Method and apparatus for accurately rendering half-bitted image pixels
First Claim
1. A method for accurately rendering half-bitted pixels upon increasing the resolution of a binary input image to be printed by an electronic printing system, comprising the steps of:
- storing a portion of the binary input image in a scanline buffer memory;
selecting a central pixel within the binary input image;
determining the binary state of the central pixel and of a plurality of pixels neighboring the central pixel;
comparing the binary pixel states of the central pixel and the neighboring pixels to associated pixel states in a predefined template;
detecting when a match occurs between the central and neighboring pixel states and the predefined template to identify an occurrence of a half-bitted central pixel;
defining, upon detection of a match, a multi-bit digital signal as a value uniquely associated with the predefined template identified by the match; and
converting the multi-bit digital signal into a resolution enhanced output pixel suitable for printing by the electronic printing system wherein the resolution enhanced output pixel will not result in a half-bitted output when printed by the electronic printing system.
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Abstract
A method and apparatus for identifying regions within a first binary image where half-bitting may be present, converting those regions to a multiple-bit/pixel representation so as to accurately represent the image density and the intended edge structure for the region, and further generating an enhanced resolution representation of the region in either a second binary image, wherein the second binary image has a spatial resolution greater than the first image, or a multiple-bit per pixel (gray) image at the same resolution as the input image so as to enable an improved rendering of the first binary image.
36 Citations
17 Claims
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1. A method for accurately rendering half-bitted pixels upon increasing the resolution of a binary input image to be printed by an electronic printing system, comprising the steps of:
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storing a portion of the binary input image in a scanline buffer memory; selecting a central pixel within the binary input image; determining the binary state of the central pixel and of a plurality of pixels neighboring the central pixel; comparing the binary pixel states of the central pixel and the neighboring pixels to associated pixel states in a predefined template; detecting when a match occurs between the central and neighboring pixel states and the predefined template to identify an occurrence of a half-bitted central pixel; defining, upon detection of a match, a multi-bit digital signal as a value uniquely associated with the predefined template identified by the match; and converting the multi-bit digital signal into a resolution enhanced output pixel suitable for printing by the electronic printing system wherein the resolution enhanced output pixel will not result in a half-bitted output when printed by the electronic printing system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for improving the appearance of a binary input image to be printed by an electronic printing system, the binary input image containing a half-bitted region therein, comprising the steps of:
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storing a portion of the binary input image in scanline buffer memory; identifying the region of half-bitted image pixels within the binary input image by comparing the binary states of image pixels stored in the scanline buffer memory to a plurality of predetermined templates, wherein the templates represent binary bitmap patterns characteristically found in half-bitted regions of an image; identifying for each match between the stored image pixel states and a predetermined template, the stored pixel corresponding to the target pixel of the template as a half-bitted image pixel; generating a plurality of multi-bit digital signals to represent image pixels within the half-bitted region; and converting each multi-bit digital signal into a resolution enhanced output pixel suitable for printing by the electronic printing system. - View Dependent Claims (10, 11, 12, 13)
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14. An apparatus for accurately rendering half-bitted pixels upon increasing the resolution of a binary input image to be printed by an electronic printing system, including:
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scanline buffer memory for storing a portion of the binary input image; target pixel selection means, operating on the stored portion of the binary input image, for selecting a central pixel within the binary input image; template matching means for comparing the binary pixel state of the central pixel and a plurality of pixels neighboring the central pixel to a predetermined template pattern to identify an occurrence of a half-bitted central pixel, so as to determine a unique multi-bit digital signal which represents a desired output density for the central pixel; and a video signal generator for converting the multi-bit digital signal into at least one output pixel suitable for printing by the electronic printing system wherein the resolution enhanced output pixel will not result in a half-bitted output when printed by the electronic printing system. - View Dependent Claims (15, 16, 17)
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Specification