Color enhancement for digital images
AssigneeQUALCOMM Icorporated
InventorsSzepo Robert Hung, Xiaoyun Jiang, Hsiang-Tsun Li
Life of this patent
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Abstract
Techniques for identifying and enhancing colors in a digital image associated with one or more target color shades. In an embodiment, the target color shades may include a shade of blue associated with the sky, a shade of green associated with outdoor foliage, or the color red. In an embodiment, the blue chroma (Cb) and red chroma (Cr) coordinates of a pixel are evaluated to determine whether to apply an enhancement factor. The enhancement factor may incorporate an exposure index (EI) auxiliary enhancement factor, a color temperature (D) auxiliary enhancement factor, and a luminance (Y) of each pixel. Further aspects for implementing the techniques in software and hardware are disclosed.
Claims30
A method for evaluating and enhancing the color of pixels in a digital image, each pixel having associated Y-Cb-Cr coordinates, the method comprising:
- multiplying the Cb coordinate of each pixel by a Cb enhancement factor;
- multiplying the Cr coordinate of each pixel by a Cr enhancement factor;
- wherein each of the Cb and Cr enhancement factors have a no-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade not to be enhanced;
- and
- wherein each of the Cb and Cr enhancement factors have a full-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade to be enhanced, the full-enhancement value comprising at last one of:
- an exposure index (EI) auxiliary enhancement factor, the EI auxiliary enhancement factor being a function of an exposure index of the digital image,
- a color temperature (D) auxiliary enhancement factor, the D auxiliary enhancement factor being a function of a color temperature of the digital image, or
- a Y auxiliary enhancement factor, the Y auxiliary enhancement factor being a function of the Y coordinate of a pixel P in the digital image.
An apparatus for evaluating and enhancing the color of pixels in a digital image, each pixel having associated Y-Cb-Cr coordinates, the apparatus comprising:
- a multiplier for multiplying the Cb coordinate of each pixel by a Cb enhancement factor;
- and
- a multiplier for multiplying the Cr coordinate of each pixel by a Cr enhancement factor;
- wherein each of the Cb and Cr enhancement factors have a no-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade not to be enhanced;
- and
- wherein each of the Cb and Cr enhancement factors have a full-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade to be enhanced, and wherein the full-enhancement value is selected from at least one of:
- an exposure index (EI) auxiliary enhancement factor, the EI auxiliary enhancement factor being a function of an exposure index of the digital image,
- a color temperature (D) auxiliary enhancement factor, the D auxiliary enhancement factor being a function of a color temperature of the digital image, or
- a Y auxiliary enhancement factor, the Y auxiliary enhancement factor being a function of the Y coordinate of a pixel P in the digital image.
An apparatus for evaluating and enhancing the color of pixels in a digital image, each pixel having associated Y-Cb-Cr coordinates, the apparatus comprising:
- means for enhancing the Cb coordinate of each pixel by a Cb enhancement factor;
- means for enhancing the Cr coordinate of each pixel by a Cr enhancement factor, wherein the Cb enhancement factor and the Cr enhancement factor are different;
- wherein each of the Cb and Cr enhancement factors have a full-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade to be enhanced, and wherein the full-enhancement value is selected from at least one of:
- an exposure index (EI) auxiliary enhancement factor, the EI auxiliary enhancement factor being a function of an exposure index of the digital image,
- a color temperature (D) auxiliary enhancement factor, the D auxiliary enhancement factor being a function of a color temperature of the digital image, or
- a Y auxiliary enhancement factor, the Y auxiliary enhancement factor being a function of the Y coordinate of a pixel P in the digital image.
A computer program product for evaluating and enhancing the color of pixels in a digital image, each pixel having associated Y-Cb-Cr coordinates, the product comprising:
- a non-transitory computer-readable medium comprising:
- code for causing a computer to multiply the Cb coordinate of each pixel by a Cb enhancement factor;
- and code for causing a computer to multiply the Cr coordinate of each pixel by a Cr enhancement factor;
- wherein each of the Cb and Cr enhancement factors have a no-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade not to be enhanced;
- and
- wherein each of the Cb and Cr enhancement factors have a full-enhancement value when the corresponding Cb-Cr coordinates of a pixel lie in a region corresponding to a color shade to be enhanced, the full-enhancement value comprising at least one of:
- an exposure index (EI) auxiliary enhancement factor, the EI auxiliary enhancement factor being a function of an exposure index of the digital image,
- a color temperature (D) auxiliary enhancement factor, the D auxiliary enhancement factor being a function of a color temperature of the digital image, or
- a Y auxiliary enhancement factor, the Y auxiliary enhancement factor being a function of the Y coordinate of a pixel P in the digital image.
Dependencies are inferred from the claim text.