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Simplify mingle_2bpp_planes

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Fixes #891
This commit is contained in:
Rangi 2022-04-17 15:27:31 -04:00
parent dc121712fe
commit 8c77d6b6d3
1 changed files with 2 additions and 2 deletions
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4
tools/bpp2png.c
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@ -70,8 +70,8 @@ void mingle_2bpp_planes(uint8_t *bpp_data, long size) {
for (long i = 0; i < size; i += 2) {
// Interleave aka "mingle" bits
// <https://graphics.stanford.edu/~seander/bithacks.html#Interleave64bitOps>
#define EXPAND_PLANE(b) (((b) * 0x0101010101010101ULL & 0x8040201008040201ULL) * 0x0102040810204081ULL)
uint16_t r = ((EXPAND_PLANE(bpp_data[i]) >> 49) & 0x5555) | ((EXPAND_PLANE(bpp_data[i + 1]) >> 48) & 0xAAAA);
#define EXPAND_PLANE(b) (((((b) * 0x0101010101010101ULL & 0x8040201008040201ULL) * 0x0102040810204081ULL) >> 48) & 0xAAAA)
uint16_t r = (EXPAND_PLANE(bpp_data[i]) >> 1) | EXPAND_PLANE(bpp_data[i + 1]);
bpp_data[i] = r >> 8;
bpp_data[i + 1] = r & 0xff;
}