JP2008270859A - Gradation correction processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a false outline is formed in an area where an correction amount for an input signal increases or decreases when some part abruptly increases or decreases in correction amount relative to other parts as to gradation correction amounts of respective pixels. <P>SOLUTION: A false outline area detecting unit 3 detects differences in gradation correction amount between a pixel of interest and upper and lower, and right and left pixels for input image data 1, a value of a gradation correction amount on a side where a difference value is large is regarded as a weight of intensity of a false outline, and a gradation correction amount found by a gradation correction amount detecting unit 2 is decreased according to the weight to make the correction amount small, thereby suppressing a false outline. Consequently, while the false outline generated as the gradation correction amount abruptly increases or decreases is suppressed, effects of gradation correction is maintained in a case wherein no false outline is generated. Thus, the false outline generated in the gradation correction can be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a television receiver such as a plasma display and a color image display device, and detects a false contour region from transition information of a correction amount when performing gradation correction on input image data. The present invention relates to a gradation correction processing apparatus that suppresses the effect of gradation correction.

  Conventionally, the technology to adjust the brightness and chromaticity by moving the brightness value and chromaticity value distributed in a specific color area to another brightness and color for received video signals and captured images, etc. Has been used.

Further, as described in Patent Document 1, a color region portion that applies to a human memory color such as human skin, lawn, or blue sky is detected in a three-axis space of hue, saturation, and brightness, and hue, saturation, Lightness is shifted to the color ideal for humans.
Japanese Patent Laid-Open No. 2-96477

  Here, the problem in Patent Document 1 described above will be described with reference to FIGS. FIG. 2A shows the tone correction amount in a predetermined image space, while FIG. 2B shows the case where the tone correction amount shown in FIG. 2A is applied to the input signal. The signal level displayed on the screen in a predetermined image space is shown.

  Here, in the gradation correction amount of each pixel as shown in FIG. 2 (a), when the correction amount suddenly increases or decreases for one part relative to the other part, the input is made as shown in (b). A false contour occurs in a region where the correction amount suddenly increases or decreases with respect to the signal. An object of the present invention is to suppress the false contour generated when the gradation correction amount as described above is rapidly increased or decreased, and to maintain the effect of the gradation correction when no false contour is generated.

  In order to solve the above problems, the present invention focuses on the gradation correction amount obtained from the input signal, detects the false contour region from the difference in the gradation correction amount between the target pixel and the adjacent upper, lower, left and right pixels, and When the difference in tone correction amount is large, the gradation correction suppression amount is increased. Conversely, in the portion where the gradation correction amount difference is small, the gradation correction suppression amount is decreased to maintain the correction effect, and false contour suppression and gradation are maintained. It is characterized by both correction effects.

  As described above, according to the present invention, it is possible to suppress the false contour that occurs when the gradation correction amount suddenly increases or decreases, and to maintain the gradation correction effect in a region where no false contour occurs. Become.

  In the first invention, a change amount of the gradation correction amount with respect to the input image data is detected, and the gradation correction amount is suppressed by a difference value between the gradation correction amount of the pixel of interest and the gradation correction amount of the adjacent pixel, and false. This is a gradation correction device that suppresses the occurrence of contours.

  The second invention is an apparatus that detects a difference value between the gradation correction amount of the target pixel and the gradation correction amounts of the upper, lower, left, and right pixels, and calculates a weight indicating the intensity of the false contour based on the difference value.

(Embodiment 1)
FIG. 1 is a block diagram of a gradation correction apparatus according to the present invention. In FIG. 1, reference numeral 1 indicates input image data such as an input video signal, and 2 indicates an amount (gain) for correcting the gradation of a certain luminance or chromaticity region according to the value of the input video signal. The gradation correction amount detection means 3 performs the false contour region detection means 3 for detecting the strength of the false contour in the target pixel from the change amount of the gradation correction amount, and 4 indicates the gradation detected by the correction amount detection means 2. A tone correction amount adjusting unit that suppresses the tone correction amount so that a false contour does not occur by combining the gain of the false contour region detected by the region detecting unit 3 with the correction amount. A correction component synthesizing unit for adding a tone correction gain in which the tone correction amount is suppressed so as not to generate a false contour by the tone correction amount adjusting unit 4, and 6 is output image data after tone correction. Although not shown, a buffer is provided while the input image data 1 is input to the correction component synthesis unit 5, and the above-described gradation correction amount detection unit 2, false contour region detection unit 3, floor The adjustment time adjustment unit 4 adjusts the time required for processing.

  A specific operation in such a configuration will be described below with reference to FIG.

  The input image data is input to the gradation correction amount detection unit 2 and the correction component synthesis unit 5. The false contour region detection means 3 has left and right pixels (i−1, j) adjacent to the target pixel in the 3 × 3 region of 3 × 3 pixels as shown in FIG. 3 where the target pixel is (i, j). ), (I, j), (i + 1, j), adjacent upper and lower pixels (i, j-1), (i, j), (i, j + 1), and divided horizontally and vertically To detect.

  At this time, the false contour gains G_h and G_v in the horizontal direction and the vertical direction are expressed by the following detection expressions.

G_h = max {| (i, j)-(i-1, j) |, | (i, j)-(i + 1, j) |}
G_v = max {| (i, j)-(i, j-1) |, | (i, j)-(i, j + 1) |}
These false contour gains in the horizontal and vertical directions are added as follows to obtain a false contour gain G in the pixel of interest. G = G_h + G_v
The gradation correction amount adjusting means 4 uses the G value obtained by the false contour region detection means 3 to the gradation correction amount C detected by the gradation correction amount detection means 2 and after gain adjustment by the following formula: A gradation correction amount C ′ is obtained.

C ′ = C × (1-G / N) (N: constant)
The correction component synthesizing unit 5 adds the correction gain output from the gradation correction amount adjusting unit 4 to the input image data 1 as follows to obtain output data.

  For example, in the horizontal direction, the input signal values of each pixel shown in FIG. 4 are (i−2, j) = 10, (i−1, j) = 20, (i, j) = 30, (i + 1, j). = 35, (i + 2, j) = 40. In this case, the gradation correction amount will be described. The gradation correction gains are C_ (i−2, j) = 0, C_ (i−1, j) = 20, C_ (i, j) = 25, C_ (i + 1, j) = 30, C_ (i + 2, If j) = 0, the hue values after gradation correction are (i−1, j) ′ = 40, (i, j) ′ = 55, and (i + 1, j) ′ = 65 (i− 2, j) and (i−1, j), the signal value difference is 10 to 30, and the difference is larger than the other areas, resulting in a false contour.

Therefore, using the above detection formula, G_h (i-1) = max {| 20-0 |, | 20-25 |} becomes G_h (i-1) = 20, and the correction gain is detected from this value as follows. Using the equation, C ′ (i−1) = 20 × (1-20 / 32) (when N = 32) to C ′ (i−1) = 7, and the false contour is suppressed. Note that an arbitrary suppression rate can be set by changing the constant N in the detection formula of the corrected correction gain C ′.

  As described above, the gradation correction apparatus according to the present invention suppresses false contours by adjusting the gradation correction amount from the transition information of the gradation correction amount between the target pixel and the peripheral pixels when performing gradation correction, thereby preventing false contours. In an area where no contour occurs, the effect of gradation correction can be maintained as it is.

  Note that although processing for each pixel has been described in this embodiment, the present invention is not limited to this, and processing can be performed for each of a plurality of pixels. This speeds up the tone correction process.

  The present invention is not limited to any type as long as it outputs and displays an image, and examples thereof include a plasma display and an LCD (liquid crystal display).

  As described above, the gradation correction apparatus according to the present invention suppresses false contours by adjusting the gradation correction amount from the transition information of the gradation correction amount between the target pixel and the peripheral pixels when performing gradation correction, thereby preventing false contours. It has a function to keep the effect of gradation correction as it is in an area where no outline is generated, and it is used as a gradation correction processing apparatus that suppresses false outline due to gradation correction in a television receiver such as a plasma display or a color image display device. Useful.

The figure which showed the block diagram of the gradation correction apparatus which is one embodiment of this invention The figure which showed the false contour by gradation correction amount and gradation correction to the input signal The figure which showed the area | region for false contour detection from the gradation correction amount in the same apparatus The figure which showed the effect at the time of adjusting the false outline and gradation correction amount by gradation correction in the same device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input image data 2 Tone correction amount detection part 3 False contour area detection part 4 Tone correction amount adjustment part 5 Correction component composition part 6 Output image data

Claims (2)

In an image display device, a device for correcting gradation of luminance or chromaticity of a color image,
A gradation correction amount detection unit that detects the gradation correction amount based on the luminance or chromaticity value of the input image data, and a false that detects a false contour region by gradation correction from the transition state of the correction amount of adjacent upper, lower, left and right pixels An outline detector;
In a region where a false contour occurs, a gradation correction amount adjustment unit that adjusts the gradation correction amount from the weight value obtained in advance by the false contour detection unit and suppresses the generation of false contours due to gradation correction;
A gradation correction apparatus including a correction component combining unit that combines input image data and a gradation correction amount to generate output image data. In the false contour region detection unit, the difference between the gradation correction amount of the adjacent pixel and the gradation correction amount of the adjacent pixel is obtained with respect to the gradation correction amount of the pixel of interest, and the difference value on the side where the difference is larger is used as the false contour strength in the horizontal direction. The difference between the upper and lower pixels adjacent to the target pixel is obtained as a weight, and the difference value on the side with the larger difference is used as the weight of the false contour strength in the vertical direction. The tone correction device.

Images