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Add support for displaying correct colors with PNG files that contain embedded ICC color profiles

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Kovid Goyal
2020-08-12 07:48:47 +05:30
parent 6ca1b7c240
commit 5eefd41059
9 changed files with 69 additions and 9 deletions
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45
kitty/png-reader.c
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@@ -7,8 +7,10 @@
#include "png-reader.h"
#include "state.h"
#include <lcms2.h>
static cmsHPROFILE srgb_profile = NULL;
struct fake_file { const uint8_t *buf; size_t sz, cur; };
static void
@@ -64,13 +66,30 @@ inflate_png_inner(png_read_data *d, const uint8_t *buf, size_t bufsz) {
bit_depth = png_get_bit_depth(png, info);
double image_gamma;
int intent;
cmsHPROFILE input_profile = NULL;
cmsHTRANSFORM colorspace_transform = NULL;
if (png_get_sRGB(png, info, &intent)) {
// do nothing since we output sRGB
} else if (png_get_gAMA(png, info, &image_gamma)) {
if (image_gamma != 0 && fabs(image_gamma - 1.0/2.2) > 0.0001) png_set_gamma(png, 2.2, image_gamma);
} else {
// do nothing since we don't know what gamma the source image is in
// TODO: handle images with color profiles
// Look for an embedded color profile
png_charp name;
int compression_type;
png_bytep profdata;
png_uint_32 proflen;
if (png_get_iCCP(png, info, &name, &compression_type, &profdata, &proflen) & PNG_INFO_iCCP) {
input_profile = cmsOpenProfileFromMem(profdata, proflen);
if (input_profile) {
if (!srgb_profile) {
srgb_profile = cmsCreate_sRGBProfile();
if (!srgb_profile) ABRT(ENOMEM, "Out of memory allocating sRGB colorspace profile");
}
colorspace_transform = cmsCreateTransform(
input_profile, TYPE_RGBA_8, srgb_profile, TYPE_RGBA_8, INTENT_PERCEPTUAL, 0);
}
}
}
// Ensure we get RGBA data out of libpng
@@ -93,9 +112,17 @@ inflate_png_inner(png_read_data *d, const uint8_t *buf, size_t bufsz) {
if (d->decompressed == NULL) ABRT(ENOMEM, "Out of memory allocating decompression buffer for PNG");
d->row_pointers = malloc(d->height * sizeof(png_bytep));
if (d->row_pointers == NULL) ABRT(ENOMEM, "Out of memory allocating row_pointers buffer for PNG");
for (int i = 0; i < d->height; i++) d->row_pointers[i] = d->decompressed + i * rowbytes;
for (int i = 0; i < d->height; i++) d->row_pointers[i] = d->decompressed + i * rowbytes * sizeof(png_byte);
png_read_image(png, d->row_pointers);
if (colorspace_transform) {
for (int i = 0; i < d->height; i++) {
cmsDoTransform(colorspace_transform, d->row_pointers[i], d->row_pointers[i], d->width);
}
cmsDeleteTransform(colorspace_transform);
}
if (input_profile) cmsCloseProfile(input_profile);
d->ok = true;
err:
if (png) png_destroy_read_struct(&png, info ? &info : NULL, NULL);
@@ -130,8 +157,20 @@ static PyMethodDef module_methods[] = {
{NULL, NULL, 0, NULL} /* Sentinel */
};
static void
unload(void) {
if (srgb_profile) cmsCloseProfile(srgb_profile);
srgb_profile = NULL;
}
bool
init_png_reader(PyObject *module) {
if (PyModule_AddFunctions(module, module_methods) != 0) return false;
if (Py_AtExit(unload) != 0) {
PyErr_SetString(PyExc_RuntimeError, "Failed to register the PNG library at exit handler");
return false;
}
return true;
}