layout(set=0, binding=0) writeonly buffer destBuffer{
    FLOAT4 data[];
} uOutput;

layout(set=0, binding=1) readonly buffer sourceBuffer0{
    FLOAT4 data[];
} uInput;

layout(set=0, binding=2) uniform constBuffer {
    ivec4 inputSize;
    ivec4 outputSize;
    ivec2 pad;
    ivec2 kernelSize;
    ivec2 stride;
} uConstant;

layout (local_size_x = 8, local_size_y = 8, local_size_z = 1) in;

void main()
{
    ivec3 pos = ivec3(gl_GlobalInvocationID);
    ivec3 outputSize = uConstant.outputSize.xyz;
    ivec2 spos = pos.xy*uConstant.stride-uConstant.pad;

    if (all(lessThan(pos, outputSize)))
    {
        ivec2 inputSizeXY = uConstant.inputSize.xy;
        FLOAT4 color = FLOAT4(-100000.0);
        ivec2 sfxy = max(ivec2(0), -spos);
        ivec2 efxy = min(uConstant.kernelSize, inputSizeXY-spos);

        for (int fy=sfxy.y; fy<efxy.y; ++fy)
        {
            for (int fx=sfxy.x; fx<efxy.x; ++fx)
            {
                ivec2 spos_ = spos + ivec2(fx, fy);
                FLOAT4 inputColor = uInput.data[0
                + pos.z * uConstant.inputSize.y * uConstant.inputSize.x
                + spos_.y * uConstant.inputSize.x
                + spos_.x
                ];
                color = max(inputColor, color);
            }
        }
        uOutput.data[0
            + pos.z * uConstant.outputSize.x * uConstant.outputSize.y
            + pos.y * uConstant.outputSize.x
            + pos.x
            ] = color;
    }
}