Tone dependent error diffusion

A tone dependent error diffusion halftoning system uses tone dependent thresholds and error weightings that are optimized by minimizing a model based cost function. An upper and lower threshold are used to compare with the modified pixel value. If the modified pixel value is greater than the upper t...

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Bibliographic Details
Main Authors LI, PINGSHAN, ALLEBACH, JAN P
Format Patent
LanguageEnglish
French
German
Published 08.11.2000
Edition7
Subjects
CALCULATING
COMPUTING
COUNTING
ELECTRIC COMMUNICATION TECHNIQUE
ELECTRICITY
IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
PHYSICS
PICTORIAL COMMUNICATION, e.g. TELEVISION
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Summary:A tone dependent error diffusion halftoning system uses tone dependent thresholds and error weightings that are optimized by minimizing a model based cost function. An upper and lower threshold are used to compare with the modified pixel value. If the modified pixel value is greater than the upper threshold, a dot is printed, if less than the lower threshold, no dot is printed, and if between, a binary bitmap is used to determine whether a dot should be printed. For each midtone threshold level, a halftone image is generated by a direct binary search method and an error diffusion method. The magnitudes of the fast Fourier transforms, of the halftone images are compared using a visual cost function and the thresholds and error weightings are altered to minimize the cost function. For highlight and shadow tone levels, a filtered halftone image from an error diffusion system is compared to the continuous tone image after filtering the image via a human visual system model. Again by minimizing the cost function, the thresholds and error weightings are optimized.
Bibliography:Application Number: EP20000303632