According to the docs (https://www.php.net/manual/en/function.imagecreatefromwebp.php and https://www.php.net/manual/en/function.imagewebp.php), `false` should be returned on errors (similar to other functions of the `gd` extension), but actually all errors result in a `Fatal Error`. It doesn't look normal when trying to read an empty file or a file in the wrong format causes the program to stop. The problem seems to be related to a mega-patch that replaced `zend_error` with `zend_error_noreturn` almost everywhere. My patch fixes this behavior by switching from `zend_error_noerror` to `gd_error` (i.e. to `E_WARNING` level). All necessary memory cleanup is already in the code (as it was before the "zend_error_noreturn" patch).
Close GH-13774
Propagating lossless conversion from libgd to our bundled gd.
Changing "quantization" to "quality" as in libgd.
Adding test.
IMG_WEBP_LOSSLESS is only defined, if lossless WebP encoding is
supported by the libgd used.
Closes GH-7348.
* --with-webp-dir becomes --with-webp
* --with-jpeg-dir becomes --with-jpeg
* --with-png-dir is removed. libpng is required.
* --with-zlib-dir is removed. zlib is required.
* --with-xpm-dir becomes --with-xpm.
We also enable --with-webp on Travis.
ext/gd/libgd/gd_webp.c has been taken from libgd[1]. Mainly, gd_error(X) has
been subsituted by zend_error(E_ERROR, X) and BGD_DECLARE(X) by X. Further
modifications are obvious from the diff.
All GD tests are passing, what raises hope, but we need more WebP tests,
anyway.
[1] <7ec030c4f1/src/gd_webp.c>
