//========== Copyright (c) Valve Corporation, All rights reserved. ==========//

#define HDRTYPE HDR_TYPE_NONE
#include "common_ps_fxc.h"

// This pixel shader compares the luminance against a constant value and retruns all 1's when greater

sampler TexSampler	: register( s0 );

struct PS_INPUT
{
	float2 uv0						: TEXCOORD0;
};

float3 g_vComparisonMinMaxScale : register( c0 );
#define g_flComparisonMin   g_vComparisonMinMaxScale.x
#define g_flComparisonMax   g_vComparisonMinMaxScale.y

struct PS_OUTPUT
{
    float4 color : COLOR0;
	#ifndef _X360
	    float depth : DEPTH; // Workaround for ATI driver bug
	#endif
};

PS_OUTPUT main( PS_INPUT i )
{
	float3 color = tex2D( TexSampler, i.uv0 );

	// Formula for calculating luminance based on NTSC standard
	float3 tmpv = { 0.2125f, 0.7154f, 0.0721f };
	float flLuminance = dot( color.rgb, tmpv.rgb );

	// Alternate formula for calculating luminance for linear RGB space (Widely used in color hue and saturation computations)
	//float3 tmpv = { 0.3086f, 0.6094f, 0.0820f };
	//float flLuminance = dot( color.rgb, tmpv.rgb );

	// Simple average
	//float flLuminance = ( color.r + color.g + color.b ) * 0.33333f;

	PS_OUTPUT o;
	o.color.rgba = step( g_flComparisonMin, flLuminance ) * step( flLuminance, g_flComparisonMax );
	#ifndef _X360
	{
		o.depth = 0.0f; // Workaround for ATI driver bug
	}
	#endif

	return o;
}