LookingGlass/obs/effect/rgb24.effect

uniform float4x4  ViewProj;
uniform texture2d image;
uniform float2    outputSize;
uniform int       swap;

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

VertData VSDefault(VertData vert_in)
{
  VertData vert_out;
  vert_out.pos = mul(float4(vert_in.pos.xyz, 1.0), ViewProj);
  vert_out.uv  = vert_in.uv;
  return vert_out;
}

float4 PSColorFilter(VertData vert_in) : TARGET
{
  uvec2 outputPos = uvec2(vert_in.uv * outputSize);

  uint fst     = outputPos.x * 3u / 4u;
  vec4 color_0 = texelFetch(image, ivec2(fst, outputPos.y), 0);
  
  uint snd     = (outputPos.x * 3u + 1u) / 4u;
  vec4 color_1 = texelFetch(image, ivec2(snd, outputPos.y), 0);

  uint trd     = (outputPos.x * 3u + 2u) / 4u;
  vec4 color_2 = texelFetch(image, ivec2(trd, outputPos.y), 0);
  
  vec4 result = vec4(
    color_0.barg[outputPos.x % 4u],
    color_1.gbar[outputPos.x % 4u],
    color_2.rgba[outputPos.x % 4u],
    1.0
  );

  if (swap == 1)
    return result.rgba;
  else
    return result.bgra;
}

technique Draw
{
  pass
  {
    vertex_shader = VSDefault(vert_in);
    pixel_shader  = PSColorFilter(vert_in);
  }
}