Posted by William Gill on 08/30/07 13:20

I have found a couple of sites that allow a visitor to upload an image
and the site returns either the "average color", or a palette of colors.
Several of them use PHP to accomplish this. I have requested the source
code, but have not gotten a response (even though one site states
"source code available on request"). It is obvious that they read the
colors of each pixel and them manipulate that data. I would like to be
able to do something similar.

I'm not very familiar with the PHP image functions, but have been able
to figure out how to read pixel color on indexed color images, but not
on jpegs. The best I can do now is convert a jpeg to a 256 indexed
color image, and then read pixel color. Unfortunately too much of the
original data gets lost.

Does anyone know how to determine the color of jpeg pixels, or can you
point me to a good tutorial on PHP image functions.

For what it's worth, one of the things I want to do is determine the
distribution of each color (i.e. 345 pixels of rgb1, 2436 pixels of
rgb2, etc.), and possibly manipulate the image by removing and/or
replacing any given color.

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