JP2006148605A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus and an image processing method whereby a display image in response to an original video signal is obtained without incurring decrease in the number of represented colors and the gradation. <P>SOLUTION: The image processing apparatus includes: a first conversion circuit 12 for converting a color space of an input video signal including positive and negative color values from the YCbCr color space into the RGB color space including positive and negative color values; a first correction circuit 13 for carrying out gamma correction in response to a display device with which the input video signal is compatible; and a second conversion circuit 14 for converting the color space into the RGB color space compatible with a color gamut of the display device for displaying the video signal by signal processing reflecting the positive and negative color values and outputting a converted video signal including only the positive color value. When the video signal after the conversion includes the negative color value, the second conversion circuit 14 detects a minimum component whose absolute value is maximum among a plurality of RGB components of the video signal and summates a proportionally adjusted value to each component of the video signal after the conversion on the basis of the minimum component detected from the positive value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an image processing method for performing a color space conversion process on a video signal to be displayed on a display device such as an LCD or a PDP.

  In recent years, development of thin display devices such as LCDs and PDPs has been remarkable as display devices in which CRT has been the mainstream, and video equipment such as televisions employing these display devices have been put into practical use.

In an image display device using these display devices and requiring color reproduction faithful to the video standard, the video signal (video signal) is color space converted to match the display device. Configured to display.
In this type of image processing apparatus, for example, conversion from the first color space (YCbCr) of the input video signal to the second color space (RGB) is performed by matrix calculation.

Incidentally, the input video signal may include not only positive color values but also negative color values. Accordingly, the RGB data obtained by the matrix calculation may include negative color values.
In the conventional image processing apparatus, when converting from the YCbCr color space to the RGB color space, a negative color value that is a color value outside the color gamut of the RG color space (for example, 256 or more color values in the case of 8-bit data). ) Has been subjected to clipping processing to color values from 0 to 255.

  However, in a display device employing a conventional image processing apparatus, since negative color values are clipped, the negative color values are not reflected in the RGB data according to the display device. Can not hold the gradation and the number of colors represented by 256 or more color values, and the number of colors is reduced, so that the number of colors is smaller than that of the original video signal and the display is low gradation. There is a disadvantage that only images can be obtained.

  An object of the present invention is to provide an image processing apparatus and an image processing method capable of obtaining a display image corresponding to an original video signal without causing a decrease in the number of color specifications or a decrease in gradation.

  In order to achieve the above object, an image processing apparatus according to a first aspect of the present invention provides a color space of an input video signal including positive and negative color values from a first color space including positive and negative color values. A first conversion means for converting to a second color space, and a video signal from the first conversion means by signal processing reflecting the positive color value and the negative color value of the display device to be displayed. Second conversion means for converting to a color space compatible with the color gamut and outputting a converted video signal including only positive color values, wherein the second conversion means converts the converted video signal into a converted video signal. When the negative color value is included, the minimum component having the maximum absolute value among the plurality of components of the video signal is detected, and each of the converted video signals is based on the minimum component detected on the positive side. Add the ratio adjusted value to the component.

  An image processing apparatus according to a second aspect of the present invention converts a color space of an input video signal including positive and negative color values from a first color space to a second color space including positive and negative color values. First conversion means; first correction means for performing gamma correction on the video signal in the second color space by the first conversion means according to a display device corresponding to the input video signal; The video signal by the correction means 1 is converted into a color space corresponding to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value, and the positive color value Second conversion means for outputting a converted video signal including only the image signal, and second correction means for performing gamma correction in accordance with the display device to be displayed on the video signal by the second conversion means. The second conversion means converts the converted video signal into If the negative color value is included, the minimum component having the maximum absolute value among the plurality of components of the video signal is detected, and each of the converted video signals is based on the minimum component detected on the positive side. Add the ratio adjusted value to the component.

  An image processing apparatus according to a third aspect of the present invention provides a first conversion for converting a color space of an input video signal including positive and negative color values from a YCbCr color space to an RGB color space including positive and negative color values. And the video signal by the first conversion means are converted into an RGB color space that can correspond to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value. And a second conversion means for outputting a converted video signal including only positive color values, wherein the second conversion means includes the negative color value in the converted video signal. In this case, the minimum component having the maximum absolute value among the plurality of RGB components of the video signal is detected, and the ratio-adjusted value is added to each component of the converted video signal based on the minimum component detected on the positive side. .

  An image processing apparatus according to a fourth aspect of the present invention provides a first conversion for converting a color space of an input video signal including positive and negative color values from a YCbCr color space to an RGB color space including positive and negative color values. And a first correction unit for performing gamma correction on the video signal in the second color space by the first conversion unit according to the display device to which the input video signal corresponds, and the first correction unit. Is converted into an RGB color space compatible with the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value, and includes only positive color values. Second conversion means for outputting a converted video signal; and second correction means for performing gamma correction according to the display device to be displayed on the video signal by the second conversion means, The second conversion means is the one after conversion When the negative color value is included in the image signal, the minimum component having the maximum absolute value among the plurality of RGB components of the video signal is detected, and the converted result is based on the minimum component detected on the positive side. The ratio adjusted value is added to each component of the video signal.

  Preferably, the second conversion circuit adjusts the level of the video signal to which the ratio adjustment value is added with a gain that is lowered according to the ratio adjustment value, and outputs the video signal.

  Preferably, the second conversion circuit compares the luminance value of the video signal after the conversion and before the addition with the luminance value of the video signal after the addition to obtain the gain.

  An image processing method according to a fifth aspect of the present invention converts a color space of an input video signal including positive and negative color values from a first color space to a second color space including positive and negative color values. The video signal of the first step and the first step is converted into a color space that can correspond to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value. A second step of converting and outputting a converted video signal including only positive color values, and the negative color value is included in the converted video signal in the second step. Then, the minimum component having the maximum absolute value among the plurality of components of the video signal is detected, and the ratio-adjusted value is added to each component of the converted video signal based on the minimum component detected on the positive side.

According to the present invention, for example, a video signal including positive and negative color values is input to the first conversion means. In the first conversion means, the color space of the input video signal is converted from the first color space to the second color space including not only positive but also negative color values, and is output to the second conversion means.
In the second conversion means, the signal processing that reflects the positive color value and the negative color value is performed on the video signal by the first conversion means, thereby the color gamut of the display device to be displayed. Is converted into a color space compatible with In the second conversion means, when the converted video signal includes a negative color value, the minimum component having the maximum absolute value among the plurality of components of the video signal is detected. Then, a ratio-adjusted value is added to each component of the converted video signal with reference to the minimum component detected on the positive side.

  According to the present invention, there is an advantage that a display image corresponding to an original video signal can be obtained without causing a decrease in the number of colors and a decrease in gradation.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of an image display apparatus to which an image processing apparatus according to the present invention is applied.

  As shown in FIG. 1, the image display device 10 of the present embodiment includes an image input correction unit 11, a first conversion circuit 12, a first gamma (γ) correction circuit 13, a second conversion circuit 14, and a second conversion circuit 14. Γ correction circuit 15, display drive circuit 16, and display device 17 such as PDP or LCD.

  The image display device 10 is provided in, for example, a receiver for digital television broadcasting, and is a digital video that has been subjected to processing such as digital demodulation, error correction, demultiplexing, and decoding by frequency selection by a tuner (not shown). The signal is input to the image input correction unit 11 as a video signal (YCbCr) in the first color space.

When the component signal YCbCr is input as the video signal, the image input correction unit 11 simply separates the luminance signal Y and the color difference signals Cb and Cr from the component signal YCbCr and outputs them to the first conversion circuit 12.
The image input correction unit 11 converts the video signal RGB into the component signal YCbCr when the three primary color video signals RGB are input, and converts the luminance signal Y and the color difference signals Cb and Cr from the component signal YCbCr. It is possible to output separately.
The output video signal of the image input correction unit 11 includes not only positive color values but also negative color values.

Further, the image input correction unit 11 extracts the hue and saturation from the color difference signals Cb and Cr, and, for example, by referring to a correction amount lookup table in the factory setting, the correction according to the extracted hue and saturation is performed. A circuit for determining the quantity. For example, for an input video signal in the hue range corresponding to the skin color, the hue correction amount is slightly reddish, and at the same time, the correction amount is conspicuous by slightly increasing the saturation.
Then, the image input correction unit 11 corrects the video signal to the first conversion circuit 12 based on the determination result of the correction amount.
The image input correction unit 11 corrects the hue and saturation of the input video signal in real time. In this correction, the image input correction unit 11 limits the upper limit of the correction range to a predetermined level Vth so that image degradation due to saturation does not occur.

Further, the image input correction unit 11 determines the hue correction amount and the saturation correction amount of the input video signal independently of each other, and corrects the hue and saturation of the video signal independently of each other (only the hue). Correction, correction of only saturation, or correction of hue and saturation by different amounts).
Further, the image input correction unit 11 determines the correction amount so that the input video signal is corrected for a plurality of regions having different hues. Thereby, it is possible to correct two or more color regions without increasing the circuit scale.
Further, the image input correction unit 11 determines the correction amount over the entire angle range (0 ° to 360 °) on the so-called color difference plane as shown in FIG. Accordingly, a color region including a portion where the angle with respect to the X axis is 0 °, 90 °, 180 ° or 270 ° on the color difference plane, or a color region having an angle range with respect to the U axis exceeding 90 ° on the color difference plane. Can also be corrected.
Further, the image input correction unit 11 corrects the input video signal based on not only the correction amount determination result but also the luminance level of the input video signal. Thereby, a desired hue and saturation portion of the video signal can be arbitrarily corrected according to not only the hue and saturation but also the luminance level of the video signal.

The first conversion circuit 12 includes a video signal {Y: 10 (0) including positive and negative color values supplied from the image input correction unit 11. 8 2), Cb / Cr: s9 (s0 + 7 + 2)} is input, and the color space of the input video signal including the positive and negative color values is changed from the YCbCr color space (first color space) to the RGB color including the negative color values. Converted to a space (second color space), and the converted video signal {R: s13 (s1 8 4), G: s13 (s1 8 4), B: s13 (s1 8 4)} is output to the first γ correction circuit 13. Note that s indicates a sign.

The first γ correction circuit 13 is connected to a display device, for example, a CRT, to which the input video signal (input video signal) corresponds to the video signal (RGB data) in the second color space by the first conversion circuit 12. Corresponding gamma correction is performed, and the corrected linear image signal of RGB for CRT {R: s15 (s1 8 6), G: s15 (s1 8 6), B: s15 (s1 8 6)} is output to the second conversion circuit 14.

The second conversion circuit 14 can correspond to the color gamut of the display device 17 to be displayed by signal processing in which the video signal by the first γ correction circuit 13 reflects the positive color value and the negative color value. Video signal {R: 14 (0) converted to RGB color space and including only positive color values after conversion 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is output to the second γ correction circuit 15.

The second conversion circuit 14 converts the video signal {R: 14 (0 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is output to the second γ correction circuit 15 according to the control signal CTL, the first mode for clipping and outputting a negative color value from the converted video signal, and the converted video signal RGB If the negative color value is included in the negative color value, the R (maximum data) R or G or B component of the absolute value of each negative color value is detected, and the detected maximum R, A second mode in which the absolute value data of the G or B component is set to zero (0), the remaining data is applied with a so-called DC offset on the positive side, and the absolute value of the minimum value is added to each RGB component so that the ratio can be adjusted. Selectable.
Further, the second conversion circuit 14 has a function capable of adjusting the gain of the output video signal in accordance with the ratio adjustment when the second mode is selected.

  FIG. 3 is a block diagram illustrating a configuration example of the second conversion circuit 14 according to the present embodiment.

  The second conversion circuit 14 in FIG. 3 includes a conversion unit 141, an RGB minimum value detection unit 142, a negative signal processing unit 143, an adder 144, a gain control circuit 145, and an output gain adjustment unit 146.

  The conversion unit 141 is an RGB color space that can correspond to the color gamut of the display device 17 to be displayed by signal processing that reflects the positive color value and the negative color value of the video signal from the first γ correction circuit 13. To the RGB minimum value detection unit 142, the adder 144, and the gain control circuit 145.

The RGB minimum value detection unit 142 receives the RGB component of the video signal in the conversion unit 141, and when the converted video signal RGB includes a negative color value, among the negative color values of each component, Data having the maximum absolute value (minimum data) R, G, or B component is detected, and a detection result including a negative color value is detected as a signal S142 (s2 8 6) is supplied to the negative signal processing unit 143.

When the control signal CTL designates the first mode, the negative signal processing unit 143 clips the negative color value and outputs it to the adder 144.
When the control signal CTL designates the second mode, the negative signal processing unit 143 receives the detection signal S142 from the RGB minimum value detection unit 142, and detects the absolute value of the detected maximum R, G, or B component. The value data is set to zero (0), a so-called DC offset is applied to the remaining data on the positive side, and a signal S143 in which the ratio of the absolute value of the minimum value can be adjusted to each RGB component is output to the adder 144.

  FIG. 4 is a circuit diagram illustrating a configuration example of the negative signal processing unit 143. FIG. 4 shows a configuration for one channel of each of RGB.

The negative signal processing unit 143 in FIG. 4 includes an adder 1431, a sign extension unit 1432, and a selector 1433.
The negative signal processing unit 143 is configured to add the absolute value of the minimum value to RGB when the minimum value detected by the RGB minimum value detection unit 142 is negative.

The adder 144 adds the output signal S143 of the negative signal processing unit 143 to the converted video signal of the conversion unit 141, and generates a signal S144 (S3 8 6) Output to the gain control circuit 145 and the gain adjustment circuit 146.
In the first mode, since the output of the negative signal processing unit 143 is clipped with negative color values, the output of the adder 144 is the output video signal itself of the conversion unit 141.
In the second mode, the output of the negative signal processing unit 143 is a so-called DC offset in which the detected absolute value data of the maximum R, G, or B component is zero (0) and the remaining data is set to the positive side. Therefore, the signal is obtained by adjusting the ratio of the absolute value of the minimum value to each RGB component and becomes a video signal including data outside the color gamut of the display device 17.

The gain control circuit 145 obtains the luminance value Y1 of the video signal output from the conversion unit 141 and the luminance value Y2 of the video signal output from the adder 144, and compares the two.
The gain control circuit 145 determines that the output of the adder 144 remains the output of the conversion unit 141 in the first mode when there is no change in both luminance values as a result of the comparison, and the gain adjustment circuit 146 gain Is output to the gain adjustment circuit 146 to instruct to adjust the level of the video signal including only the positive color value to be output after the conversion with the preset gain G1.
In the second mode, the gain control circuit 145 applies a DC offset to the conversion unit 141 in the second mode when both luminance values are changed as a result of the comparison, and sets the absolute value of the minimum value to each RGB component. It is determined that the signal S143 for which the ratio can be adjusted is added, and the signal is output after conversion with the gain G2 (<G1) obtained by reducing the gain G1 set in advance according to the ratio adjustment value. A signal S145 for instructing the level adjustment of the video signal including only the positive positive color value is output to the gain adjustment circuit 146.

  Since the input data is RGB data, the gain control circuit 145 is configured to obtain the luminance values Y1 and Y2 based on the following formula.

(Equation 1)
Y = R (1/4 + 1/16) + G (1/2 + 1/16) + B (1/8)

  As shown in FIG. 3, the gain control circuit 145 includes a Y1 calculation unit 1451, a Y2 calculation unit 1452, and a comparison unit (Y1 / Y2) 1453.

  FIG. 5 is a circuit diagram showing a specific configuration example of the Y (Y1, Y2) calculation unit of FIG.

5 includes a 2-bit shifter 201, a 1-bit shifter 202, a 3-bit shifter 203, a 4-bit shifter 204, and adders 205 to 209.
The input signal format of the gain control circuit 145 is RGB, and in the case of the Y1 calculation unit 1451, s2 8 6 and s3 in the case of the Y2 calculation unit 1452 8 6.
Also in FIG. The part indicated by the reference numeral indicates the internal node extension bit, Y1 is s2, and Y2 is s3. In the case of bit extension, sign extension is performed.
Further, the shift calculation unit uses a value of 1/16 as a reference.

In the gain control circuit 145 of FIG. 5, R data is input to the 2-bit shifter 201 and the adder 205, B data is input to the 1-bit shifter 202, and G data is input to the 3-bit shifter 203 and the adder 207.
R data (1 / 16R (? 8 10)) is 1 / 4R (? 8 10) and input to the adder 205.
In the adder 205, the output of the 2-bit shifter 201 and the input R data are added, and data y1 (? 8 10) and output to the adder 208.
The B data input to the 1-bit shifter 202 is 1/8 (? 8 10) is input to the adder 206, and the data yb (? 8 10) is output to the adder 208.
In the adder 208, the output data of the adder 205 and the adder 206 are added, and the data yrb (? 8 10) is output to the adder 209.
The G data (1 / 16G (? 8 10)) is 1 / 2R (? 8 10) and input to the adder 207.
In the adder 207, the output of the 3-bit shifter 203 and the input G data are added, and data yg1 (? 8 10) and output to the adder 209.
In the adder 209, the output data of the adder 207 and the adder 208 are added, and data vy (? 8 10) is output to the 4-bit shifter 204.
And the data y from the 4-bit shifter 204 out (? 8 10).

  FIG. 6 is a circuit diagram illustrating a configuration example of the comparison unit (Y1 / Y2) of FIG.

The comparison unit 210 in FIG. 6 includes a divider 211, a clip unit 212, a register 213, and a selector 214.
In the divider 211, Y1 / Y2 is obtained. Since Y1 / Y2 is 1 or less, the clip unit 212 clips the step length portion of the division result.

The gain adjusting unit 146 has a gain corresponding to the gain control signal S145 from the gain control circuit 145, and the video signal {R: 14 (0) including only the positive color value after conversion output from the adder 144. 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is adjusted and output to the second γ correction circuit 15.
Since the RGB data after clipping a negative value is always positive, the sign is taken and the gain is multiplied by G.

The second γ correction circuit 15 receives the video signal {R: 14 (0 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is subjected to gamma correction according to the display device 17 on which the image is to be displayed, and the corrected video signal {R: 14 (0 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is output to the display drive circuit 16.

The display drive circuit 16 receives the video signal {R: 14 (0 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is processed into data suitable for driving the display device (for example, PDP) 17, and the processed video signal {R: 10 (0 8 2), G: 10 (0 8 2), B: 10 (0 8 2)} is output to the display device 17.

  Next, the operation according to the above configuration will be described.

For example, the component signal YCbCr is input to the image input correction unit 11 as a video signal, and the luminance signal Y and the color difference signals Cb and Cr are separated from the component signal YCbCr, so that not only positive color values but also negative color values are obtained. Is output to the first conversion circuit 12.
Further, the image input correction unit 11 extracts the hue and saturation from the color difference signals Cb and Cr in real time, determines a correction amount according to the extracted hue and saturation, and determines the input video signal according to the determined correction amount. Hue and saturation are corrected in real time. In this correction, the image input correction unit 11 limits the upper limit of the correction range to a predetermined level so that image degradation due to saturation does not occur.

In the first conversion circuit 12, the video signal including the positive and negative color values supplied from the image input correction unit 11 is input, and the color space of the input video signal including the positive and negative color values is the YCbCr color space. Conversion from (first color space) to RGB color space (second color space) including negative color values is performed.
Then, the converted video signal (with a sign) is output to the first γ correction circuit 13.

In the first γ correction circuit 13, the display device corresponding to the input video signal (input video signal) with respect to the video signal (RGB data) in the second color space by the first conversion circuit 12, for example, a CRT. A gamma correction is performed according to.
Then, the corrected CRT RGB linear video signal is output from the first γ correction circuit 13 to the second conversion circuit 14.

In the second conversion circuit 14, the video signal from the first γ correction circuit 13 is subjected to signal processing reflecting a positive color value and a negative color value, and the display device 17 to be displayed is displayed. It is converted into an RGB color space compatible with the color gamut.
Then, a video signal including only positive color values after conversion is output from the second conversion circuit 14 to the second γ correction circuit 15.
In the second conversion circuit 14, when a video signal including only positive color values after conversion is output to the γ correction circuit 15 of 2, a negative color value is converted from the converted video signal according to the control signal CTL. When the first mode to be clipped and output and the converted video signal RGB include negative color values, the data having the maximum absolute value (minimum data) among the negative color values. The R, G, or B component is detected, the detected absolute value data of the maximum R, G, or B component is set to zero (0), the remaining data is applied to the positive side by a so-called DC offset, and the absolute value of the minimum value The second mode for adding the value to each of the RGB components so that the ratio can be adjusted is controlled to be selectable.
In the second conversion circuit 14, the negative signal processing unit 143 outputs a signal S 143 corresponding to the processing in the first mode or the second mode to the adder 144.

In the adder 144, the output signal S143 of the negative signal processing unit 143 is added to the converted video signal of the conversion unit 141, and the signal S144 (S3 8 6) is output to the gain control circuit 145 and the gain adjustment circuit 146.
In addition processing in the adder 144, in the first mode, the output of the negative signal processing unit 143 is clipped with negative color values. Therefore, the output of the adder 144 becomes the output video signal itself of the conversion unit 141.
In the second mode, the output of the negative signal processing unit 143 is a so-called DC offset in which the detected absolute value data of the maximum R, G, or B component is zero (0) and the remaining data is set to the positive side. Therefore, the signal is obtained by adjusting the ratio of the absolute value of the minimum value to each RGB component and becomes a video signal including data outside the color gamut of the display device 17.

In the gain control circuit 145 of the second conversion circuit 14, the luminance value Y1 of the video signal output from the conversion unit 141 and the luminance value Y2 of the video signal output from the adder 144 are obtained, and both are obtained as described above. It is compared as a ratio according to the ratio adjustment.
The gain control circuit 145 determines that the output of the adder 144 remains the output of the conversion unit 141 in the first mode when there is no change in both luminance values as a result of the comparison. In this case, the ratio of Y1 / Y2 is 1.
Then, a signal S145 is output to the gain adjustment circuit 146 instructing the level adjustment of the video signal including only the positive color value to be output after the conversion with the gain G1 set in advance.

In the gain control circuit 145, if there is a change in both luminance values as a result of the comparison, the output of the adder 144 applies a DC offset to the conversion unit 141 in the second mode, and the absolute value of the minimum value is converted to each RGB component. It is determined that the signal S143 that enables the ratio adjustment is added to the signal. In this case, the ratio of Y1 / Y2 is a value smaller than 1.
Then, the level of the video signal including only the positive color value to be output after conversion is adjusted by the gain G2 (<G1) obtained by reducing the gain G1 in which the gain of the gain adjustment circuit 146 is set in advance according to the ratio adjustment value. A signal S145 is output to the gain adjustment circuit 146.

  The gain adjusting unit 146 adjusts the gain of the video signal including only the positive color value after the conversion output from the adder 144 with a gain corresponding to the gain control signal S145 by the gain control circuit 145, so that the second γ It is output to the correction circuit 15.

In the second γ correction circuit 15, gamma correction corresponding to the display device 17 on which an image is to be displayed is performed on the video signal from the second conversion circuit 14.
Then, the corrected video signal is output to the display drive circuit 16.

In the display drive circuit 16, the image data by the second γ correction circuit 15 is processed into data suitable for driving the display device (for example, PDP) 17, and the processed video signal is output to the display device 17. .
Thereby, the image display according to the color gamut which the display device 17 has is performed.

In the image display apparatus 10 having the above configuration, as shown in FIG. 7, the first conversion circuit 12 includes a video signal {Y: 10 including positive and negative color values supplied from the image input correction unit 11. (0 8 2), Cb / Cr: s9 (s0 + 7 + 2)} is input, and the color space of the input video signal including the positive and negative color values is changed from the YCbCr color space (first color space) to the RGB color including the negative color values. Converted to a space (second color space), and the converted video signal {R: s13 (s1 8 4), G: s13 (s1 8 4), B: s13 (s1 8 4)}, and the display corresponding to the input video signal (input video signal) with respect to the second color space video signal (RGB data) by the first conversion circuit 12 Gamma correction according to the device, for example, CRT is performed, and the corrected RGB linear video signal for CRT {R: s15 (s1 8 6), G: s15 (s1 8 6), B: s15 (s1 8 6)} and the display device 17 to display the video signal by the first γ correction circuit 13 by signal processing reflecting the positive color value and the negative color value. Video signal {R: 14 (0) including a positive color value after conversion to an RGB color space that can correspond to the color gamut of 8 6), G: 14 (0 8 6), B: 14 (0 8 6)} is output to the second γ correction circuit 15, the following effects can be obtained.

That is, as shown in FIG. 7, the negative color value is not clipped in the first conversion circuit 12 as in the conventional apparatus, and is supplied to the first γ correction circuit 13 and the second conversion circuit 14 in the subsequent stage. Then, the second conversion circuit 14 converts the RGB color space corresponding to the color gamut of the display device 17 to be displayed by the signal processing reflecting the positive color value and the negative color value. In the mode 1, it is possible to maintain the gradation and the number of colors outside the color gamut of the input video signal indicated by A in FIG. 8 and within the color gamut of the display device 17 indicated by B. A display image corresponding to the original video signal can be obtained without degrading the tone.
Further, in the second mode, in addition to the effects in the first mode, the gradation and the number of colors represented by the color values outside the color gamut of the display device 17 indicated by C in FIG. 8 are shown in FIG. There is an advantage that it can be positioned in the original color gamut of the display device 17 indicated by B and that a display image corresponding to the original video signal can be obtained.

  In the second mode, the image includes only the positive color value to be output after conversion with the gain G2 (<G1) obtained by reducing the gain G1 in which the gain of the gain adjustment circuit 146 is set in advance according to the ratio adjustment value. Since the signal level is adjusted, the level shifted to the positive side according to the minimum component can be lowered according to the adjustment ratio, so that the color of the video signal can be expressed more accurately. .

  The image input correction unit 11 corrects the hue and saturation of the input video signal in real time, and in this correction, the upper limit of the correction range is limited to a predetermined level so as not to cause image degradation due to saturation. Therefore, it is possible to obtain an image without image deterioration.

  Further, the image input correction unit 11 extracts the hue and saturation from the input video signal in real time, determines the correction amount corresponding to the extracted hue and saturation in real time, and inputs the input based on the determination result. Since the hue and saturation of the video signal are corrected in real time, the input video signal is extracted by extracting the hue and saturation of the input video signal, respectively, and determining the correction amount according to the extracted hue and saturation. The desired hue and saturation can be arbitrarily corrected in real time according to the hue and saturation.

  Also, since the hue correction amount and saturation correction amount of the input video signal are determined independently of each other, the hue and saturation of the video signal are corrected independently of each other (correcting only the hue or saturation). The hue and saturation can be corrected by different amounts).

  In addition, since the correction amount is determined so that the input video signal is corrected for a plurality of regions having different hues, two or more color regions can be corrected without increasing the circuit scale.

  In addition, since the correction amount is determined over the entire angle range (0 ° to 360 °) on the color difference plane, the portion where the angle image with respect to the U axis is 0 °, 90 °, 180 ° or 270 ° on the plane is determined. Correction can also be performed for a color area including the color area where the angle range with respect to the U-axis exceeds 90 ° on the color difference plane.

  In addition, since the input video signal is corrected based not only on the determination result of the correction amount but also on the luminance level of the input video signal, the desired hue and saturation of the video signal can be determined only by the hue and saturation. And can be arbitrarily corrected according to the luminance level of the video signal.

  In the above example, the hue of the input video signal is extracted using a lookup table, and the saturation of the input video signal is extracted using an arithmetic circuit. However, the present invention is not limited to this, and the hue of the input video signal may be extracted using an arithmetic circuit, or the saturation of the input video signal may be extracted using a lookup table.

  In the above example, the present invention is applied to a television broadcast receiver. However, the present invention is not limited to this, and the present invention may be applied to an imaging device such as a television camera, a video recording / reproducing device such as a DVD player, an editing device, and the like.

FIG. 1 is a block diagram showing the overall configuration of an image display apparatus to which an image processing apparatus according to the present invention is applied. It is a figure for demonstrating correction | amendment of a hue and saturation. It is a block diagram which shows the structural example of the 2nd conversion circuit which concerns on this embodiment. It is a circuit diagram which shows the structural example of a negative signal process part. FIG. 4 is a circuit diagram illustrating a specific configuration example of a Y (Y1, Y2) calculation unit in FIG. 3. FIG. 4 is a circuit diagram illustrating a configuration example of a comparison unit (Y1 / Y2) in FIG. 3. It is a figure which shows an example of the process containing the color value of each part in the image display apparatus of this embodiment. It is a figure for demonstrating the effect of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image display apparatus, 11 ... Image input correction | amendment part, 12 ... 1st conversion circuit, 13 ... 1st gamma ((gamma)) correction circuit, 14 ... 2nd conversion circuit, 15 ... 2nd gamma correction circuit, 16 ... display drive circuit, 17 ... display device.

Claims (13)

First conversion means for converting a color space of an input video signal including positive and negative color values from a first color space to a second color space including positive and negative color values;
The video signal by the first conversion means is converted into a color space that can correspond to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value, Second conversion means for outputting a converted video signal including only color values;
The second conversion means detects the minimum component having the maximum absolute value among the plurality of components of the video signal when the converted video signal includes the negative color value, and detects it on the positive side. An image processing apparatus that adds a ratio-adjusted value to each component of the converted video signal based on the minimum component. The image processing apparatus according to claim 1, wherein the second conversion circuit adjusts a level of a video signal to which the ratio adjustment value is added with a gain that is lowered according to the ratio adjustment value. The image processing apparatus according to claim 2, wherein the second conversion circuit obtains the gain by comparing the luminance value of the video signal after the conversion and before the addition with the luminance value of the video signal after the addition. First conversion means for converting a color space of an input video signal including positive and negative color values from a first color space to a second color space including positive and negative color values;
First correction means for performing gamma correction corresponding to a display device to which the input video signal corresponds with respect to the video signal in the second color space by the first conversion means;
The video signal by the first correction means is converted into a color space that can correspond to the color gamut of the display device to be displayed by signal processing that reflects the positive color value and the negative color value. Second conversion means for outputting a converted video signal including only color values;
Second correction means for performing gamma correction according to the display device to be displayed on the video signal by the second conversion means,
The second conversion means detects the minimum component having the maximum absolute value among the plurality of components of the video signal when the converted video signal includes the negative color value, and detects it on the positive side. An image processing apparatus that adds a ratio-adjusted value to each component of the converted video signal based on the minimum component. The image processing apparatus according to claim 4, wherein the second conversion circuit adjusts a level of a video signal to which the ratio adjustment value is added with a gain that is lowered according to the ratio adjustment value. The image processing apparatus according to claim 5, wherein the second conversion circuit compares the luminance value of the video signal after the conversion and before the addition with the luminance value of the video signal after the addition to obtain the gain. First conversion means for converting a color space of an input video signal including positive and negative color values from a YCbCr color space to an RGB color space including positive and negative color values;
The video signal by the first conversion means is converted into an RGB color space that can correspond to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value. Second conversion means for outputting a converted video signal including only the color value of
The second conversion means detects a minimum component having a maximum absolute value among a plurality of RGB components of the video signal when the converted video signal includes the negative color value, and sets the positive side to the positive side. An image processing apparatus that adds a ratio-adjusted value to each component of the converted video signal based on the detected minimum component. The image processing apparatus according to claim 7, wherein the second conversion circuit adjusts a level of a video signal added with the ratio adjustment value with a gain that is lowered according to the ratio adjustment value. The image processing apparatus according to claim 8, wherein the second conversion circuit obtains the gain by comparing the luminance value of the video signal after the conversion and before the addition with the luminance value of the video signal after the addition. First conversion means for converting a color space of an input video signal including positive and negative color values from a YCbCr color space to an RGB color space including positive and negative color values;
First correction means for performing gamma correction corresponding to a display device to which the input video signal corresponds with respect to the video signal in the second color space by the first conversion means;
The video signal by the first correction means is converted into an RGB color space that can correspond to the color gamut of the display device to be displayed by signal processing that reflects the positive color value and the negative color value. Second conversion means for outputting a converted video signal including only the color values of
Second correction means for performing gamma correction according to the display device to be displayed on the video signal by the second conversion means,
The second conversion means detects a minimum component having a maximum absolute value among a plurality of RGB components of the video signal when the converted video signal includes the negative color value, and sets the positive side to the positive side. An image processing apparatus that adds a ratio-adjusted value to each component of the converted video signal based on the detected minimum component. The image processing apparatus according to claim 10, wherein the second conversion circuit adjusts a level of a video signal added with the ratio adjustment value with a gain that is lowered according to the ratio adjustment value. The image processing apparatus according to claim 11, wherein the second conversion circuit obtains the gain by comparing the luminance value of the video signal after the conversion and before the addition with the luminance value of the video signal after the addition. A first step of converting a color space of an input video signal including positive and negative color values from a first color space to a second color space including positive and negative color values;
The video signal in the first step is converted into a color space that can correspond to the color gamut of the display device to be displayed by signal processing reflecting the positive color value and the negative color value, and the positive color value is obtained. A second step of outputting a converted video signal including only the value,
In the second step, when the converted video signal includes the negative color value, the minimum component having the maximum absolute value among the plurality of components of the video signal is detected and detected on the positive side. An image processing method in which a ratio-adjusted value is added to each component of the converted video signal based on the minimum component.

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