tei/MapLibreParticleLab
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

manually premultiply the image if libpng can't do it

Browse Source
This commit is contained in:
Konstantin Käfer
2015-08-04 17:45:26 +02:00
parent 3b4a0b228c
commit 56a4268cca
1 changed files with 15 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
platform/default/png_reader.cpp
View File

@@ -160,8 +160,6 @@ void PngReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, char *
#ifdef PNG_ALPHA_PREMULTIPLIED
png_set_alpha_mode(png_ptr, PNG_ALPHA_PREMULTIPLIED, PNG_GAMMA_LINEAR);
#else
// TODO: Manually premultiply the image data.
#endif
if (x0 == 0 && y0 == 0 && w >= width_ && h >= height_)
@@ -180,6 +178,20 @@ void PngReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, char *
for (unsigned row = 0; row < height_; ++row)
rows[row] = (png_bytep)image + row * width_ * 4 ;
png_read_image(png_ptr, rows.get());
fprintf(stderr, "manual premultiplication\n");
#ifndef PNG_ALPHA_PREMULTIPLIED
// Manually premultiply the image if libpng didn't do it for us.
for (unsigned row = 0; row < height_; ++row) {
for (unsigned x = 0; x < width_; x++) {
png_byte* ptr = &(rows[row][x * 4]);
const float a = ptr[3] / 255.0f;
ptr[0] *= a;
ptr[1] *= a;
ptr[2] *= a;
}
}
#endif
}
else
{
@@ -193,6 +205,7 @@ void PngReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, char *
png_read_row(png_ptr,row.get(),0);
if (i >= y0 && i < (y0 + h))
{
// TODO: premultiply this
std::copy(&row[x0 * 4], &row[x0 * 4] + w * 4, image + i * width_* 4);
}
}