chromaticAberration.metal

kernel void chromaticAberration(
                                texture2d<float, access::write> outTex [[texture(0)]],
                                texture2d<float, access::read> inTex [[texture(1)]],
                                uint2 gid [[thread_position_in_grid]]) {
    float filterLevel = 3.5;
    float4 c = float4(0.0, 0.0, 0.0, 1.0);
    //収差に使用するレイヤーの色味
    float3 weight[4] = {
        float3(0.0f, 0.0f, 0.5f),
        float3(0.0f, 0.5f, 0.5f),
        float3(0.5f, 0.5f, 0.0f),
        float3(0.5f, 0.0f, 0.0f)
    }
    //正規化
    float nx = ((float)(gid.x)/(outTex.get_width()/2.0) - 1.0);
    float ny = ((float)(gid.y)/(outTex.get_height()/2.0) - 1.0);

    for (int i=0; i<4; i++) {
        unsigned int xo = (int)((float)(gid.x) - nx * filterLevel * i);
        unsigned int yo = (int)((float)(gid.y) - ny * filterLevel * i);
        float3 split = weight[i];
        float3 src = inTex.read(uint2(xo, yo)).rgb;
        c.rgb += src.rgb * split;
    }
    outTex.write(c.rgba, gid);
}