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stb_image: Trivial optimizations for filter path when img_n==out_n.

This commit is contained in:
Fabian Giesen 2014-12-13 17:22:57 -08:00
parent 00965512d7
commit 61428d4526
1 changed files with 5 additions and 3 deletions
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8
stb_image.h
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@ -2526,12 +2526,13 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
prior += out_n;
// this is a little gross, so that we don't switch per-pixel or per-component
if (img_n == out_n) {
int nk = (x - 1)*img_n;
#define CASE(f) \
case f: \
for (i=x-1; i >= 1; --i, raw+=img_n,cur+=img_n,prior+=img_n) \
for (k=0; k < img_n; ++k)
for (k=0; k < nk; ++k)
switch (filter) {
CASE(STBI__F_none) cur[k] = raw[k]; break;
// "none" filter turns into a memcpy here; make that explicit.
case STBI__F_none: memcpy(cur, raw, nk); break;
CASE(STBI__F_sub) cur[k] = STBI__BYTECAST(raw[k] + cur[k-img_n]); break;
CASE(STBI__F_up) cur[k] = STBI__BYTECAST(raw[k] + prior[k]); break;
CASE(STBI__F_avg) cur[k] = STBI__BYTECAST(raw[k] + ((prior[k] + cur[k-img_n])>>1)); break;
@ -2540,6 +2541,7 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
CASE(STBI__F_paeth_first) cur[k] = STBI__BYTECAST(raw[k] + stbi__paeth(cur[k-img_n],0,0)); break;
}
#undef CASE
raw += nk;
} else {
STBI_ASSERT(img_n+1 == out_n);
#define CASE(f) \