From: Tim Hunter <rmagick@...>
Date: 2008-04-10T03:50:37+09:00
Subject: Re: RMagick and Collision Mask

Diego Bernardes wrote:
> Im trying to make a perfect pixel collision in a game and im gonna use a
> collision mask to do this, the physics its with chipmunk and i need a
> polygon to do it, my idea is, read the image pixel per pixel and store
> in a matrix the x and y of the black pixels, later with this matrix i
> can create a poligon just geting the first and last element from the
> column in each line of the matrix.
> 
> The problem is the RMagick, i know how to read the image pixel per pixel
> but dont know how to compare the color to get only the black pixels
> 
> Someone can help me?
> 
> thx :)

black = Magick::Pixel.from_color("black")
p == black  # true if the pixel p is black.

If you want to include "almost black" pixels then use 
Magick::Pixel#fcmp: 
http://www.imagemagick.org/RMagick/doc/struct.html#Pixel.

If you have any other questions about RMagick you can always contact me 
at rmagick@rubyforge.org, or post your question on the Help Forum for 
the RMagick project on RubyForge: 
http://rubyforge.org/forum/?group_id=12.
-- 
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