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imapprox
Purpose
12imapprox
Approximate indexed image by one with fewer colors
Syntax
[Y,newmap] = imapprox(X,map,n)
[Y,newmap] = imapprox(X,map,tol)
Y = imapprox(X,map,newmap)
[...] = imapprox(...,dither_option)
Description
[Y,newmap] = imapprox(X,map,n) approximates the colors in the indexed
image X and associated colormap map by using minimum variance
quantization. imapprox returns indexed image Y with colormap newmap, which
has at most n colors.
[Y,newmap] = imapprox(X,map,tol) approximates the colors in X and map
through uniform quantization. newmap contains at most (floor(1/tol)+1)^3
colors. tol must be between 0 and 1.0.
Y = imapprox(X,map,newmap) approximates the colors in map by using
colormap mapping to find the colors in newmap that best match the colors in map.
Y = imapprox(...,dither_option) enables or disables dithering.
dither_option is a string that can have one of these values:
• 'dither' dithers, if necessary, to achieve better color resolution at the
expense of spatial resolution (default).
• 'nodither' maps each color in the original image to the closest color in the
new map. No dithering is performed.
Class Support
The input image X can be of class uint8, uint16, or double. The output image
Y is of class uint8 if the length of newmap is less than or equal to 256. If the
length of newmap is greater than 256, X is of class double.
Algorithm
imapprox uses rgb2ind to create a new colormap that uses fewer colors.
See Also
cmunique, dither, rgb2ind
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