The color components are supposed to be in range 0..255, so we must not
cast them to `signed char`, what can be the default for `char`.
Port of <https://github.com/libgd/libgd/commit/77c8d359>.
The recently introduced test_image_equals_file() doesn't properly work for
palette images, because in this case only the palette indexes are compared,
what can lead to false positives and negatives as shown in the added test.
To fix that we convert palette images to truecolor, what is supposed to be
faster than calling imagecolorsforindex() for each pixel.
We furthermore rely on PHP's refcounting to free unused images; after all,
this is not C.
Firstly, there is no fundamental difference between running the tests on
freetype before and after 2.4.10, so we re-join the respective test cases.
Secondly, there are some minor differences in the results depending on
architecture, freetype versions and config options, so we cater to that
by allowing small deviations from the expectations.
Apparently, different FreeType versions render the string differently, so
we have to cater to these slight differences. Unfortunately, the testing
framework doesn't yet offer a clean API for this, so we work around the
limitations by parsing and checking the output of test_image_equals_file().
The behavior of imagecropauto($im, IMG_CROP_DEFAULT) is rather different
for the bundled and an external libgd, see
<https://github.com/libgd/libgd/issues/298>.
Therefore we split the test for now.
This test case fails with external libgd, because libgd < 2.2.4 converts
palette images to truecolor (<https://github.com/libgd/libgd/issues/297>).
However, even if there happens no truecolor conversion, it is not guaranteed
that the palette indexes of the original and the cropped image are identical
(this is, for instance, not the case with current libgd master where the bug
has been fixed). Therefore we check for the expected RGBA value instead of
the palette index.
The bundled GD test suites makes heavy use of md5() to verify the result
of drawing operations. This leads to fragile tests (even a slight change
in a PNG header would cause failure, and of course there is the
possibility of collisions), and even worse, eventual test failures are
rather unrevealing.
Therefore we replace all md5() verification with a simplistic
test_image_equals_file(), which is basically a simplified port of libgd's
gdTestImageCompareToFile(), adapted to the needs of PHPTs.
In the long run better tests helpers should be introduced (see also
<http://news.php.net/php.internals/94081>), but for now this solution
is preferable over the former.
(cherry picked from commit 24f9e96792)
gdImageTrueColorToPalette() is sometimes wasteful by putting multiple white
color entries into the palette. This is caused by an obvious typo, where
to avoid a division by zero when `total` is zero, `count` is checked instead
of `total`.
We fix this issue to improve the quality of the color quantization.
Cf. <https://github.com/libgd/libgd/commit/24b4550f>
Christoph M. Becker