CN101873502A - Color space converting circuit and method thereof - Google Patents

Color space converting circuit and method thereof Download PDF

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Publication number
CN101873502A
CN101873502A CN200910106780A CN200910106780A CN101873502A CN 101873502 A CN101873502 A CN 101873502A CN 200910106780 A CN200910106780 A CN 200910106780A CN 200910106780 A CN200910106780 A CN 200910106780A CN 101873502 A CN101873502 A CN 101873502A
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color space
pixel component
converting circuit
critical value
circuit according
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CN101873502B (en
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蔡孟哲
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MStar Software R&D Shenzhen Ltd
MStar Semiconductor Inc Taiwan
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MStar Software R&D Shenzhen Ltd
MStar Semiconductor Inc Taiwan
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Abstract

The invention relates to a color space converting circuit and a method thereof. In the invention, when an xvYcc color space is transformed into a sRGB color space, by adopting a simplified circuit design, the part beyond the sRGB color space is compressed into the sRGB color space so as to promote the visual effect. The color space converting circuit comprises a converting unit, and the converting unit can transform a pixel signal from the xvYcc color space into the sRGB color space. During the transformation process, the converting unit generates the pixel component of the pixel signal on the color space dimensionalities of the sRGB color space; when any one pixel component is positioned in a compression region, the converting unit compresses the pixel component so as to output a compressed pixel component; and the compressed pixel component does not exceed over the coverage scope of the sRGB color space on the corresponding color space dimensionality.

Description

Color space converting circuit and method
Technical field
Present invention is directed to color space conversion (color space conversion), refer to a kind of color space converting circuit and method especially.
Background technology
YCbCr and sRGB (standard RGB) are standard color space commonly used, in practical application, for instance, the video signal of the exportable YCbCr form of device for image (as digital video camera or DVD player etc.) is to display unit (as digital TV etc.), display unit is converted into the sRGB form again, to show.In CCIR Recommendation 601 specifications, each encodes Y (lightness), Cb and Cr (chroma) with 8 positions, and wherein the scope of Y is 16～235, and the scope of Cb, Cr respectively is 16～240.When the YCbCr color space is converted to the sRGB color space, utilize following conversion formula:
R ′ G ′ B ′ = 0.00456621 0 . 0.00625893 0.00456621 - 0.00153632 - 0.00318811 0.00456621 0.00791071 0 . · ( Y 601 ′ C B C R - 16 128 128 )
The scope that can learn redness (R), green (G), blue (B) component is respectively 0～1, represents to be 0～255 scope with 8.
Because the consumer improves day by day to the requirement of visual effect, the YCbCr color space does not gradually apply and uses, so in recent years, based on the YCbCr color space, develop and xvYcc (eXtended Video YCC, or be called x.v.Color) color space, its colour gamut is about 1.8 times big of former YCbCr color space, so that more abundant colors performance to be provided.In the xvYcc color space, if encode with 8 equally, then the scope of Y, Cb and Cr respectively can expand as 1～254.If according to aforementioned conversion formula the scope of this expansion is changed, then the scope of R, G, B component also expands as-17.46～277 respectively, as shown in Figure 1.Yet, exceed 0～255 part, promptly-17.46～0 and 255～277 part, and can't be with 8 bit representations.Prior art system will-17.46～0 part all give up and be considered as 0,255～277 part and all give up and be considered as 255, make that the broad colour gamut of xvYcc color space can't fully performance in the sRGB color space, and can't promote visual effect.
Summary of the invention
In view of this, one of the present invention purpose, be to provide a kind of color space converting circuit and method, can be when carrying out the xvYcc color space to the conversion of sRGB color space, with the circuit design of simplifying, the part that will exceed the sRGB color space is compressed in the sRGB color space, to promote visual effect.
The invention provides a kind of color space converting circuit, in order to a pixel signal is converted to second color space from first color space, second color space has at least one color space dimension.This color space converting circuit comprises: converting unit, in order to the pixel component of generation pixel signal on this color space dimension, and when pixel component is positioned between a compressional zone, pixel component is compressed with output packed pixel component; Wherein, the packed pixel component does not exceed the covering scope of second color space on this color space dimension.
The present invention provides a kind of color space changover method in addition, comprises the following step: reception one belongs to the pixel signal of first color space; Produce the pixel component of pixel signal on the color space dimension of second color space; And when pixel component is positioned between a compressional zone, pixel component is compressed with output packed pixel component, wherein the packed pixel component does not exceed the covering scope of second color space on its color space dimension.
Description of drawings
Fig. 1 is the schematic diagram that shows the relative size of YCbCr color space and xvYcc color space.
Fig. 2 is the calcspar of one of the present invention's color space converting circuit embodiment.
Fig. 3 is the schematic diagram how converting unit of displayed map 2 carries out compressed action.
Fig. 4 is the flow chart of one of the present invention's color space changover method embodiment.
Among the figure, the 20th, color space converting circuit, the 21, the 22nd, buffer, the 23rd, converting unit, the 24th, buffer unit, 41～45th, the process step of one of color space changover method embodiment.
Embodiment
Fig. 2 is the calcspar of one of the present invention's color space converting circuit 20 embodiment, comprises a buffer unit 24 and a converting unit 23.Color space converting circuit 20 can be carried out the conversion of xvYcc color space (hereinafter referred xvYcc) to sRGB color space (hereinafter referred sRGB).SRGB has three color space dimensions, promptly red, green, blue dimension.SRGB all has a covering scope in each dimension, and this covering scope has a lower limit and a higher limit (hereinafter being called first lower limit and first higher limit), if represent with 8, is respectively 0 and 255.When xvYcc was converted to sRGB, xvYcc also each tool one lower limit and higher limit (hereinafter being called second lower limit and second higher limit) on red, green, blue dimension as if with 8 bit representations, were respectively-17.46 and 277.Therefore, second lower limit is less than first lower limit, and second higher limit is greater than first higher limit.
Buffer unit 24 can comprise buffer 21 and 22.Buffer 21 stores first critical value and first slope, and buffer 22 stores second critical value and second slope, and first critical value is greater than second critical value.Buffer 21,22 these stored parameters can be adjusted according to actual needs.Converting unit 23 is coupled to buffer 21,22, can be according to the stored parameter value of buffer 21,22, with an input pixel signal that belongs to xvYcc, export after being converted to the output pixel signal that belongs to sRGB.In this transfer process, converting unit 23 will be imported the pixel component on each color space dimension that the pixel signal is converted to sRGB, i.e. red component, green component and blue component earlier.Then, converting unit 23 judges whether the size of each pixel component is positioned between the compressional zone, if then compress; Otherwise, do not compress.In other words, the pixel value interval that representative need be compressed between the compressional zone.In this embodiment, comprise between the compressional zone: the lower limit and the upper limit are respectively the pixel value interval of first critical value and second higher limit, and lower limit and the upper limit are respectively the pixel value interval of second lower limit and second critical value.Therefore, the big I between the compressional zone is adjusted by changing first critical value or second critical value.When arbitrary pixel component (as red component) greater than first critical value and when being not more than second higher limit (as limit value on xvYcc is on red dimension), 23 pairs of these pixel component of converting unit are carried out first compressed action to export the first packed pixel component, make the packed pixel component of winning not be higher than first higher limit (as sRGB limit value on the red dimension), and between the first packed pixel component and this pixel component for having the linear relationship of first slope; When arbitrary pixel component less than second critical value and when being not less than second lower limit, 23 pairs of these pixel component of converting unit are carried out second compressed action to export the second packed pixel component, make the second packed pixel component be not less than first lower limit, and the second packed pixel component and this pixel component are for having the linear relationship of second slope; On the other hand, 23 pairs of arbitrary pixel component between between first critical value and second critical value of converting unit are not then carried out any compressed action, directly export this pixel component.Therefore, in the output pixel signal that converting unit 23 is exported, redness, green and blue component are all in the gamut range of sRGB.
Fig. 3 shows how converting unit 23 carries out the schematic diagram of compressed action, wherein, the input pixel component for the input pixel signal of Fig. 2 changed redness, green and blue component one of them, the output pixel component by the output pixel signal of Fig. 2 comprised redness, green and blue component one of them.In Fig. 3, when the input pixel component greater than first critical value and be not more than second higher limit, perhaps, less than second critical value and when being not less than second lower limit, can be compressed to produce the output pixel component, so, the pixel component that surpasses the sRGB gamut range originally can be compressed in the sRGB gamut range, manifesting the color of different levels, and can not handled as same color.For instance, the red component of 260 and 270 (all surpassing 255 the upper limit) after handling through overcompression, can present the redness of different levels, and can all do not shown by the redness as 255.Fig. 3 has shown two kinds of compress modes, and in this embodiment, one is curve compression (curve compression), and another is linear compression (linear compression).Preferably, the curve compression produces according to the Gamma curve, to meet the vision of human eye.Perhaps, in the present invention's color space converting circuit 20, come the approximating curve compression, so can reduce circuit cost, and reach the visual effect very approximate with the curve compression in the mode of linear compression.
In this embodiment, the oblique line between first critical value and second higher limit, its slope are first slope, and aforementioned first compressed action is promptly carried out linear compression according to first slope, that is:
Output pixel component (i.e. the first packed pixel component)=(input pixel component-first critical value) * first slope+first critical value formula (1)
Oblique line between second critical value and second lower limit, its slope are second slope, and aforementioned second compressed action is promptly carried out linear compression according to second slope, that is:
Output pixel component (i.e. the second packed pixel component)=(input pixel component-second critical value) * second slope+second critical value formula (2)
Formula (1) can be considered carries out linear interpolation (linearinterpolation) between first critical value and second higher limit, formula (2) can be considered between second critical value and second lower limit carries out linear interpolation.Preferably, change-over circuit 23 comprises interpolating circuit (figure does not show), in order to the linear interpolation computing of execution formula (1) with formula (2).
In the formula (1), when input pixel component and the first packed pixel component are respectively second higher limit and first higher limit, if first critical value is known, then first slope can produce by first critical value, first higher limit and the second higher limit substitution formula (1) are derived; If first slope is known, then first critical value can produce by first slope, first higher limit and the second higher limit substitution formula (1) are derived.In like manner, in the formula (2), when input pixel component and the second packed pixel component were respectively second lower limit and first lower limit, if second critical value is known, then second slope can be by generation that second critical value, first lower limit and the second lower limit substitution formula (2) are derived; If second slope is known, then second critical value can produce by second slope, first lower limit and the second lower limit substitution formula (2) are derived.Therefore, under this kind situation, buffer 21 only need store first critical value and the first slope one, and buffer 22 only need store second critical value and the second slope one, and storage person can not produce by deriving, and so can save memory space.
In another specific embodiment, converting unit 23 comprises a question blank (lookup table, figure does not show), in order to store the output pixel component of input pixel component and correspondence, wherein, when the input pixel component greater than first critical value and when being not more than second higher limit, the output pixel component of correspondence is the first packed pixel component; When the input pixel component less than second critical value and when being not less than second lower limit, the output pixel component of correspondence is the second packed pixel component; When importing pixel component between first critical value and second critical value, the output pixel component of correspondence is the input pixel component of script.Therefore, converting unit 23 can be carried out first compressed action and second compressed action apace according to this question blank.
Preferably, produce redness, green and blue component for the input pixel signal of xvYcc through conversion, converting unit 23 can be used different critical values and slope respectively, carries out aforementioned linear compression.Critical value that these are different and slope can be stored in the buffer 21,22.
Because HDMI (High Definition Multimedia Interface) (High-definition Multimedia Interface, HDMI) in the specification of its 1.3 version, begin to support xvYcc, the present invention's color space converting circuit 20 is applicable to the HDMI receiver, signal in order to xvYcc form that the HDMI receiver is received, be converted to the signal of sRGB form, on display unit such as digital TV, show.
Fig. 4 is the flow chart of one of the present invention's color space changover method embodiment, is used for the conversion of first color space to the second color space.This method comprises the following step:
Step 41: reception one belongs to the pixel signal of first color space.
Step 42: produce the pixel component of this pixel signal on each color Spatial Dimension of second color space.
Step 43: when the pixel component on arbitrary color space dimension greater than first critical value and when being not more than on this pixel component limit value, this pixel component is carried out first compressed action to export the first packed pixel component, wherein the first packed pixel component is not higher than second color space limit value on this color space dimension, and between the first packed pixel component and this pixel component for having the linear relationship of first slope.
Step 44: when the pixel component on arbitrary color space dimension less than second critical value and when being not less than under this pixel component limit value, this pixel component is carried out second compressed action to export the second packed pixel component, wherein the second packed pixel component is not less than second color space limit value under on this color space dimension, and between the second packed pixel component and this pixel component for having the linear relationship of second slope.
Step 45: when the pixel component on arbitrary color space dimension is between first critical value and second critical value, directly export this pixel component.
In the abovementioned steps, first critical value is greater than second critical value; The higher limit of the pixel component on arbitrary color space dimension is greater than second color space limit value on this color space dimension; The lower limit of the pixel component on arbitrary color space dimension is less than second color space limit value under on this color space dimension.
Preferably, first color space is the xvYcc color space, and second color space is the sRGB color space, and it comprises three color space dimensions such as redness, green and blue dimension.The color space changover method of Fig. 4 can be applied to the HDMI receiver.
Preferably, step 43～45 are to carry out according to a question blank.This question blank is the pixel component of the difference size that produced of storing step 42 and the pixel component of step 43～45 a corresponding output in advance, promptly the former pixel component of the first packed pixel component, the second packed pixel component or uncompressed so can be accelerated the execution speed of step 43～45.
The above is to utilize preferred embodiment to describe the present invention in detail, and unrestricted the present invention's scope.Allly know this skill personage and all can understand, can make many may the variation, still do not break away from the present invention's spirit and scope according to the announcement of above embodiment.

Claims (20)

1. a color space converting circuit is characterized in that, comprises:
One converting unit, in order to a pixel signal is converted to one second color space from one first color space, this second color space has at least one color space dimension;
Wherein, this converting unit produces this pixel signal pixel component one of on this color space dimension, and when this pixel component is positioned between a compressional zone, this pixel component is compressed to export a packed pixel component, made this packed pixel component not exceed this second color space covering scope one of on this color space dimension.
2. color space converting circuit according to claim 1 is characterized in that, in the time of outside this pixel component is positioned between this compressional zone, this converting unit is directly exported this pixel component.
3. color space converting circuit according to claim 1 is characterized in that this converting unit comprises a question blank, in order to store this packed pixel component of this pixel component and correspondence; This converting unit is compressed this pixel component according to this question blank.
4. color space converting circuit according to claim 1 is characterized in that, is a linear relationship between this packed pixel component and this pixel component.
5. color space converting circuit according to claim 4 is characterized in that, more comprises:
One buffer unit is coupled to this converting unit, in order to store one of this linear relationship slope.
6. according to claim 1 or 4 described color space converting circuits, it is characterized in that, between this compressional zone under the limit with the upper limit be respectively one of one first critical value and this pixel component higher limit, this packed pixel component is not higher than one of this covering scope higher limit.
7. color space converting circuit according to claim 6 is characterized in that, this higher limit of this pixel component is greater than this higher limit of this covering scope.
8. color space converting circuit according to claim 6 is characterized in that, this packed pixel component system determines according to one of this pixel component, this first critical value and this linear relationship slope.
9. color space converting circuit according to claim 6 is characterized in that, more comprises:
One buffer unit is coupled to this converting unit, in order to store this first critical value.
10. color space converting circuit according to claim 6 is characterized in that, one of this linear relationship slope is to determine according to this higher limit of this higher limit of this first critical value, this pixel component and this covering scope.
11. according to claim 1 or 4 described color space converting circuits, it is characterized in that, between this compressional zone on the limit with lower limit be respectively one of one second critical value and this pixel component lower limit, this packed pixel component is not less than one of this covering scope lower limit.
12. color space converting circuit according to claim 11 is characterized in that, this lower limit of this pixel component is less than this lower limit of this covering scope.
13. color space converting circuit according to claim 11 is characterized in that, this packed pixel component system determines according to one of this pixel component, this second critical value and this linear relationship slope.
14. color space converting circuit according to claim 11 is characterized in that, more comprises:
One buffer unit is coupled to this converting unit, in order to store this second critical value.
15. color space converting circuit according to claim 11 is characterized in that, one of this linear relationship slope is to determine according to this lower limit of this lower limit of this second critical value, this pixel component and this covering scope.
16. color space converting circuit according to claim 1 is characterized in that, this first color space is the xvYcc color space, and this second color space is the sRGB color space.
17. color space converting circuit according to claim 16 is characterized in that, this color space converting circuit system is implemented in a HDMI (High Definition Multimedia Interface) (HDMI) receiver.
18. a color space changover method is characterized in that, comprises:
Reception one belongs to the pixel signal of one first color space;
This pixel signal is converted to one second color space one of to produce on one of this second color space color space dimension pixel component from this first color space; And
When this pixel component is positioned between a compressional zone, this pixel component is compressed to export a packed pixel component, make this packed pixel component not exceed this second color space covering scope one of on this color space dimension.
19. color space changover method according to claim 18 is characterized in that, this compression step system carries out according to a question blank, and wherein this question blank stores this packed pixel component of this pixel component and correspondence.
20. color space changover method according to claim 18 is characterized in that, between this compressional zone under the limit with the upper limit be respectively one of one first critical value and this pixel component higher limit, this packed pixel component is not higher than one of this covering scope higher limit.
CN200910106780.7A 2009-04-24 2009-04-24 Color space converting circuit and method Expired - Fee Related CN101873502B (en)

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CN103763538A (en) * 2014-02-21 2014-04-30 深圳创维－Rgb电子有限公司 Method and device for displaying signal colors
CN104581102A (en) * 2013-10-09 2015-04-29 联咏科技股份有限公司 Color converting method and color converting system
CN106887218A (en) * 2017-03-22 2017-06-23 深圳市华星光电技术有限公司 Color conditioning method and regulating system based on color gamut display high
CN110188680A (en) * 2019-05-29 2019-08-30 南京林业大学 Tea tree tender shoots intelligent identification Method based on factor iteration

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US8085277B2 (en) * 2004-01-30 2011-12-27 Broadcom Corporation System and method for clipping values of pixels in one color space so not to exceed the limits of a second color space
JP4534917B2 (en) * 2005-09-08 2010-09-01 ソニー株式会社 Color gamut compression method, program, and color gamut compression device
KR101287039B1 (en) * 2005-10-14 2013-07-23 삼성디스플레이 주식회사 Improved gamut mapping and subpixel rendering system and method
US8295594B2 (en) * 2007-10-09 2012-10-23 Samsung Display Co., Ltd. Systems and methods for selective handling of out-of-gamut color conversions

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CN104581102A (en) * 2013-10-09 2015-04-29 联咏科技股份有限公司 Color converting method and color converting system
CN103763538A (en) * 2014-02-21 2014-04-30 深圳创维－Rgb电子有限公司 Method and device for displaying signal colors
CN103763538B (en) * 2014-02-21 2016-08-31 深圳创维－Rgb电子有限公司 A kind of realize the method and device that signal colour shows
CN106887218A (en) * 2017-03-22 2017-06-23 深圳市华星光电技术有限公司 Color conditioning method and regulating system based on color gamut display high
CN106887218B (en) * 2017-03-22 2019-10-25 深圳市华星光电技术有限公司 Color conditioning method and regulating system based on high color gamut display
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CN110188680B (en) * 2019-05-29 2021-08-24 南京林业大学 Tea tree tender shoot intelligent identification method based on factor iteration

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