//
// Fragment shader for bilinear filternig
//
// Copyright (c) 2007 by Roman Marchenko & Andrey Budko
//

void DoFiltering()
{
  float pixel_c  = rgbaBias + rgbaScale * texture2D(tex, texCoord).r;
  float pixel_r  = rgbaBias + rgbaScale * texture2D(tex, texCoord.xy + vec2(texelSizes.x, 0)).r;
  float pixel_b  = rgbaBias + rgbaScale * texture2D(tex, texCoord.xy + vec2(0, texelSizes.y)).r;
  float pixel_rb = rgbaBias + rgbaScale * texture2D(tex, texCoord.xy + texelSizes).r;

  vec4 texel_c  = texture2D(texColormap, vec2(pixel_c,  cm));
  vec4 texel_r  = texture2D(texColormap, vec2(pixel_r,  cm));
  vec4 texel_b  = texture2D(texColormap, vec2(pixel_b,  cm));
  vec4 texel_rb = texture2D(texColormap, vec2(pixel_rb, cm));

  vec2 lerpAmounts = fract(texCoord * texSizes);
  final = mix(
    mix(texel_c, texel_r,  lerpAmounts.x),
    mix(texel_b, texel_rb, lerpAmounts.x),
    lerpAmounts.y);
}