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stb_image_write: optimize other PNG loops besides previous merge

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This commit is contained in:
Sean Barrett 2019-02-07 08:13:56 -08:00
parent d27796b585
commit ddccc72c5b
1 changed files with 10 additions and 15 deletions
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25
stb_image_write.h
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@ -1049,16 +1049,14 @@ static void stbiw__encode_png_line(unsigned char *pixels, int stride_bytes, int
unsigned char *z = pixels + stride_bytes * (stbi__flip_vertically_on_write ? height-1-y : y); unsigned char *z = pixels + stride_bytes * (stbi__flip_vertically_on_write ? height-1-y : y);
int signed_stride = stbi__flip_vertically_on_write ? -stride_bytes : stride_bytes; int signed_stride = stbi__flip_vertically_on_write ? -stride_bytes : stride_bytes;
// sorry for not optimizing the other paths if (type==0) {
if(type==0)
{
memcpy(line_buffer, z, width*n); memcpy(line_buffer, z, width*n);
return; return;
} }
// first loop isn't optimized since it's just one pixel
for (i = 0; i < n; ++i) { for (i = 0; i < n; ++i) {
switch (type) { switch (type) {
case 0: line_buffer[i] = z[i]; break;
case 1: line_buffer[i] = z[i]; break; case 1: line_buffer[i] = z[i]; break;
case 2: line_buffer[i] = z[i] - z[i-signed_stride]; break; case 2: line_buffer[i] = z[i] - z[i-signed_stride]; break;
case 3: line_buffer[i] = z[i] - (z[i-signed_stride]>>1); break; case 3: line_buffer[i] = z[i] - (z[i-signed_stride]>>1); break;
@ -1067,16 +1065,13 @@ static void stbiw__encode_png_line(unsigned char *pixels, int stride_bytes, int
case 6: line_buffer[i] = z[i]; break; case 6: line_buffer[i] = z[i]; break;
} }
} }
for (i=n; i < width*n; ++i) { switch (type) {
switch (type) { case 1: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - z[i-n]; break;
case 0: line_buffer[i] = z[i]; break; case 2: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - z[i-signed_stride]; break;
case 1: line_buffer[i] = z[i] - z[i-n]; break; case 3: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - ((z[i-n] + z[i-signed_stride])>>1); break;
case 2: line_buffer[i] = z[i] - z[i-signed_stride]; break; case 4: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - stbiw__paeth(z[i-n], z[i-signed_stride], z[i-signed_stride-n]); break;
case 3: line_buffer[i] = z[i] - ((z[i-n] + z[i-signed_stride])>>1); break; case 5: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - (z[i-n]>>1); break;
case 4: line_buffer[i] = z[i] - stbiw__paeth(z[i-n], z[i-signed_stride], z[i-signed_stride-n]); break; case 6: for (i=n; i < width*n; ++i) line_buffer[i] = z[i] - stbiw__paeth(z[i-n], 0,0); break;
case 5: line_buffer[i] = z[i] - (z[i-n]>>1); break;
case 6: line_buffer[i] = z[i] - stbiw__paeth(z[i-n], 0,0); break;
}
} }
} }