uniform float4x4 ViewProj;
uniform texture2d image;
uniform int size;

sampler_state pixelSampler {
	Filter		= Point;
	AddressU	= Clamp;
	AddressV	= Clamp;
};

struct VertData {
	float4 pos : POSITION;
	float2 uv  : TEXCOORD0;
};

VertData vertex_program(VertData vd)
{
	vd.pos = mul(float4(vd.pos.xyz, 1.0), ViewProj);
	return vd;
}


// -------------------------------------------------------------------------------- //
// Helpers
// -------------------------------------------------------------------------------- //
uint get_selector(VertData vd, int width) {
	return uint(vd.uv.x * size * width) % width;
}

// -------------------------------------------------------------------------------- //
// Pack/Unpack RG/GR
// -------------------------------------------------------------------------------- //
float4 _PackRG(VertData vd) : TARGET {
	if (get_selector(vd, 2) == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	}
}
technique PackRG { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackRG(vd); } }

float4 _PackGR(VertData vd) : TARGET {
	if (get_selector(vd, 2) == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	}
}
technique PackGR { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackGR(vd); } }

// -------------------------------------------------------------------------------- //
// Pack/Unpack RGB/BGR
// -------------------------------------------------------------------------------- //
float4 _PackRGB(VertData vd) : TARGET {
	uint select = get_selector(vd, 3);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	}
}
technique PackRGB { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackRGB(vd); } }

float4 _PackBGR(VertData vd) : TARGET {
	uint select = get_selector(vd, 3);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	}
	return float4(0., 0., 0., 0.);
}
technique PackBGR { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackBGR(vd); } }

// -------------------------------------------------------------------------------- //
// Pack/Unpack RGBA/ABGR
// -------------------------------------------------------------------------------- //
float4 _PackRGBA(VertData vd) : TARGET {
	uint select = get_selector(vd, 4);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else if (select == 2) {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).a, 0., 0., 1.);
	}
}
technique PackRGBA { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackRGBA(vd); } }

float4 _PackABGR(VertData vd) : TARGET {
	uint select = get_selector(vd, 4);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).a, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	}
}
technique PackABGR { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackABGR(vd); } }

// -------------------------------------------------------------------------------- //
// Pack/Unpack ARGB/BGRA
// -------------------------------------------------------------------------------- //
float4 _PackARGB(VertData vd) : TARGET {
	uint select = get_selector(vd, 4);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).a, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	} else if (select == 2) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	}
}
technique PackARGB { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackARGB(vd); } }

float4 _PackBGRA(VertData vd) : TARGET {
	uint select = get_selector(vd, 4);
	if (select == 0) {
		return float4(image.Sample(pixelSampler, vd.uv).b, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).g, 0., 0., 1.);
	} else if (select == 1) {
		return float4(image.Sample(pixelSampler, vd.uv).r, 0., 0., 1.);
	} else {
		return float4(image.Sample(pixelSampler, vd.uv).a, 0., 0., 1.);
	}
}
technique PackBGRA { pass { vertex_shader = vertex_program(vd); pixel_shader = _PackBGRA(vd); } }