// contour=ps_2_0
// Code from MPC

sampler s0 : register(s0);
float4 p0 : register(c0);

#define width (p0[0])
#define height (p0[1])
#define counter (p0[2])
#define clock (p0[3])

#define PI acos(-1)

float4 main(float2 tex : TEXCOORD0) : COLOR
{
	float dx = 4/width;
	float dy = 4/height;

	float4 c2 = tex2D(s0, tex + float2(0,-dy));
	float4 c4 = tex2D(s0, tex + float2(-dx,0));
	float4 c5 = tex2D(s0, tex + float2(0,0));
	float4 c6 = tex2D(s0, tex + float2(dx,0));
	float4 c8 = tex2D(s0, tex + float2(0,dy));

	float4 c0 = (-c2-c4+c5*4-c6-c8);
	if(length(c0) < 1.0) c0 = float4(0,0,0,0);
	else c0 = float4(1,1,1,0);

	return c0;
}