46 lines
1.4 KiB
Plaintext
46 lines
1.4 KiB
Plaintext
let DITHER_BASE = 16;
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let BIT_WIDTH = 16;
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let DITHER_SIZE = 0x10000;
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fn bit_reverse(_x: u32) -> u32 {
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var x = _x;
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var hi = u32(1) << (u32(BIT_WIDTH)-u32(1));
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var lo = u32(1);
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for (var i = u32(0); i < u32(BIT_WIDTH)/u32(2); i = i + u32(1)) {
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let bit_hi = x & hi;
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let bit_lo = x & lo;
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x = x & ~hi & ~lo;
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if (bit_hi > u32(0)) { x = x | lo; }
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if (bit_lo > u32(0)) { x = x | hi; }
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hi = hi >> u32(1);
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lo = lo >> u32(1);
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}
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return x;
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}
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fn bit_interleave(x: u32, y: u32) -> u32 {
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var mask = u32(1) << (u32(BIT_WIDTH)-u32(1));
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var acc = u32(0);
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for (var i = u32(0); i < u32(BIT_WIDTH); i = i + u32(1)) {
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acc = acc | ((x & mask) << u32(2)*i + u32(1));
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acc = acc | ((y & mask) << u32(2)*i);
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mask = mask >> u32(1);
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}
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return acc;
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}
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fn bayer(coord: vec2<u32>) -> f32 {
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let magic = bit_reverse(bit_interleave(coord.x ^ coord.y, coord.x));
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return (f32(magic+u32(1)) / (f32(DITHER_SIZE)*f32(DITHER_SIZE))) - 0.5;
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}
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fn bayer_bias(_pixel: vec2<u32>) -> vec4<f32> {
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let pixel = _pixel % u32(DITHER_SIZE);
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return vec4<f32>(
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bayer(pixel),
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bayer(vec2<u32>(u32(DITHER_SIZE) - pixel.x - u32(1), pixel.y)),
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bayer(vec2<u32>(pixel.x, u32(DITHER_SIZE) - pixel.y - u32(1))),
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bayer(vec2<u32>(u32(DITHER_SIZE) - pixel.x - u32(1), u32(DITHER_SIZE) - pixel.y - u32(1)))
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);
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}
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