uniform sampler2D u_TextureMap;
uniform sampler2D u_LevelsMap;

uniform vec4      u_Color;

uniform vec2      u_AutoExposureMinMax;
uniform vec3      u_ToneMinAvgMaxLinear;

varying vec2      var_TexCoords;

const vec3  LUMINANCE_VECTOR =   vec3(0.2125, 0.7154, 0.0721); //vec3(0.299, 0.587, 0.114);

vec3 FilmicTonemap(vec3 x)
{
	const float SS  = 0.22; // Shoulder Strength
	const float LS  = 0.30; // Linear Strength
	const float LA  = 0.10; // Linear Angle
	const float TS  = 0.20; // Toe Strength
	const float TAN = 0.01; // Toe Angle Numerator
	const float TAD = 0.30; // Toe Angle Denominator
	
	vec3 SSxx = SS * x * x;
	vec3 LSx = LS * x;
	vec3 LALSx = LSx * LA;
	
	return ((SSxx + LALSx + TS * TAN) / (SSxx + LSx + TS * TAD)) - TAN / TAD;

	//return ((x*(SS*x+LA*LS)+TS*TAN)/(x*(SS*x+LS)+TS*TAD)) - TAN/TAD;

}

void main()
{
	vec4 color = texture2D(u_TextureMap, var_TexCoords) * u_Color;
	vec3 minAvgMax = texture2D(u_LevelsMap, var_TexCoords).rgb;
	vec3 logMinAvgMaxLum = clamp(minAvgMax * 20.0 - 10.0, -u_AutoExposureMinMax.y, -u_AutoExposureMinMax.x);
		
	float avgLum = exp2(logMinAvgMaxLum.y);
	//float maxLum = exp2(logMinAvgMaxLum.z);

	color.rgb *= u_ToneMinAvgMaxLinear.y / avgLum;
	color.rgb = max(vec3(0.0), color.rgb - vec3(u_ToneMinAvgMaxLinear.x));

	vec3 fWhite = 1.0 / FilmicTonemap(vec3(u_ToneMinAvgMaxLinear.z - u_ToneMinAvgMaxLinear.x));
	color.rgb = FilmicTonemap(color.rgb) * fWhite;
	
	gl_FragColor = clamp(color, 0.0, 1.0);
}