

  Then, the attention area inside gradation correction calculation section 5 and the attention area outside gradation correction calculation section 7 distinguish the inside of the attention area from the outside of the attention area using the mask image created by the attention area tracking section 19, respectively. The gradation correction is performed on the above area in the same manner as in the first embodiment. However, it is desirable to use the values stored in the previous frame image as they are for the in-region tone correction characteristics and the out-of-interest tone correction characteristics. This is to prevent the degree of correction from being changed between frames when the tone correction characteristics are changed, thereby preventing loss of visual smoothness.

  As described above, according to the image display apparatus of the present embodiment, when gradation correction processing is performed on a moving image, the degree of correction can be controlled for each region in accordance with the motion of the image.

  In the above, each embodiment according to the image display apparatus of the present invention has been described, but it goes without saying that the present invention may be configured as an image processing apparatus having no display unit. Further, a form as a program for causing a computer to execute the function as the image processing apparatus or the image display apparatus of the present invention may be used, or a form as a computer-readable recording medium on which the program is recorded.

DESCRIPTION OF SYMBOLS 1 ... Attention area position acquisition part, 2 ... Image division part, 3 ... Center brightness | luminance value determination part, 4 ... Tone area inside tone correction characteristic determination part, 5 ... Attention area inside tone correction calculation part, 6 ... Out of attention area Gradation correction characteristic determination unit, 7 ... Out-of-interest tone correction calculation unit, 8 ... Display unit, 9 ... In-interest region tone correction characteristic determination unit, 10 ... Overall tone correction property determination unit, 11 ... Overall tone Correction characteristic calculation unit, 12... Central luminance value determination unit, 13... In-region gradation correction characteristic determination unit, 14... In-region gradation correction calculation unit, 15 ... Display unit, 16. An attention area gradation correction characteristic determination unit, 18 ... a motion vector detection part, 19 ... an attention area tracking part, 20 ... a frame memory, 21 ... a memory.

Claims (10)

An image processing apparatus that performs gradation correction on an input image,
An attention area setting section that sets an attention area for the input image, a central pixel value acquisition section that acquires a central pixel value of the set attention area, and gradation correction characteristics are determined based on the acquired central pixel value Set in the attention area gradation correction characteristic determination section, the attention area gradation correction calculation section that performs gradation correction in the attention area based on the determined gradation correction characteristics, and the attention area setting section. A pixel value statistic for a pixel outside the attention area is calculated, and a gradation correction characteristic is determined based on the calculated pixel value statistic, and the determined gradation correction An image processing apparatus, comprising: an outside-of-interest-area gradation correction calculating unit that performs gradation correction outside the above-mentioned area based on characteristics.   The image processing apparatus according to claim 1, wherein the in-region tone correction characteristic determination unit calculates a statistic of a pixel value for a pixel in the region of interest set by the region of interest setting unit, and the calculated pixel An image processing apparatus, wherein gradation correction characteristics are determined based on a statistic value and a central pixel value acquired by the central pixel value acquisition unit.   The overall gradation correction characteristic determination according to claim 1, wherein a statistic of a pixel value is calculated for pixels of the entire input image, and a gradation correction characteristic is determined based on the calculated statistic of the pixel value. And an overall tone correction calculation unit that performs tone correction of the entire input image based on the determined tone correction characteristics, and the central pixel value acquisition unit is configured to An image processing apparatus, wherein a central pixel value of an attention area set by the attention area setting unit is acquired for the entire input image subjected to tone correction.   The image processing apparatus according to claim 1, further comprising: a correction coefficient acquisition unit that acquires a correction coefficient for adjusting a gradation correction characteristic in the attention area based on an input by a user, The correction characteristic determination unit determines a gradation correction characteristic based on the central pixel value acquired by the central pixel value acquisition unit and the correction coefficient acquired by the correction coefficient acquisition unit. .   5. The image processing device according to claim 1, wherein the attention area setting section sets the attention area for the input image in accordance with a user operation input. 6. apparatus.   6. The image processing apparatus according to claim 1, wherein the statistic is a luminance histogram.   The image processing device according to claim 1, further comprising an attention area tracking unit that tracks the attention area set by the attention area setting unit based on a motion vector between frames of the input image. The intra-region-of-interest tone correction calculator calculates a tone based on the tone correction characteristic determined by the intra-region-of-interest tone correction characteristic determination unit with respect to the region of interest tracked by the region-of-interest tracking unit. Correction is performed, and the out-of-focus area tone correction calculation unit has the tone correction characteristic determined by the out-of-focus area tone correction characteristic determination unit with respect to the out-of-focus area that is tracked by the focused area tracking unit. An image processing apparatus performing gradation correction based on the image processing apparatus.   The image processing apparatus according to claim 1, wherein the in-region tone correction characteristic determined by the in-region tone correction characteristic determination unit is an input luminance range in which contrast is enhanced. And an input luminance range in which contrast is suppressed, and the central pixel value acquired by the central pixel value acquisition unit is included in the input luminance range in which the contrast is enhanced.   9. The image processing apparatus according to claim 6, wherein the out-of-focus area gradation correction characteristic determination unit sequentially adds the frequencies of the luminance histogram in descending order of luminance value, and totals the sums. The maximum luminance value in which the ratio of the frequency to the number of pixels outside the attention area does not exceed the first threshold value outside the attention area specified in advance is determined as a white saturation value, and the frequency of the luminance histogram is low. The minimum luminance value in which the ratio of the total frequency to the number of pixels outside the region of interest does not exceed the second threshold value outside the region of interest specified in advance is determined as a black saturation value. The image processing apparatus is characterized in that the tone correction characteristic is a characteristic that enhances contrast in a range where an input luminance value is not less than the black saturation value and not more than the white saturation value.   An image display device comprising: the image processing device according to claim 1; and a display unit that displays an input image.

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