/* ColorMaskedTextureBlitShader: Shader for color-keyed blitting of 2D rectangle textures.
// OpenGL program has to setup the the "color-key" value that is considered
// background color and discarded during the blit.
//
// (w)2011 by Mario Kleiner. Licensed under MIT license.
*/

#extension GL_ARB_texture_rectangle : enable

uniform sampler2DRect Image;
uniform float         epsilon;
uniform vec3          backgroundColor;

void main()
{
    /* Fetch texel color at current location: */
    vec4 texcolor = texture2DRect(Image, gl_TexCoord[0].st);

    /* If texel color matches background color key --> Discard fragment */
    if (distance(texcolor.rgb, backgroundColor) < epsilon) discard;

    /* Assign, with modulateColor applied: */
    gl_FragColor = texcolor * gl_Color;
}
