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| XOR drawing mode |
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crexalbo
Member #15,035
April 2013
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I am looking to enable XOR drawing mode with Allegro 5. I have found the al_set_blender function, but i do not see any sort of XOR drawing mode it can use; only ADD, SRC_MINUS_DEST, and DEST_MINUS_SRC. Is there a way to use these existing drawing modes to implement XOR? My ultimate goal is i want to negate pixels in a certain area of the screen. So, for example, if the pixel's color is originally <0.2, 0.9, 0.6>, then i want its new color after the drawing operation to be <0.8, 0.1, 0.4>. |
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Arthur Kalliokoski
Second in Command
February 2005
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If you're using OpenGL, it looks like glEnable(GL_BLEND); glBlendFunc(GL_ONE_MINUS_DST_COLOR, GL_ZERO); would work, otherwise I'd think you have to use shaders. They all watch too much MSNBC... they get ideas. |
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SiegeLord
Member #7,827
October 2006
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I imagine doing something like this would work al_set_blender(ALLEGRO_ADD, ALLEGRO_INVERSE_DEST_COLOR, ALLEGRO_ZERO) in conjunction with something white being drawn. "For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18 |
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