uniform sampler2D OGL2Texture;

// The inverse of the texture dimensions along X and Y
uniform vec4 OGL2InvSize;

const mat3 RGBtoYIQ = mat3(0.299, 0.596, 0.212, 
                           0.587,-0.275,-0.523, 
                           0.114,-0.321, 0.311);

const mat3 YIQtoRGB = mat3(1.0, 1.0, 1.0,
                           0.95568806036115671171,-0.27158179694405859326,-1.1081773266826619523,
                           0.61985809445637075388,-0.64687381613840131330, 1.7050645599191817149);

const vec3 val00 = vec3( 1.2, 1.2, 1.2);

void main() {
  // The parameters are hardcoded for now, but could be
  // made into uniforms to control fromt he program.
  float FXAA_SPAN_MAX = 8.0;
  float FXAA_REDUCE_MUL = 1.0/8.0;
  float FXAA_REDUCE_MIN = (1.0/128.0);

  vec3 rgbNW = texture2D(OGL2Texture, gl_TexCoord[0].xy + (vec2(-1.0, -1.0) * OGL2InvSize)).xyz;
  vec3 rgbNE = texture2D(OGL2Texture, gl_TexCoord[0].xy + (vec2(+1.0, -1.0) * OGL2InvSize)).xyz;
  vec3 rgbSW = texture2D(OGL2Texture, gl_TexCoord[0].xy + (vec2(-1.0, +1.0) * OGL2InvSize)).xyz;
  vec3 rgbSE = texture2D(OGL2Texture, gl_TexCoord[0].xy + (vec2(+1.0, +1.0) * OGL2InvSize)).xyz;
  vec3 rgbM  = texture2D(OGL2Texture, gl_TexCoord[0].xy).xyz;
	
  vec3 luma = vec3(0.299, 0.587, 0.114);
  float lumaNW = dot(rgbNW, luma);
  float lumaNE = dot(rgbNE, luma);
  float lumaSW = dot(rgbSW, luma);
  float lumaSE = dot(rgbSE, luma);
  float lumaM  = dot(rgbM,  luma);
	
  float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));
  float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));
	
  vec2 dir;
  dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));
  dir.y =  ((lumaNW + lumaSW) - (lumaNE + lumaSE));
	
  float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);
	  
  float rcpDirMin = 1.0/(min(abs(dir.x), abs(dir.y)) + dirReduce);
	
  dir = min(vec2(FXAA_SPAN_MAX,  FXAA_SPAN_MAX), 
        max(vec2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX), dir * rcpDirMin)) * OGL2InvSize;
		
  vec3 rgbA = (1.0/2.0) * (
              texture2D(OGL2Texture, gl_TexCoord[0].xy + dir * (1.0/3.0 - 0.5)).xyz +
              texture2D(OGL2Texture, gl_TexCoord[0].xy + dir * (2.0/3.0 - 0.5)).xyz);
  vec3 rgbB = rgbA * (1.0/2.0) + (1.0/4.0) * (
              texture2D(OGL2Texture, gl_TexCoord[0].xy + dir * (0.0/3.0 - 0.5)).xyz +
              texture2D(OGL2Texture, gl_TexCoord[0].xy + dir * (3.0/3.0 - 0.5)).xyz);
  float lumaB = dot(rgbB, luma);

  if((lumaB < lumaMin) || (lumaB > lumaMax))
  {
    rgbM = RGBtoYIQ*rgbA;
	rgbM = vec3(pow(rgbM.x,val00.x),rgbM.yz*val00.yz);
    gl_FragColor.xyz=YIQtoRGB*rgbM;
	
  } else {
    rgbM = RGBtoYIQ*rgbB;
	rgbM = vec3(pow(rgbM.x,val00.x),rgbM.yz*val00.yz);
    gl_FragColor.xyz=YIQtoRGB*rgbM;
  }
  gl_FragColor.a = 1.0;
}