Browse Prior Art Database

Combined Image Enlargement and Dithering

IP.com Disclosure Number: IPCOM000103652D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Feig, E: AUTHOR [+3]

Abstract

Disclosed is an algorithm for simultaneously enlarging, palettizing and dithering an image.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Combined Image Enlargement and Dithering

       Disclosed is an algorithm for simultaneously enlarging,
palettizing and dithering an image.

      This shows that the image is to be expanded by a factor of M
horizontally and N vertically.  Corresponding to every pixel in the
original image are 3 basic color values, v1, v2, v3, typically for
red-green-blue or Y-U-V (luminance and 2 chrominance components),
which range in value from 0 to Vi (or from any Wi to Vi-Wi).  The
enlarged image will have its (i,j)-th pixel values replaced by an M x
N matrix of indices for palette values.  These may be obtained as
follows: first form three M x N matrices S1, S2, S3 whose entries are
all, respectively, v1, v2, v3.  Subject each Si to a dither
distortion using any standard set of dither patterns and obtain
matrices T1, T2, T3, respectively.  If Di is the dither pattern for
the i-th basic color, then Ti = Si + Di.  Fix a set of quantized
values in each of the 3 basic colors, and quantize each entry in Ti
relative to these values (i.e., replace each entry in Ti by its
closest quantized value) yielding matrices Qi.  For each i, there
will be Ni distinct matrices Qi.  One then forms a table, indexed by
N1, N2, N3, of all possible distinct dither patterns, where the
dithered-palettized patterns are obtained by doing a pointwise
palette lookup on each entry of each M x N matrix.

      One creates mappings Fi, corresponding to each basic color i,
which map the integers be...