Method and apparatus for vivid color correction in binary printing devices
AssigneeSeiko Epson Corporation
InventorJoseph S. Shu
Life of this patent
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Abstract
A vivid color correction technique eliminates artifacts from a predetermined tonal area of a halftone image to thereby improve the color vividness of that image. According to this technique, pixel tonal values associated with input colors are initially examined to determine a maximum color value. After error diffusion halftoning, the resulting binary pixel values are collectively processed to generate inter-color information for comparison with a selected harmonic color cluster. If the inter-color information specifies a color that does not match one of the colors of the selected harmonic cluster, the inter-color information is "corrected" to reflect an acceptable output color.
Claims21
A method for improving the color vividness of a halftone image generated from a plurality of streams of continuous-tone input pixels, each stream comprising pixels having values of a specific tonal color, the method comprising the steps of:
- converting a first input pixel of each stream into a first binary pixel value;
- collectively processing said first binary pixel value from each stream to generate inter-color information;
- providing said inter-color information to an output buffer for printing as processed halftone color pixel values that improve the color vividness of the halftone image;
- and
- determining a maximum tonal color value from among said first input pixels of each stream,
- wherein said collectively processing step comprises the step of comparing said inter-color information with color values of a selected harmonic color cluster.
A method for improving the color vividness of a halftone image generated from a plurality of streams of continuous-tone input pixels, each stream comprising pixels having values of a specific tonal color, the method comprising the steps of:
- converting a first input pixel of each stream into a first binary pixel value;
- collectively processing said first binary pixel value from each stream to generate inter-color information;
- and
- providing said inter-color information to an output buffer for printing as processed halftone color pixel values that improve the color vividness of the halftone image,
- wherein said converting step comprises the steps of:
- iteratively comparing the tonal value of each first input pixel with a threshold value;
- selecting a binary pixel value based on the comparison;
- electronically storing an error value defining the difference between the first input pixel value and the threshold value;
- and
- diffusing the error value among neighboring pixels of each stream.
An apparatus for improving the color vividness of a halftone image generated from a plurality of streams of continuous-tone input pixels, each stream comprising pixels having values of a specific tonal color, the apparatus comprising:
- means for converting a first input pixel of each stream into a first binary pixel value;
- means for collectively processing said first binary pixel value from each stream to generate inter-color information;
- means for providing said inter-color information to an output buffer for printing as processed halftone color pixel values that improve the color vividness of the halftone image;
- and
- means for determining a maximum tonal color value from among said first input pixels of each stream,
- wherein said collectively processing means comprises a color correction circuit for comparing said inter-color information with color values of a selected harmonic color cluster.
An apparatus for improving the color vividness of a halftone image generated from a plurality of streams of continuous-tone input pixels, each stream comprising pixels having values of a specific tonal color, the apparatus comprising:
- means for converting a first input pixel of each stream into a first binary pixel value;
- means for collectively processing said first binary pixel value from each stream to generate inter-color information;
- means for providing said inter-color information to an output buffer for printing as processed halftone color pixel values that improve the color vividness of the halftone image;
- and
- an input buffer for storing the tonal pixel values of an immediately previous series of pixels, and wherein the previously processed pixels are selected from the buffer.
A computer system comprising:
- a memory for storing data and programs;
- a central processing unit responsive to programs stored in the memory for controlling and coordinating the operation of the computer system;
- digitizing means responsive to a continuous-tone image for generating a stream of electronically encoded pixel values, each representing a grayscale value of a portion of the continuous-tone image;
- an input buffer responsive to the stream of electronically encoded pixel values for storing the electronically encoded pixel values in a plurality of linear segments, each linear segment comprising pixel values that represent contiguous portions of the continuous-tone image;
- a pixel detection and control circuit for determining a maximum grayscale value of the electronically encoded pixels;
- error diffusion halftoning means for quantizing the grayscale values into a halftone pattern, and for generating quantization errors adapted for diffusion among neighboring encoded pixel values of the stream;
- a color correction circuit for generating inter-color information from said quantized grayscale values and for correcting said inter-color information to generate predetermined color values when said inter-color information does not match a color value of a selected harmonic color cluster, said selected harmonic color cluster being selected in response to said determined maximum grayscale value;
- and
- a printer responsive to said predetermined color values for printing the halftone pattern of monochrome dots on a print medium to generate a halftone image.
Dependencies are inferred from the claim text.