uniform float4x4  ViewProj;
uniform texture2d image;
uniform float2    outputSize;
uniform float3    colorMatrix0;
uniform float3    colorMatrix1;
uniform float3    colorMatrix2;
uniform float     scale;

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 PSHDRPQ(VertData vert_in) : TARGET
{
  uvec2 outputPos = uvec2(vert_in.uv * outputSize);
  vec4  pixel     = texelFetch(image, ivec2(outputPos), 0);

  /* SMPTE ST.2084 (PQ) EOTF: recover normalised linear light where 1.0
   * corresponds to 10000 cd/m² */
  vec3 e   = pow(max(pixel.rgb, 0.0), vec3(1.0 / 78.84375));
  vec3 num = max(e - 0.8359375, 0.0);
  vec3 den = 18.8515625 - 18.6875 * e;
  vec3 lin = pow(num / den, vec3(1.0 / 0.1593017578125));

  /* convert from the source display primaries to BT.709 in linear light */
  vec3 rgb709 = vec3(
    dot(colorMatrix0, lin),
    dot(colorMatrix1, lin),
    dot(colorMatrix2, lin));

  /* scale to the scRGB reference white convention (1.0 = 80 cd/m²) */
  return float4(rgb709 * scale, pixel.a);
}

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