Tone correction method using a blending mask
First Claim
1. A digital imaging system, comprising:
- an image sensor comprising a two-dimensional array of pixel elements, said image sensor outputting digital signals as pixel data representing an image of a scene;
a frame buffer, in communication with said image sensor, coupled to store said pixel data provided by said image sensor; and
a tone correction circuit coupled to receive pixel data from said frame buffer and compute tone corrected pixel data using one or more tone correction curves,wherein said tone correction circuit computes tone corrected pixel data for a first pixel by generating a pixel mask for an m×
n neighborhood of pixels surrounding said first pixel, the pixel mask classifying the m×
n neighborhood of pixels to a first value and a second value according to one or more threshold values, applying a blending mask of weight factors to said pixel mask and computing a selector value based on said pixel mask and weight factors associated with said blending mask, said selector value being used to derive a first tone correction curve for use to compute said tone corrected pixel data for said first pixel; and
wherein the selector value is computed by counting the number of first values in the pixel mask corresponding to a respective weight factor in the blending mask, multiplying each count value by the respective weight factor, and summing the count-weight factor products to obtain the selector value.
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Abstract
A digital imaging system includes an image sensor, a frame buffer and a tone correction circuit. The tone correction circuit computes tone corrected pixel data using one or more tone correction curves. In operation, tone corrected pixel data for a first pixel is computed by generating a pixel mask for an m×n neighborhood of pixels surrounding the first pixel, applying a blending mask of weight factors to the pixel mask and computing a selector value based on the pixel mask and weight factors associated with the blending mask. The selector value is used to derive a first tone correction curve for use to compute the tone corrected pixel data for the first pixel. The first tone correction curve can be selected from the multiple tone correction curves based on the selector value or it can be derived by blending multiple tone correction curves based on the selector value.
51 Citations
14 Claims
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1. A digital imaging system, comprising:
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an image sensor comprising a two-dimensional array of pixel elements, said image sensor outputting digital signals as pixel data representing an image of a scene; a frame buffer, in communication with said image sensor, coupled to store said pixel data provided by said image sensor; and a tone correction circuit coupled to receive pixel data from said frame buffer and compute tone corrected pixel data using one or more tone correction curves, wherein said tone correction circuit computes tone corrected pixel data for a first pixel by generating a pixel mask for an m×
n neighborhood of pixels surrounding said first pixel, the pixel mask classifying the m×
n neighborhood of pixels to a first value and a second value according to one or more threshold values, applying a blending mask of weight factors to said pixel mask and computing a selector value based on said pixel mask and weight factors associated with said blending mask, said selector value being used to derive a first tone correction curve for use to compute said tone corrected pixel data for said first pixel; andwherein the selector value is computed by counting the number of first values in the pixel mask corresponding to a respective weight factor in the blending mask, multiplying each count value by the respective weight factor, and summing the count-weight factor products to obtain the selector value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for providing tone correction to an image, comprising:
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generating digital pixel data representative of an image of a scene using an image sensor, said image sensor comprising a two-dimensional array of pixel elements; storing said digital pixel data in a frame buffer; for a first pixel in said image, selecting an m×
n neighborhood of pixels surrounding said first pixel;generating a pixel mask for said m×
n neighborhood of pixels, said pixel mask including a first value to indicate a pixel in said m×
n neighborhood of pixels having a pixel value greater than a threshold value and said pixel mask including a second value to indicate a pixel in said m×
n neighborhood of pixels having a pixel value smaller than said threshold value;providing a blending mask including weight factors; applying said blending mask to said pixel mask; computing a selector value based on said pixel mask and weight factors associated with said blending mask, wherein computing the selector value comprises;
counting the number of first values in the pixel mask corresponding to a respective weight factor in the blending mask, multiplying each count value by the respective weight factor, and summing the count-weight factor products to obtain the selector value;providing a plurality of tone correction curves; and deriving a first tone correction curve from said plurality of tone correction curves based on said selector value for use to compute said tone corrected pixel data for said first pixel. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification