Method for accurate real-time compensation for changing illumination spectra in digital video cameras
AssigneeArecont Vision, LLC.
InventorMichael Kaplinsky
Life of this patent
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Abstract
A method for determining a correction for a spectra of scene illumination based on analysis of color content of a video image, in which average image colors are obtained by considering only those image pixels that have significantly different color from any of its neighboring pixels resulting in selection of only those pixels that lay on the boundaries of monochrome image segments, while avoiding their inner areas. Therefore, the white balance method is not only tolerant to the presence of large non-gray monochrome areas in the image, but also avoids the image areas that have small chrominance values and appear to be gray due to specific illumination spectra, while not actually corresponding to the grey areas of the scene.
Claims12
A method of determining a correction for a spectra of scene illumination based on analysis of color content of a video image, the method comprising:
- electronically considering two pixels at a time to determine pairs of neighboring image pixels that substantially differ in color from each other;
- electronically evaluating overall sums of color components of the image by adding values of each color component of the pixels of said pixel pairs;
- electronically determining an average image luminance by adding together luminance values of the pixels of said pixel pairs;
- electronically computing gain adjustments for said color components of the image in a manner that said sums of color components of the image are equalized and said average image luminance does not change;
- and
- electronically applying said computed gain adjustments to said color components of all image pixels, wherein
- said electronically determining is performed by sequentially inspecting pixel pairs along a scan direction of the image, wherein only pixel pairs comprising pixels of the same image line and having N pixels between them are considered for determining pairs of neighboring image pixels, and wherein N is an integer value from 0 to a length of an image line minus two.
A method of determining a correction for a spectra of scene illumination based on analysis of color content of a video image, the method comprising:
- electronically considering two pixels at a time to determine pairs of neighboring image pixels that substantially differ in color from each other;
- electronically evaluating overall sums of color components of the image by adding values of each color component of the pixels of said pixel pairs;
- electronically determining an average image luminance by adding together luminance values of the pixels of said pixel pairs;
- electronically computing gain adjustments for said color components of the image in a manner that said sums of color components of the image are equalized and said average image luminance does not change;
- and
- electronically applying said computed gain adjustments to said color components of all image pixels,
- wherein said computing gain adjustments adjusting comprises the steps of:
- computing ratios of blue and red color gains currently applied to the image to sums of blue and red color components of the image;
- and
- obtaining new color gains by multiplying said ratios by a value of said image luminance.
A method of determining a correction for a spectra of scene illumination based on analysis of color content of a video image, the method comprising:
- electronically considering two pixels at a time to determine pairs of neighboring image pixels that substantially differ in color from each other;
- electronically identifying substantially gray image pixels, wherein each of said pixels having red, green and blue components of similar magnitude;
- electronically evaluating overall sums of color components of the image by adding values of each color component of pixels of said pixel pairs and values of each color component of all said substantially gray pixels;
- electronically determining image luminance by adding together luminance values of the pixels of said pixel pairs and luminance values of all said substantially gray pixels;
- electronically computing gain adjustments for said color components of the image in a manner that said sums of color components of the image are equalized and said average image luminance does not change;
- and
- electronically applying said computed gain adjustments to said color components of all image pixels, wherein
- said electronically identifying of said substantially gray pixels and said adding of values of said substantially gray pixels are performed only when the image colors have been determined to be substantially balanced.
A method of determining a correction for a spectra of scene illumination based on analysis of color content of a video image, the method comprising:
- electronically considering two pixels at a time to determine pairs of neighboring image pixels that substantially differ in color from each other;
- electronically identifying substantially gray image pixels, wherein each of said pixels having red, green and blue components of similar magnitude;
- electronically evaluating overall sums of color components of the image by adding values of each color component of pixels of said pixel pairs and values of each color component of all said substantially gray pixels;
- electronically determining image luminance by adding together luminance values of the pixels of said pixel pairs and luminance values of all said substantially gray pixels;
- electronically computing gain adjustments for said color components of the image in a manner that said sums of color components of the image are equalized and said average image luminance does not change;
- and
- electronically applying said computed gain adjustments to said color components of all image pixels, wherein said electronically computing gain adjustments comprises the steps of:
- electronically computing ratios of blue and red color gains currently applied to the image to sums of blue and red color components of the image;
- and
- obtaining new color gains by multiplying said ratios by a value of said image luminance.
Dependencies are inferred from the claim text.