Background suppression method and apparatus
First Claim
Patent Images
1. A method of transforming an original image from a red-green-blue (RGB) color space representation to a luminance-chrominance (Lab) color space representation, comprising:
- receiving an original image in a red-green-blue color space at an analyzer of a document processing system;
converting pixels in the original image from the RGB color space to a luminance chrominance color space using an RGB to Lab converter;
determining background pixels in the original image using a background pixel determining processor, including;
comparing a luminance value (L) representation of each pixel in the Lab color space to a selectable, adjustable luminance threshold value,comparing a chrominance value (ab) representation to a predetermined chrominance threshold value for each pixel in the Lab color space for which the luminance value representation exceeds the luminance threshold value; and
identifying pixels having chrominance value representations less than the predetermined chrominance threshold value as background pixels; and
variably adjusting the chrominance value (ab) representation of pixels of the original image for each background pixel in the Lab color space having a chrominance value representation in a neutral chrominance range defined by a start chrominance value less than a neutral chrominance value and an end chrominance value greater than the neutral chrominance value using a background pixel adjusting processor, the variable adjusting based at least in part on a functional relationship of the chrominance value representation to a prespecified chrominance adjustment table associated with the neutral chrominance range.
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Abstract
An original image is received in a red-green-blue color space. Pixels in the original image are converted to a luminance-chrominance color space. Background pixels in the original image are determined by comparing a luminance value of each pixel to a selectable luminance threshold, and comparing chrominance value of each pixel to a predetermined chrominance threshold. Chrominance values of the background pixels in each chrominance channel are adjusted.
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Citations
19 Claims
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1. A method of transforming an original image from a red-green-blue (RGB) color space representation to a luminance-chrominance (Lab) color space representation, comprising:
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receiving an original image in a red-green-blue color space at an analyzer of a document processing system; converting pixels in the original image from the RGB color space to a luminance chrominance color space using an RGB to Lab converter; determining background pixels in the original image using a background pixel determining processor, including; comparing a luminance value (L) representation of each pixel in the Lab color space to a selectable, adjustable luminance threshold value, comparing a chrominance value (ab) representation to a predetermined chrominance threshold value for each pixel in the Lab color space for which the luminance value representation exceeds the luminance threshold value; and identifying pixels having chrominance value representations less than the predetermined chrominance threshold value as background pixels; and variably adjusting the chrominance value (ab) representation of pixels of the original image for each background pixel in the Lab color space having a chrominance value representation in a neutral chrominance range defined by a start chrominance value less than a neutral chrominance value and an end chrominance value greater than the neutral chrominance value using a background pixel adjusting processor, the variable adjusting based at least in part on a functional relationship of the chrominance value representation to a prespecified chrominance adjustment table associated with the neutral chrominance range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A document processing system comprising:
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a device for producing a red-green-blue color space representation of an original image; a red-green-blue color space to luminance-chrominance color space converter for converting red-green-blue pixel values for the original image in the red-green-blue (RGB) color space into corresponding luminance-chrominance pixel values in the luminance-chrominance (Lab) color space; a white pixel determining processor for determining background pixels in the original image by comparing a luminance value (L) representation of each pixel in the Lab color space to a selectable, adjustable luminance threshold value, and comparing a chrominance value (ab) representation to a predetermined chrominance threshold value for each pixel in the Lab color space for which the luminance value representation exceeds the luminance threshold value to identify pixels having chrominance value representations less than the predetermined chrominance threshold value as background pixels; a chrominance value adjusting processor for variably adjusting the chrominance value (ab) representation of pixels of the original image for each background pixel in the Lab color space having a chrominance value in a neutral chrominance range defined by a start chrominance value less than a neutral chrominance value and an end chrominance value greater than the neutral chrominance value based at least in part on a functional relationship of the chrominance value representation to the neutral chrominance range; and a chrominance adjustment table associated with the neutral chrominance range for adjusting the chrominance value representation of background pixels in the neutral chrominance range based on the chrominance adjustment table. - View Dependent Claims (14, 15, 16)
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17. A method of transforming an original image from a red-green-blue (RGB) color space representation to a luminance-chrominance (Lab) color space representation, comprising:
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receiving an original image in a red-green-blue color space at an analyzer of a document processing system; converting pixels in the original image from the RGB color space to a luminance-chrominance color space using an RGB to Lab converter; determining background pixels in the original image using a background pixel determining processor, including; comparing a luminance value (L) representation of each pixel in the Lab color space to a first luminance threshold, comparing a chrominance value (ab) representation to a predetermined chrominance threshold for each pixel in the Lab color space for which the luminance value representation exceeds the first luminance threshold; and identifying pixels having chrominance value representations less than the predetermined chrominance threshold as background pixels; and variably adjusting the chrominance value (ab) representation of pixels of the original image for each background pixel in the Lab color space having a chrominance value representation in a neutral chrominance range using a background pixel adjusting processor based at least in part on a relationship of the pixel chrominance value representation to a prespecified chrominance adjustment table associated with the neutral chrominance range. - View Dependent Claims (18, 19)
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Specification