Method and apparatus for tonal correction in binary printing devices by predistortion of image data utilizing ink reduction processing
First Claim
Patent Images
1. A method of printing comprising:
- a. obtaining a series of pixel data corresponding to a linear segment of source image;
b. selecting every other one of the pixel data obtained in step a;
c. filtering the pixel data selected in step b in accordance with a filter function;
d. processing the pixel data filtered in step c into a halftone pattern which, when printed, exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions; and
e. printing a series of dots in accordance with the halftone pattern onto a recording medium,wherein the filter function is defined such when the halftone pattern is printed, the printed pattern exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.
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Abstract
An image preprocessing method and apparatus processes image data line-by-line using an error diffusion or dithering process to generate a halftoned image in which the radius of a dot representing a pixel is /dpi≦r≦√2/dpi. The method and apparatus selectively performs the halftone process on every other pixel to reduce in consumption and computation time while maintaining a high resolution.
38 Citations
27 Claims
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1. A method of printing comprising:
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a. obtaining a series of pixel data corresponding to a linear segment of source image; b. selecting every other one of the pixel data obtained in step a; c. filtering the pixel data selected in step b in accordance with a filter function; d. processing the pixel data filtered in step c into a halftone pattern which, when printed, exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions; and e. printing a series of dots in accordance with the halftone pattern onto a recording medium, wherein the filter function is defined such when the halftone pattern is printed, the printed pattern exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. Printing apparatus comprising:
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a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a filter for modifying the selected data in accordance with a filter function; d. a halftone engine for processing the modified data into a halftone pattern; and e. means for applying dots of ink or toner to a recording medium forming an output in accordance with the halftone pattern, wherein the filter function is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. Printing apparatus comprising:
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a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a halftone engine having a filter characteristic for processing the selected data into a raster pattern; and d. means for applying dots of ink or toner to a recording medium in accordance with the halftone pattern, wherein the filter characteristics is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions. - View Dependent Claims (25, 26, 27)
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Specification