#include <metal_stdlib>
using namespace metal;

struct VertexOut {
    float4 position [[position]];
    float2 texCoord;
};

vertex VertexOut vertex_main(uint vertexID [[vertex_id]]) {
    float2 pos[] = {
        {-1.0, -1.0},
        { 1.0, -1.0},
        {-1.0,  1.0},
        { 1.0,  1.0},
    };

    float2 uv[] = {
        {0.0, 1.0},
        {1.0, 1.0},
        {0.0, 0.0},
        {1.0, 0.0},
    };

    VertexOut out;
    out.position = float4(pos[vertexID], 0.0, 1.0);
    out.texCoord = uv[vertexID];
    return out;
}

fragment float4 fragment_main(VertexOut in [[stage_in]],
                              texture2d<float> tex [[texture(0)]]) {
    constexpr sampler s(filter::linear);
    return pow(tex.sample(s, in.texCoord), 0.45f);
}