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png: Correct endianness for big-endian machines

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libpng wants to receive samples in either RGB or RGBA order, whether
each sample is big-endian or not. This resolves test failures in
testsuite/gdk/memorytexture.c (and a lot of reftests) on s390x, and
probably the PowerPC family too.

Modifying the test to show the color in use and write out the PNG bytes
to a file, and running the memorytexture test on s390x, produces a PNG
that loads with the correct color values in GIMP (on an x86_64 machine),
which seems like evidence that this is the correct change and not just
compensating errors.

Resolves: https://gitlab.gnome.org/GNOME/gtk/-/issues/4616
Signed-off-by: Simon McVittie <smcv@debian.org>
This commit is contained in:
Simon McVittie 2022-01-08 16:39:36 +00:00
parent bed67edd2e
commit 979c124e57
1 changed files with 0 additions and 16 deletions
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16
gdk/loaders/gdkpng.c
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@ -222,11 +222,7 @@ gdk_load_png (GBytes *bytes,
case PNG_COLOR_TYPE_RGB_ALPHA:
if (depth == 8)
{
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
format = GDK_MEMORY_R8G8B8A8;
#elif G_BYTE_ORDER == G_BIG_ENDIAN
format = GDK_MEMORY_A8B8G8R8;
#endif
}
else
{
@ -236,11 +232,7 @@ gdk_load_png (GBytes *bytes,
case PNG_COLOR_TYPE_RGB:
if (depth == 8)
{
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
format = GDK_MEMORY_R8G8B8;
#elif G_BYTE_ORDER == G_BIG_ENDIAN
format = GDK_MEMORY_B8G8R8;
#endif
}
else if (depth == 16)
{
@ -325,22 +317,14 @@ gdk_save_png (GdkTexture *texture)
case GDK_MEMORY_A8R8G8B8:
case GDK_MEMORY_R8G8B8A8:
case GDK_MEMORY_A8B8G8R8:
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
format = GDK_MEMORY_R8G8B8A8;
#elif G_BYTE_ORDER == G_BIG_ENDIAN
format = GDK_MEMORY_A8B8G8R8;
#endif
png_format = PNG_COLOR_TYPE_RGB_ALPHA;
depth = 8;
break;
case GDK_MEMORY_R8G8B8:
case GDK_MEMORY_B8G8R8:
#if G_BYTE_ORDER == G_LITTLE_ENDIAN
format = GDK_MEMORY_R8G8B8;
#elif G_BYTE_ORDER == G_BIG_ENDIAN
format = GDK_MEMORY_B8G8R8;
#endif
png_format = PNG_COLOR_TYPE_RGB;
depth = 8;
break;