I have a texture .
the texture has 3 colors [gray black white]
I want to convert the texture into 2 colors texture [black white]
that is to say , gray colors should be turned to black color.
if I use pixel shader, that is easy.
I make billboard plane and settexture [3 colors texture]
and draw billboard using pixel shader
[ ps code , if color gray, then set out color to black].
and then capture the rendering result [ back buffer or rendertosurface
but I use only fixed pipeline.
that is , if I use color op, alpha op in SetTextureStageState.
how can I get 2 color texture from 3 color texture.
that is to say,
I want to know how to set color op to achieve it.