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>
These functions may be used in tight loops to do image manipulation in
userland. Using FAST_ZPP is supposed to bring considerable performance
improvements in this case; we've been able to measure up to 25%.
PNG allows identical images to be stored differently what makes nearly all
tests checking the MD5 hash of the PNG representation fail with external
libgd. For now, we use the GD format instead, which doesn't allow for such
differences.
Of course, this md5() checking should be replaced by a image diffing feature
in the long run.
GD:
- PrintWindow() is available as of Windows XP, it requires linking to User32.lib, which config.w32 for ext/gd already.
CLI:
- The borrowed functions from PostgreSQL to set the titles of the console window uses SetConsoleTitle() and GetConsoleTitle(), both are available as of Windows 2000 from Kernel32.lib which we already are linking against.
Standard:
- The disk space utility functions uses GetDiskFreeSpaceExA() which is available as of Windows XP, again links to Kernel32.lib.
- The symlink() PHP function uses CreateSymbolicLinkA() which is available from Windows Vista, again from Kernel32.lib.
- php_get_windows_name() in info.c uses GetNativeSystemInfo() which is available as of Windows XP and GetProductInfo() which is available as of Windows Vista, both are again from Kernel32.lib.
Notes:
- ext/interbase & ext/pdo_firebird uses GetProcAddress(), I'm not entirely sure how to handle this one.
- ext/sqlite3, this is apart of the bundled libsqlite3, I don't really wanna play around with our bundled libs and make it a bigger issue for those who maintain and upgrade them.
- ext/readline, the call to GetProcAddress() here does not do any system calls, so it is left as is.
- win32/ioutil.c uses GetProcAddress(), but the function it attempts to load (PathCchCanonicalizeEx()) is only available from Windows 8 and greater (Pathcch.lib linkage).
- win32/time.c uses GetSystemTimePreciseAsFileTime() which is available from Windows 8 and greater to get the current system date and time which the highest possible precision and falls back to GetSystemTimeAsFileTime() (available as of Windows 2000), again Kernel32.lib, the GetSystemTimePreciseAsFileTime() is left in a GetProcAddress().
Calling imagesetstyle() with an empty $styles array caused gdImageSetStyle()
to be called with `noOfPixels==0`, what could have lead to OOB reads.
Actually, this issue will be fixed in libgd, but to avoid issues when older
libgd is in use, we simply disallow passing an empty $styles array to
imagesetstyle(), what wouldn't serve a useful purpose anyway.
Christoph M. Becker