#include "../shaderenv.h"


struct frag
{
	 // normalized screen position
	float2 texCoord: TEXCOORD0; 

	float2 lt: TEXCOORD1; // left top
	float2 rb: TEXCOORD2; // right bottom
	float2 rt: TEXCOORD3; // right top
	float2 lb: TEXCOORD4; // left bottom
};


struct pixel
{
	float4 col: COLOR0;
};


float4 DownSample(frag IN,
				  uniform sampler2D colors,
				  float2 downSampleOffs[16]) : COLOR
{    
    float4 average = .0f;

    for(int i = 0; i < 16; ++ i)
    {
        average += tex2D(colors, IN.texCoord + downSampleOffs[i]);
    }
        
    average *= 1.0f / 16.0f;

    return average;
}
    

float4 GreyScaleDownSample(frag IN,
						   uniform sampler2D colors
						   ): COLOR
{

	// Compute the average of the 4 necessary samples
	float average = .0f;
	float maximum = .0f;

	// the rgb weights
	const float3 w = float3(0.299f, 0.587f, 0.114f);
	//float3 w = float3(0.2125f, 0.7154f, 0.0721f);

	float4 cols[4];

	cols[0] = tex2D(colors, IN.lt);
	cols[1] = tex2D(colors, IN.lb);
	cols[2] = tex2D(colors, IN.rt);
	cols[3] = tex2D(colors, IN.rb);

	for (int i = 0; i < 4; ++ i)
	{
		const float intensity = dot(cols[i].rgb, w);

		maximum = max(maximum, intensity);
		average += log(1e-5f + intensity);
	}

	average = exp(average * 0.25f);

	float4 hcols = cols[0] + cols[1] + cols[2] + cols[3];

	return hcols * 0.25f;
	//return float4(average, maximum, 0.0f, cols[0].w);

	// Output the luminance to the render target
	//return float4(average, maximum, 0.0f, 1.0f);
}
    

pixel ToneMap(frag IN,
			  uniform sampler2D colors,
			  uniform float imageKey, 
			  uniform float whiteLum, 
			  uniform float middleGrey)
{
	pixel OUT;
	float4 color = tex2D(colors, IN.texCoord);

	const float pixLum = 0.2125f * color.x + 0.7154f * color.y + 0.0721f * color.z;
	
	// obtain new image key from highest mipmap level
	float logLumScaled = tex2Dlod(colors, float4(.5f, .5f, 0, 99)).w;
	float logLum = logLumScaled * LOGLUM_RANGE + MINLOGLUM;

	float newImageKey = exp(logLum);

	// adjust to middle gray
	const float lum = middleGrey * pixLum / newImageKey;
	 
	// map to range and calc burnout
	const float scaleLum = lum * (1.0f + lum / whiteLum * whiteLum) / (1.0f + lum);

	OUT.col = color * scaleLum / pixLum;
	OUT.col.w = color.w;

	return OUT;
}