1  #version 450 core
 2  
 3  layout (std140, binding = 0) uniform ratio_in
 4  {
 5      int ratio;
 6  };
 7  
 8  layout (set = 2, binding = 0) uniform usampler2D src;
 9  layout (set = 3, binding = 0) writeonly uniform uimage2D dst;
10  
11  layout (local_size_x = 32, local_size_y = 32, local_size_z = 1) in;
12  
13  void main()
14  {
15      uvec2 coords = gl_GlobalInvocationID.xy;
16      ivec2 textureSz = textureSize(src, 0);
17  
18      if (int(coords.x) >= textureSz.x || int(coords.y) >= textureSz.y)
19      {
20          return;
21      }
22  
23      uint coordsShifted = coords.x << ratio;
24  
25      uvec2 dstCoords0 = uvec2(coordsShifted, coords.y);
26      uvec2 dstCoords1 = uvec2(coordsShifted + 1, coords.y);
27      uvec2 dstCoords2 = uvec2(coordsShifted + 2, coords.y);
28      uvec2 dstCoords3 = uvec2(coordsShifted + 3, coords.y);
29  
30      uvec4 rgba = texelFetch(src, ivec2(coords), 0);
31  
32      imageStore(dst, ivec2(dstCoords0), rgba.rrrr);
33      imageStore(dst, ivec2(dstCoords1), rgba.gggg);
34      imageStore(dst, ivec2(dstCoords2), rgba.bbbb);
35      imageStore(dst, ivec2(dstCoords3), rgba.aaaa);
36  }