JP6857102B2 - Image processing equipment, image processing methods, and programs - Google Patents

Description

The present invention relates to an image processing apparatus, an image processing method, and a program.

When a high-brightness subject or a high-saturation subject is photographed by the image pickup device, any of the RGB signals output from the image pickup sensor may become saturated. In this case, the ratio of the RGB signals changes from the value representing the original color of the subject, so that color bending occurs.

To solve this problem, by applying a color suppression process, which is a process for reducing the saturation, to a region where any of the RGB signals is saturated in the past, the color bending caused by the saturation of the signal is alleviated. The technology is known.

Further, when a low-luminance and high-saturation subject is photographed by the imaging device, one of the RGB signals may approach the black level, which is the lower limit. In this case, when gamma correction with a steep rise at the black level is applied to the RGB signal, the noise component superimposed on the RGB signal is emphasized by the gamma correction, causing deterioration in image quality.

To solve this problem, conventionally, a technique for raising the signal level of a signal having a small signal value among RGB signals by applying color suppression processing to a lower limit region in which any of the RGB signals takes a value close to the lower limit. It has been known. As a result, the degree of emphasis of the noise component due to gamma correction can be reduced.

For example, Patent Document 1 discloses a technique for performing color suppression processing based on the maximum value or the minimum value of an RGB signal so that the value falls within a predetermined reference range.

Japanese Unexamined Patent Publication No. 7-288837

According to Patent Document 1, the correction coefficient for the color suppression process changes according to the value of the luminance signal. Even if the maximum value, the intermediate value, and the minimum value match between the two sets of RGB signals, the luminance signals are different if the colors corresponding to the maximum value, the intermediate value, and the minimum value are different. For example, when the RGB signal value is expressed in the range of 0 to 1 and yellow (R = G = 1, B = 0) and magenta (R = B = 1, G = 0) are considered, these two colors The maximum, intermediate, and minimum values match (maximum value = intermediate value = 1, minimum value = 0), but the luminance signals are different. Therefore, in the technique of Patent Document 1, it is not easy to design the correspondence between the signal value of the RGB signal and the correction coefficient as desired.

The present invention has been made in view of such a situation, and provides a technique capable of easily adjusting the intensity of the color suppression treatment.

In order to solve the above problems, the present invention includes a first one or more components that do not include the minimum value component of the RGB components and the first one or more components from the RGB components of the image signal. A selection means for selecting different second one or more components, a determination means for determining whether or not the size of the first one or more component is equal to or greater than a threshold level, and the second one or more. A determination means for determining the intensity of the color suppression treatment based on the components of the above, and when the size of the first one or more components is equal to or greater than the threshold level, the determined intensity is used with respect to the image signal. Provided is an image processing apparatus including an image processing means for performing color suppression processing.

Other features of the present invention will be further clarified by the accompanying drawings and the description in the form for carrying out the following invention.

According to the present invention, the intensity of the color suppression treatment can be easily adjusted.

The block diagram which shows the structure of a digital camera 100. The figure which shows the functional block which concerns on the color suppression processing of the image processing unit 105 which concerns on 1st Embodiment. The flowchart which shows the flow of the color suppression processing in the image processing unit 105 which concerns on 1st Embodiment. The figure explaining the method of calculating the value of L. The figure which shows the functional block which concerns on the color suppression processing of the image processing unit 105 which concerns on 2nd Embodiment. A flowchart showing the flow of color suppression processing in the image processing unit 105 according to the second embodiment. The figure explaining the method of calculating the value of N.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The technical scope of the present invention is determined by the scope of claims, and is not limited by the following individual embodiments. Also, not all combinations of features described in the embodiments are essential to the present invention. It is also possible to appropriately combine the features described in the separate embodiments.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a digital camera 100 which is an example of an image processing device. In FIG. 1, the lens group 101 is a zoom lens including a focus lens. A shutter 102 having an aperture function is provided between the lens group 101 and the imaging unit 103. The image pickup unit 103 has an image pickup element typified by a CCD / CMOS image sensor that converts an optical image formed on the image pickup surface by the lens group 101 into an electric signal for each pixel. The A / D converter 104 converts the analog signal output by the imaging unit 103 into a digital signal (image data).

The image processing unit 105 performs various image processing such as color interpolation (demosaic), white balance adjustment, and γ correction on the image data output from the A / D converter 104. The image processing unit 105 also performs color suppression processing on the saturated region of the color signal. The image memory 106 temporarily stores image data. The memory control unit 107 controls reading and writing of the image memory 106. The D / A converter 108 converts the image data into an analog signal. The display unit 109 has a display device such as an LCD or an organic EL display, and displays various GUIs, live view images, images read and reproduced from the recording medium 112, and the like. The codec unit 110 encodes the image data stored in the image memory 106 by a predetermined method for recording on the recording medium 112, or decodes the coded image data included in the image file for display, for example. To do.

The I / F 111 (interface) mechanically and electrically connects a removable recording medium 112 such as a semiconductor memory card or a card-type hard disk to the digital camera 100. The system control unit 50 may be a programmable processor such as a CPU or MPU. The system control unit 50 realizes the functions of the digital camera 100 by, for example, executing a program recorded in the non-volatile memory 121 or the built-in non-volatile memory to control necessary blocks and circuits.

The operation unit 120 collectively describes input devices such as buttons and switches for the user to input various instructions to the digital camera 100. When the display unit 109 is a touch display, the touch panel is included in the operation unit 120. Further, the operation unit 120 may include an input device of a type such as voice input or line-of-sight input that inputs an instruction without contact.

The non-volatile memory 121 may be, for example, an EEPROM that can be electrically erased and recorded. The non-volatile memory 121 records various set values, GUI data, and a program for execution by the system control unit 50 when the system control unit 50 is an MPU or a CPU. The system memory 122 is used to develop constants, variables, programs read from the non-volatile memory 121, etc. for the operation of the system control unit 50.

Next, the basic operation at the time of shooting a subject with the digital camera 100 configured as described above will be described. The image pickup unit 103 photoelectrically converts the subject image formed on the image pickup surface by the lens group 101 when the shutter 102 is open by the image pickup element, and outputs the analog image signal to the A / D converter 104. The A / D converter 104 converts the analog image signal output from the image pickup unit 103 into a digital image signal (image data) and outputs the analog image signal to the image processing unit 105.

The image processing unit 105 performs various image processing such as simultaneous processing (demosaic processing), color suppression processing, and γ correction on the image data from the A / D converter 104 or the image data from the memory control unit 107. Do. In addition, the image processing unit 105 performs predetermined arithmetic processing related to brightness, contrast, etc. using the image data obtained by shooting, and the system control unit 50 performs focus adjustment (AF) and exposure based on the obtained arithmetic results. Control (AE) is performed.

The image data output from the image processing unit 105 is written to the image memory 106 via the memory control unit 107. The image memory 106 stores the image data output from the imaging unit 103 and the image data to be displayed on the display unit 109.

The D / A converter 108 converts the image display data stored in the image memory 106 into an analog signal and supplies it to the display unit 109. The display unit 109 displays on a display device such as an LCD according to the analog signal from the D / A converter 108.

The codec unit 110 encodes the image data recorded in the image memory 106 based on a standard such as JPEG or MPEG. The system control unit 50 adds a predetermined header or the like to the encoded image data to form an image file, and records the encoded image data on the recording medium 112 via the I / F 111.

Further, the digital camera 100 can make the display unit 109 function as an electronic viewfinder (EVF) by shooting a moving image in the shooting standby state and continuously displaying the shot moving image on the display unit 109. In this case, the digital camera 100 keeps the shutter 102 open and uses the so-called electronic shutter of the imaging unit 103 to take a picture at, for example, 30 frames / second. Then, when the shutter button included in the operation unit 120 is half-pressed, the above-mentioned AF and AE control is performed, and when the shutter button is fully pressed, still image shooting for recording is executed by the main shooting and recorded on the recording medium 112. To. Further, when the moving image shooting is instructed by the moving image shooting button or the like, the digital camera 100 starts recording the moving image on the recording medium 112.

As described above, the digital camera 100 is an example of an image processing device, and a configuration related to shooting and recording is not essential.

FIG. 2 is a diagram showing a functional block related to color suppression processing of the image processing unit 105. It should be noted that one or more of the functional blocks shown in FIG. 2 may be realized by a combination of a microprocessor and software. Alternatively, one or more of the functional blocks shown in FIG. 2 may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or a PLD (Programmable Logic Device). The PLD includes an FPGA (Field-Programmable Gate Array), a PLA (Programmable Logic Array), and the like.

The configuration of the image processing unit 105 and the flow of the processing when the color suppression processing is performed will be described. In FIG. 2, 201 is an image signal generation unit, 202 is an image signal conversion unit, 203 is a color suppression processing unit, 204 is an image signal inverse conversion unit, and 205 is a color suppression characteristic control unit. The color suppression characteristic control unit 205 includes a Max-Med-Min determination unit 211, a color signal saturation determination unit 212, and a color suppression gain calculation unit 213.

Next, the flow of the color suppression process in the image processing unit 105 will be described with reference to FIG. FIG. 3 is a flowchart showing the flow of color suppression processing in the image processing unit 105. In S301, the image signal generation unit 201 performs simultaneous processing (demosaic processing) on an image signal having information of one color (any one of R, G, and B) per pixel, and each pixel has three colors (RGB). ) Is generated as an image signal. The image signal generation unit 201 outputs the generated image signal to the image signal conversion unit 202 and the Max-Med-Min determination unit 211.

The processing after S302 is performed on a pixel-by-pixel basis. In S302, the Max-Med-Min determination unit 211 determines the magnitude relationship between the input R, G, and B signal values (RGB components of the image signal), and the Max signal (maximum value component) and Med signal in descending order. Judgment is made as (intermediate value component) and Min signal (minimum value component). The Max-Med-Min determination unit 211 outputs the Max signal value to the color signal saturation determination unit 212, and outputs the Max signal, Med signal, and Min signal values to the color suppression gain calculation unit 213.

In S303, the color signal saturation determination unit 212 compares the value of the input Max signal with a predetermined threshold value (TH_MAX), and determines whether or not the input image signal is saturated. The color signal saturation determination unit 212 determines that the image signal is saturated when Max ≧ TH_MAX, and determines that the image signal is not saturated otherwise. If the image signal is saturated, the process proceeds to S304, and if the image signal is not saturated, the process proceeds to S305.

The threshold value (TH_MAX) may be a predetermined constant, or may be determined according to the value of the Min signal or the Med signal based on the predetermined reference value. For example, when the Min signal or Med signal is small, the threshold value (TH_MAX) value may be set small. This makes it possible to adjust the intensity of the color suppression processing in a region where the Min signal and the Med signal are small and the saturation is high.

In S304, the color suppression gain calculation unit 213 calculates the color suppression gain (gain) based on the input Max signal, Med signal, and Min signal values. Details of the method for calculating the color suppression gain will be described later.

In S305, the color suppression gain calculation unit 213 determines the color suppression gain (gain) to 1.

In S306, color suppression processing is performed on the image signal based on the value of the color suppression gain (gain) obtained in S304 or S305. Specifically, the image signal conversion unit 202 converts the input RGB signal into a YUV signal. Then, the color suppression processing unit 203 applies a color suppression gain (gain) to the U and V signals based on the following equation.
Uout = U × gain
Vout = V × gain

The color suppression processing unit 203 outputs the luminance signal Y and the color difference signals Out and Vout to which the color suppression gain is applied to the image signal inverse conversion unit 204. The image signal inverse conversion unit 204 converts the input YUV signal into an RGB signal. After that, the image correction unit (not shown) of the image processing unit 105 performs correction processing of the image signal such as gamma correction.

Next, a method of calculating the color suppression gain (gain) in S304 will be described. The formula for calculating the color suppression gain (gain) is as follows.
gain_max = K × L
gain = 1-gain_max = 1-K × L
However, K and L are values calculated based on the values of Max, Med, and Min, and the calculation method thereof will be described later. As shown in the equation, as the values of K and L increase, the value of gain approaches zero and the intensity of the color suppression treatment becomes stronger.

Here, K is a value representing the degree of saturation of the color signal, and is calculated based on the following calculation formula. The Max, Med, and Min values (that is, RGB values) are represented in the range of 0 to 1.
K = Max-TH_MAX

Next, a method of calculating the value of L will be described with reference to FIGS. 4A to 4B. Figures 4 (A) to 4 (B) are examples of reference tables for determining the value of L, respectively, and exemplify two methods for determining the reference value.

First, a case where the reference table shown in FIG. 4A is used will be described. The horizontal axis of FIG. 4A represents a value of α × Min + (1-α) × Med, and α is a ratio coefficient set by a value between 0 and 1. The vertical axis of FIG. 4A is the value of L. When the Med and Min values are input, the color suppression gain calculation unit 213 calculates the value of α × Min + (1-α) × Med, and uses the value and the reference table shown in FIG. 4 (A). The value of L is determined based on this.

The input / output characteristics of the reference table shown in FIG. 4A are defined so that the larger the Min and Med values, the larger the L value. Therefore, the finally calculated gain value has a characteristic that the larger the Min and Med values, the closer to 0 the value is. By doing so, it is possible to apply the color suppression process to the saturated region and control the color suppression characteristic so that the saturation gradually decreases as the signal level increases and approaches white.

Further, by adjusting the value of the ratio coefficient α, the color suppression characteristic can be controlled more finely. For example, when the value of α is brought close to 1, the value of L becomes large only in the region where the value of Min is large, so that the region where the color suppression is strongly applied is narrowed.

The color suppression gain calculation unit 213 outputs the calculated gain value to the color suppression processing unit 203.

Next, a case where the reference table shown in FIG. 4B is used will be described. The horizontal axis of FIG. 4B represents the value of Min, and P1 and P2 are predetermined threshold values. The vertical axis of FIG. 4B is the value of L. As shown in FIG. 4B, the reference table is defined so that the larger the Min value, the smaller the L value. As a result, in the region where the Min value is small, it is possible to control so as to increase the intensity of the color suppression treatment. By doing so, it is possible to reduce image quality deterioration (enhancement of noise components) that occurs when gamma correction is applied to a color signal having a small Min value.

As described above, the digital camera 100 has Max (maximum value component), Med (intermediate value component), and Min (minimum value component) depending on the magnitude relation of each color of the input RGB signal (each of the RGB components of the image signal). Determine the value. Then, the digital camera 100 determines the color suppression characteristic (intensity of the color suppression processing) based on the values of Max (maximum value component), Med (intermediate value component), and Min (minimum value component). At that time, the digital camera 100 controls so that the values of Med and Min increase with respect to the region where Max is equal to or higher than a predetermined threshold value, and the value of the color suppression gain decreases as the saturation level approaches (FIG. FIG. 4 (A)). As a result, when applying the color suppression gain to the saturation region of the RGB signal, it is possible to perform the color suppression processing by the gain characteristic without discontinuity. Further, since the color suppression processing is controlled based on the signal level of the RGB signal, the intensity of the color suppression processing is controlled to be the same in the region where the signal level of the RGB signal is the same regardless of the hue of the target region. can do.

In the above description, the reference table is used when determining the color suppression characteristics based on the values of Med and Min, but in the present embodiment, the method for determining the color suppression characteristics is limited to this. is not it. For example, the color suppression characteristic may be determined by calculating a predetermined mathematical formula using the values of Med and Min. In this case, as with the characteristics of the reference table, the characteristics of a predetermined mathematical expression may be determined so that the larger the Med and Min values, the smaller the value of the color suppression gain.

Further, in the above description, the Max value is also used when calculating the color suppression gain, but the present embodiment does not limit the calculation method of the color suppression gain to this. For example, the Max value may be used only for determining the saturation region, and the color suppression gain may be determined based on the Med and Min values. Further, the color suppression gain may be determined based on only one of Med and Min.

Further, in the above description, the Max value is used when determining the saturation of the RGB signal, but the present embodiment is not limited to the method of determining the saturation of the RGB signal. For example, among the RGB signals, a signal having a value equal to or higher than a threshold value may be selected, and the presence or absence of saturation of the color signal may be determined based on the average value. However, at least the Min value is not used for the saturation determination.

Generally speaking, the digital camera 100 selects one or more components (first one or more components) that do not include the minimum value component (Min) of the RGB components from the RGB components of the image signal for saturation determination. Select as an ingredient. The digital camera 100 determines whether or not the magnitude of the first one or more components is equal to or greater than the threshold level. For example, when the first 1 or more component is Max (maximum value component), the digital camera 100 states that if Max is equal to or more than the threshold value, the size of the first 1 or more component is equal to or more than the threshold level. judge. Alternatively, for example, when the first one or more components are Max (maximum value component) and Med (intermediate value component), the digital camera 100 is the first if the average value of Max and Med is equal to or more than the threshold value. It is determined that the magnitude of one or more components is equal to or greater than the threshold level. Further, the digital camera 100 uses one or more components (second one or more components) different from the first one or more components as components for determining the intensity of the color suppression process from the RGB components of the image signal. select. The digital camera 100 determines the intensity of the color suppression process based on the second one or more components. For example, when the second one or more components are Med (intermediate value component) and Min (minimum value component), the digital camera 100 performs color suppression processing based on the value obtained by adding Med and Min by the ratio α. Determine the strength. Alternatively, for example, when the second one or more components are Min (minimum value component), the digital camera 100 determines the intensity of the color suppression process based on the Min value. In addition, in the digital camera 100, in addition to one or more components (second one or more components) different from the first one or more components, the intensity of the color suppression treatment is determined based on the first one or more components. It may be determined (see S304 in FIG. 3).

Further, in the above description, when calculating the color suppression gain, a value obtained by adding Med and Min at a predetermined ratio α is used (in the case of FIG. 4A). However, if it is desired to finely adjust the characteristics of the color suppression process according to the hue, the value of α may be controlled so as to be determined according to at least one of the hue component and the saturation component of the input image signal. For example, when the hue of the input image signal is a complementary color (yellow, cyan, magenta), the value of α is set larger than when it is a primary color (red, blue, green). By doing so, the same color suppression effect can be given to both the hue (complementary color) in which Med takes a relatively large value and the hue (primary color) in which Med takes a small value. It becomes possible to control.

Further, in the above description, it is controlled so that the intensity of the color suppression treatment becomes stronger as the values of Med and Min increase (in the case of FIG. 4A), but in the present embodiment, the color suppression characteristics are controlled. The determination method is not limited to this. Any method may be used as long as it is a method using the values of Med and Min and has a characteristic that the color suppression characteristic continuously changes according to the signal level. For example, when the values of Med and Min are equal to or less than a predetermined threshold value, the color suppression process may be controlled to be strengthened. By doing so, the intensity of the color suppression processing in the region where the Med and Min values are small and the Max value is large (that is, the region with high saturation) is strengthened, and the balance of color reproduction in the entire image is balanced. It becomes possible to adjust.

As described above, according to the first embodiment, the digital camera 100 includes the first one or more components that do not include the minimum value component of the RGB components from the RGB components of the image signal, and the first one. A second or more component that is different from the one or more component is selected. Then, the digital camera 100 makes a saturation determination based on the first one or more components, and determines the intensity of the color suppression process based on the second one or more components. This makes it possible to easily adjust the intensity of the color suppression treatment.

[Second Embodiment]
In the first embodiment, the configuration in which the color suppression processing for the saturated region is performed with reference to the Max value of the RGB signal has been described. In the second embodiment, a configuration in which the color suppression process for the lower limit region is performed with reference to the Min value of the RGB signal will be described. Here, the lower limit region refers to a region in the color space in which any one of the RGB signals has a value close to the lower limit value that the RGB signal can take in the color region.

In the second embodiment, the configuration of the digital camera 100 is the same as that of the first embodiment (see FIG. 1), but the configuration of the image processing unit 105 is different from that of the first embodiment. Hereinafter, parts different from the first embodiment will be mainly described.

FIG. 5 is a diagram showing functional blocks related to color suppression processing of the image processing unit 105. In FIG. 5, blocks having the same or similar functions as those in FIG. 2 are designated by the same reference numerals as those in FIG. It should be noted that one or more of the functional blocks shown in FIG. 5 may be realized by a combination of a microprocessor and software. Alternatively, one or more of the functional blocks shown in FIG. 5 may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or a PLD (Programmable Logic Device). The PLD includes an FPGA (Field-Programmable Gate Array), a PLA (Programmable Logic Array), and the like.

The color suppression characteristic control unit 505 includes a Max-Med-Min determination unit 511, a color signal lower limit determination unit 512, and a color suppression gain calculation unit 513. The Max-Med-Min determination unit 511 determines the magnitude relationship of the input RGB signals, and outputs the minimum value (Min value) of them to the color signal lower limit determination unit 512. Further, the color signal lower limit determination unit 512 uses the input Min signal to determine whether or not the input image signal is included in the lower limit region.

Next, the flow of the color suppression process in the image processing unit 105 will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of color suppression processing in the image processing unit 105. In FIG. 6, the steps in which the same or similar processing as in FIG. 3 is performed are designated by the same reference numerals as those in FIG.

Similar to the first embodiment, the processing after S602 is performed on a pixel-by-pixel basis. In S602, the Max-Med-Min determination unit 511 determines the magnitude relationship between the input R, G, and B signal values (RGB components of the image signal), and determines the magnitude relationship between the Max signal (maximum value component) and the Med signal in descending order. Judgment is made as (intermediate value component) and Min signal (minimum value component). The Max-Med-Min determination unit 511 outputs the Min signal value to the color signal lower limit determination unit 512, and outputs the Max signal, Med signal, and Min signal values to the color suppression gain calculation unit 513.

In S603, the color signal lower limit determination unit 512 compares the value of the input Min signal with a predetermined threshold value (TH_MIN), and determines whether or not the input image signal is included in the lower limit region. The color signal lower limit determination unit 512 determines that the image signal is included in the lower limit region when Min <TH_MIN, and determines that the image signal is not included in the lower limit region otherwise. If the image signal is included in the lower limit region, the process proceeds to S604, and if the image signal is not included in the lower limit region, the process proceeds to S305.

In S604, the color suppression gain calculation unit 513 calculates the color suppression gain (gain) based on the input Max signal, Med signal, and Min signal values. The formula for calculating the color suppression gain (gain) in this embodiment is as follows.
gain_min = M × N
gain = 1-gain_min = 1-M × N
However, M and N are values calculated based on the values of Max, Med, and Min, and the calculation method thereof will be described later. As shown in the equation, the larger the value of M and N, the closer the value of gain approaches zero, and the stronger the intensity of the color suppression treatment.

Here, M is a value representing the degree to which the color signal approaches the lower limit of the signal level, and is calculated based on the following calculation formula.
M = TH_MIN-Min

Next, a method of calculating the value of N will be described with reference to FIG. 7. The horizontal axis of FIG. 7 represents the value of α × Max + (1-α) × Med, and α is a ratio coefficient set by a value between 0 and 1. The vertical axis of FIG. 7 is the value of N. When the Med and Max values are input, the color suppression gain calculation unit 513 calculates the value of α × Max + (1-α) × Med, and N based on the value and the reference table shown in FIG. Determine the value of. The color suppression gain calculation unit 513 outputs the calculated gain value to the color suppression processing unit 203.

As described above, the digital camera 100 has Max (maximum value component), Med (intermediate value component), and Min (minimum value component) depending on the magnitude relation of each color of the input RGB signal (each of the RGB components of the image signal). Determine the value. Then, the digital camera 100 determines the color suppression characteristic (intensity of the color suppression processing) based on the values of Max (maximum value component), Med (intermediate value component), and Min (minimum value component). At that time, the digital camera 100 controls so that the larger the Max and Med values are, the smaller the color suppression gain value is in the region where Min is less than a predetermined threshold value (in the case of FIG. 7). As a result, when applying the color suppression gain to the lower limit region of the color gamut, it is possible to perform the color suppression processing by the gain characteristic without discontinuity. Further, since the color suppression processing is controlled based on the signal level of the RGB signal, the intensity of the color suppression processing is controlled to be the same in the region where the signal level of the RGB signal is the same regardless of the hue of the target region. can do. Further, by performing the color suppression processing on the lower limit region of the color gamut, the Min value becomes large, and as a result, it becomes possible to reduce the deterioration of the image quality (emphasis of the noise component) due to the gamma correction.

In the above description, the configuration in which only the color suppression processing for the color signal is performed has been described, but the correction processing (luminance correction) for the luminance signal may also be performed based on the color suppression characteristics determined according to the above description. Good. Specifically, when the value of the color suppression gain with respect to the lower limit region is small (color suppression processing is performed), the luminance signal is corrected so as to raise the signal level of the luminance signal. The digital camera 100 corrects the luminance component so that the stronger the intensity of the color suppression process, the larger the value of the luminance component. By doing so, since the signal level of the Min value is also corrected to be high, it is possible to reduce the deterioration of the image quality (emphasis of the noise component) due to the gamma correction.

Further, when the image processing unit 105 also performs correction processing on the luminance signal, the color suppression processing is controlled by using information on the characteristics of the luminance signal correction processing in addition to the signal level of the RGB signal. May be good. Specifically, the digital camera 100 calculates the color suppression gain by the method described above. After that, the digital camera 100 refers to the characteristic information of the correction processing for the luminance signal, and the larger the amount (decrease amount) of lowering the signal level of the luminance signal, the smaller the calculated color suppression gain (color suppression processing). Control to strengthen). By doing so, it is possible to reduce image quality deterioration (enhancement of noise components) caused by gamma correction when the signal level of the Min value approaches the lower limit value due to the correction of the luminance signal.

Further, in the above description, the Min value is used when determining whether or not the region is the lower limit region, but the present embodiment does not limit the determination method to this. For example, among the RGB signals, a signal having a value less than the threshold value may be selected, and it may be determined whether or not the color signal is included in the lower limit region based on the average value. However, at least the Max value is not used for determining the lower limit region.

The second embodiment can be generalized in the same way as the first embodiment. That is, the digital camera 100 selects one or more components (first one or more components) that do not include the maximum value component (Max) of the RGB components from the RGB components of the image signal for determining the lower limit region. Select as. The digital camera 100 determines whether or not the magnitude of the first one or more components is less than the threshold level. For example, when the first one or more components are Min (minimum value component), the digital camera 100 states that if Min is less than the threshold value, the magnitude of the first one or more components is less than the threshold level. judge. Alternatively, for example, when the first one or more components are Min (minimum value component) and Med (intermediate value component), the digital camera 100 is the first if the average value of Min and Med is less than the threshold value. It is determined that the magnitude of one or more components is less than the threshold level. Further, the digital camera 100 uses one or more components (second one or more components) different from the first one or more components as components for determining the intensity of the color suppression process from the RGB components of the image signal. select. The digital camera 100 determines the intensity of the color suppression process based on the second one or more components. For example, when the second one or more components are Med (intermediate value component) and Max (maximum value component), the digital camera 100 performs color suppression processing based on the value obtained by adding Med and Max by the ratio α. Determine the strength. Alternatively, for example, when the second one or more components are Max (maximum value component), the digital camera 100 determines the intensity of the color suppression process based on the Max value. In addition, in the digital camera 100, in addition to one or more components (second one or more components) different from the first one or more components, the intensity of the color suppression treatment is determined based on the first one or more components. It may be determined (see S604 in FIG. 6).

As described above, according to the second embodiment, the digital camera 100 includes the first one or more components that do not include the maximum value component of the RGB components from the RGB components of the image signal, and the first one. A second or more component that is different from the one or more component is selected. Then, the digital camera 100 determines the lower limit region based on the first one or more components, and determines the intensity of the color suppression process based on the second one or more components. This makes it possible to easily adjust the intensity of the color suppression treatment.

[Third Embodiment]
In the third embodiment, a configuration in which the saturation determination according to the first embodiment and the lower limit region determination according to the second embodiment are combined will be described. In the second embodiment, the configuration of the digital camera 100 is the same as that of the first embodiment and the second embodiment (see FIG. 1). The image processing unit 105 includes a color suppression characteristic control unit 205 (FIG. 2) and a color suppression characteristic control unit 505 (FIG. 5). Hereinafter, parts different from the first embodiment and the second embodiment will be mainly described.

The image processing unit 105 is configured to combine and use the color suppression gain values calculated by the color suppression gain calculation unit 213 and the color suppression gain calculation unit 513. Specifically, the following processing is performed.

First, the color suppression gain calculation unit 213 calculates the color suppression gain (gain_max) for the saturation region of the RGB signal by the method described in the first embodiment.
gain_max = K × L
However, when Max <TH_MAX (in the case of the unsaturated region), gain_max = 0.

Next, the color suppression gain calculation unit 513 calculates the color suppression gain (gain_min) for the lower limit region of the RGB signal by the method described in the second embodiment.
gain_min = M × N
However, when Min ≧ TH_MIN (in the case of the non-lower limit region), gain_min = 0.

Next, the image processing unit 105 synthesizes each color suppression gain (gain_max, gain_min) according to the following formula, outputs the combined color suppression gain (gain) to the color suppression processing unit 203, and outputs the color for the color difference signal. Perform suppression processing.
gain = 1- (gain_max + gain_min)

As described above, according to the third embodiment, the digital camera 100 applies the color suppression process to both the saturation region and the lower limit region of the input RGB signal. This makes it possible to reduce both the color bending due to saturation and the emphasis of the noise component in the lower limit region.

In the above description, the configuration in which the color suppression gains for the saturation region and the lower limit region of the RGB signal are calculated independently and then added to each other has been described, but in the present embodiment, the calculation method of the color suppression gain is applied to this. It is not limited. For example, in a state where the determination threshold value is set so that the saturation region or the region determined as the lower limit region does not overlap with each other, either the saturation region or the color suppression gain for the lower limit region is calculated according to the RGB signal value. , May be controlled to be used for color suppression processing.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It is also possible to realize the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

50 ... System control unit, 100 ... Digital camera, 105 ... Image processing unit, 202 ... Image signal conversion unit, 203 ... Color suppression processing unit, 205 ... Color suppression characteristic control unit, 211 ... Max-Med-Min determination unit, 212 ... Color signal saturation determination unit, 213 ... Color suppression gain calculation unit

Claims (24)

From the RGB components of the image signal, a first one or more components that do not include the minimum value component of the RGB components and a second one or more components that are different from the first one or more components are selected. How to choose and
A determination means for determining whether or not the size of the first one or more components is equal to or greater than a threshold level, and
A determining means for determining the intensity of the color suppression treatment based on the second one or more components, and
An image processing means that performs color suppression processing on the image signal with the determined intensity when the magnitude of the first one or more components is equal to or greater than the threshold level.
An image processing device comprising. The image processing apparatus according to claim 1, wherein the selection means selects the maximum value component of the RGB components as the first one or more components. The determination means is characterized in that when the value of the maximum value component is equal to or greater than the first threshold value, the determination means determines that the size of the first one or more component is equal to or greater than the threshold level. 2. The image processing apparatus according to 2. The image processing apparatus according to claim 2 or 3, wherein the selection means selects an intermediate value component and the minimum value component of the RGB components as the second or more components. The image processing according to claim 4, wherein the determination means determines the intensity of the color suppression treatment based on a value obtained by adding the minimum value component and the intermediate value component at the first ratio. apparatus. The image processing apparatus according to claim 5, wherein the determination means determines the first ratio based on at least one of a hue component and a saturation component of the image signal. The determination means according to claim 5 or 6, wherein the larger the value obtained by adding the minimum value component and the intermediate value component at the first ratio, the stronger the intensity of the color suppression treatment. The image processing apparatus described. The selection means selects, as the first one or more components, a component having a value equal to or higher than a second threshold value among the RGB components excluding the minimum value component.
When the average value of the first one or more components is equal to or greater than the first threshold value, the determination means determines that the size of the first one or more components is equal to or greater than the threshold level. The image processing apparatus according to claim 1. The image processing according to any one of claims 1 to 3 and 8, wherein the selection means selects the minimum value component of the RGB components as the second or more components. apparatus. The determination means makes the intensity of the color suppression treatment stronger when the value of the minimum value component is equal to or less than the third threshold value than when the value of the minimum value component is larger than the third threshold value. The image processing apparatus according to claim 9. The image processing apparatus according to any one of claims 1 to 10, wherein the determination means determines the threshold level based on the second or more components. From the RGB components of the image signal, a first one or more components that do not include the maximum value component of the RGB components and a second one or more components that are different from the first one or more components are selected. How to choose and
A determination means for determining whether or not the size of the first one or more components is less than the threshold level, and
A determining means for determining the intensity of the color suppression treatment based on the second one or more components, and
An image processing means that performs color suppression processing on the image signal with the determined intensity when the magnitude of the first one or more components is less than the threshold level.
An image processing device comprising. The image processing apparatus according to claim 12, wherein the selection means selects the minimum value component of the RGB components as the first one or more components. The determination means is characterized in that, when the value of the minimum value component is less than the first threshold value, it is determined that the size of the first one or more components is less than the threshold level. 13. The image processing apparatus according to 13. The image processing apparatus according to claim 13, wherein the selection means selects an intermediate value component and the maximum value component of the RGB components as the second or more components. The image processing according to claim 15, wherein the determination means determines the intensity of the color suppression treatment based on a value obtained by adding the maximum value component and the intermediate value component at a first ratio. apparatus. 16. The determination means according to claim 16, wherein the larger the value obtained by adding the maximum value component and the intermediate value component at the first ratio, the stronger the intensity of the color suppression treatment. Image processing device. The selection means selects, as the first one or more components, a component having a value less than the second threshold value among the RGB components excluding the maximum value component.
When the average value of the first one or more components is less than the first threshold value, the determination means determines that the size of the first one or more components is less than the threshold level. The image processing apparatus according to claim 12. The image processing according to any one of claims 12 to 14 and 18, wherein the selection means selects the maximum value component of the RGB components as the second or more components. apparatus. When the magnitude of the first one or more components is less than the threshold level, the brightness that corrects the brightness component so that the stronger the determined intensity is, the larger the value of the brightness component of the image signal is. The image processing apparatus according to any one of claims 12 to 19, further comprising a correction means. Further provided with a luminance correction means for correcting the luminance component of the image signal,
The determination means according to any one of claims 12 to 19, wherein the greater the amount of decrease in the value of the luminance component due to the correction of the luminance component, the stronger the intensity of the color suppression treatment. Image processing equipment. An image processing method executed by an image processing device.
From the RGB components of the image signal, a first one or more components that do not include the minimum value component of the RGB components and a second one or more components that are different from the first one or more components are selected. The selection process to be done and
A determination step for determining whether or not the size of the first one or more components is equal to or greater than the threshold level, and
A determination step of determining the intensity of the color suppression treatment based on the second one or more components, and
An image processing step of performing color suppression processing on the image signal with the determined intensity when the magnitude of the first one or more components is equal to or more than the threshold level.
An image processing method comprising. An image processing method executed by an image processing device.
From the RGB components of the image signal, a first one or more components that do not include the maximum value component of the RGB components and a second one or more components that are different from the first one or more components are selected. The selection process to be done and
A determination step for determining whether or not the size of the first one or more components is less than the threshold level, and
A determination step of determining the intensity of the color suppression treatment based on the second one or more components, and
An image processing step of performing color suppression processing on the image signal with the determined intensity when the magnitude of the first one or more components is less than the threshold level.
An image processing method comprising. A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 21.

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