Method and apparatus for background adjustment in color reproduction devices
AssigneeSharp Laboratories of America, Inc.
InventorsXiao-Fan Feng, Jon Matthew Speigle, James Charles Dalrymple, James Zhixin Chang
Life of this patent
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Abstract
A method for background adjustment. A background lightness level in an original image is estimated. Pixels are then converted to a luminance-chrominance color space. Pixels have lightness levels equal to the background lightness level are mapped to a value corresponding to white as background pixels. Chroma values for the background pixels are compared to a threshold ad adjusted as needed, either by adjusting the lightness value or by removing the chrominance values. The luminance-chrominance data is then converted to output space.
Claims19
A method for background adjustment, the method comprising:
- a) estimating a background lightness level in an original image;
- b) converting pixels in the original image to a luminance-chrominance color space, wherein pixels having lightness levels substantially equal to the background lightness level are mapped as background pixels such that their lightness values are set substantially equal to a value corresponding to white;
- c) comparing chroma values for the background pixels to at least one threshold;
- d) adjusting lightness levels for any background pixels having chroma values above a first threshold to a new lightness level, producing lightness adjusted pixels;
- e) removing chroma from any background pixels having chroma values below a second threshold, producing color adjusted pixels;
- and
- f) converting to a color space of an output device, wherein conversion is performed on all pixels including any lightness adjusted pixels and color-adjusted pixels.
A computer-readable medium including software code that, when executed, results in:
- a) estimation of a background lightness level in an original image;
- b) conversion of pixels in the original image to luminance-chrominance color space, wherein pixels having lightness levels substantially equal to the background lightness level are mapped as background pixels with their lightness values are set substantially equal to a value corresponding to white;
- c) comparison of chroma values for the background pixels to a threshold;
- d) adjustment of the lightness level for any background pixels having chroma values above the threshold to a new lightness level, producing lightness adjusted pixels;
- e) removal of chroma from any background pixels having chroma values below the threshold, producing color adjusted pixels;
- and
- f) conversion to an output space, wherein conversion is performed on all pixels including any lightness adjusted pixels and color adjusted pixels.
A color reproduction device, comprising:
- a) a scanning module operable to scan a color original and produce input data representative of the color original;
- b) a background suppression module operable to:
- i) determine a background lightness level;
- and
- ii) map pixels of input data to luminance-chrominance color space such that pixels having a lightness level substantially equal to the background lightness level are mapped as background pixels having a lightness value corresponding to white;
- c) a chroma adjustment module, operable to:
- i) determine if chroma values for the background pixels are above a threshold;
- ii) adjust any background pixels having a chroma value above the threshold to a lightness level different from the lightness corresponding to white;
- and
- iii) remove chroma from any background pixels having a chroma value below the threshold;
- and
- d) an output conversion module, operable to convert all pixels in the luminance-chrominance color space to an output space.
Dependencies are inferred from the claim text.