Digital halftoning with minimum visual modulation patterns
First Claim
Patent Images
1. A method of generating a halftone image with an electronic digital computer, comprising the steps of:
- a. providing a set of minimum visual noise L×
M bit binery patterns by employing a stochastic combinatorial minimization technique and a human visual modulation transfer function (MTF) weighting function to generate a halftone bit pattern for each density level of the multi-level digital image signal, each pattern corresponding to a possible density level of a multiple level digital image signal;
b. providing a digital image having pixel values representing density levels; and
c. for each pixel value of the digital image signal, modularly selecting a portion of the binary bit pattern from the corresponding pattern of the set by addressing the bit pattern with lower significant bits of an x,y pixel address associated with each pixel, and employing the selected portion to form the halftone image.
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Abstract
A digital halftone image is produced by providing a binary bit image pattern having a minimum visual noise for each density level in an image. The patterns are produced by employing a stochastic combinatorial minimization technique and a human visual system modulation transfer function (MTF) weighting function to generate a halftone pattern for each density level of the multi-level digital image signal. A halftone image is produced by modularly addressing these patterns with each pixel value in the image.
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Citations
18 Claims
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1. A method of generating a halftone image with an electronic digital computer, comprising the steps of:
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a. providing a set of minimum visual noise L×
M bit binery patterns by employing a stochastic combinatorial minimization technique and a human visual modulation transfer function (MTF) weighting function to generate a halftone bit pattern for each density level of the multi-level digital image signal, each pattern corresponding to a possible density level of a multiple level digital image signal;b. providing a digital image having pixel values representing density levels; and c. for each pixel value of the digital image signal, modularly selecting a portion of the binary bit pattern from the corresponding pattern of the set by addressing the bit pattern with lower significant bits of an x,y pixel address associated with each pixel, and employing the selected portion to form the halftone image. - View Dependent Claims (2, 3, 4, 11, 12, 13, 14, 15, 16)
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5. A method of generating a halftone image with an electronic digital computer, comprising the steps of:
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a. providing a set of minimum visual noise L×
M bit binary patterns, each pattern corresponding to a possible density level of a multiple level digital image signal;b. providing a digital image having pixel values representing density levels; and c. for a given pixel value of the digital image signal, (1) modularly selecting a future portion of an N×
N neighborhood of binary values from the corresponding binary bit pattern by addressing the bit pattern with lower significant bits of an x,y pixel address associated with each pixel,(2) combining the future portion of selected binary values with a past portion of an N×
N neighborhood of previously determined binary bits to form a combined neighborhood of binary bits,(3) applying a visual blur function to the combined neighborhood of binary bits to produce a perceived output value, (4) repeating steps (1) through (3) for a plurality of neighboring pixel values to produce a plurality of estimated perceived output values, (5) computing the difference between the respective estimated perceived output values and the given pixel value and neighboring pixel values to form error values and determining the minimum error value, and (6) generating the halftone image by placing the binary bit pattern from the minimum visual noise pattern corresponding to the pixel value associated with the minimum error value computed in step 5 at each corresponding pixel location. - View Dependent Claims (6, 7, 8, 9)
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10. A method of generating a halftone image with an electronic digital computer, comprising the steps of:
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a. providing a set of minimum visual noise L×
M bit binary patterns by employing a stochastic combinatorial minimization technique and a human visual system modulation transfer function (MTF) weighting function to generate a halftone bit pattern for each density level of the multi-level digital image signal, each pattern corresponding to a possible density level of a multiple level digital image signal;b. providing a digital image having pixel values representing density levels; c. for successive two-dimensional blocks of pixel values in the digital image, (1) calculating the mean value of the pixels in the block, (2) modularly selecting a portion of the binary bit pattern corresponding to the mean pixel value by addressing the binary bit pattern with lower significant bits of an x,y address corresponding to the location of the two-dimensional blocks of pixel values, (3) detecting a two-dimensional slope in the pixel values across the block, (4) performing a spatial transformation on the selected portion of the bit pattern to shift the spatial position of binary values in proportion to the detected slope, and (5) employing the transformed selected portion of the bit pattern to form the halftone image. - View Dependent Claims (17, 18)
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Specification