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These changes improve readability without negatively affecting correctness or performance. 1) The code to do horizontal and vertical scaling were mostly identical. This change merges them. 2) The case where the original and result sizes were identical were handled inefficiently (and probably incorrectly) by copying the source to the destination with memcpy. This change makes a simple copy if both dimensions are the same (i.e. no resizing is requested) and skips resizing in the unchanged dimension if only one dimension is different. 3) Other cleanups: removed dead code, improved variable names, added assertions to document expections, etc.
For documentation, browse index.html. Quick install guide: If the sources have been fetched from git, run bootstrap.sh [options]. From a released source, use: 1. Type './configure' 2. Type 'make install' Generic configuration instructions are in the file INSTALL. The following 3rd-party libraries will be used by gd if found by configure. While gd will compile and install even without these, we suggest that at least zlib and libpng are installed, and recommend that freetype and jpeg are installed as well: 1. zlib, available from http://www.gzip.org/zlib/ Data compression library 2. libpng, available from http://www.libpng.org/pub/png/ Portable Network Graphics library; requires zlib 3. FreeType 2.x, available from http://www.freetype.org/ Free, high-quality, and portable font engine 4. JPEG library, available from http://www.ijg.org/ Portable JPEG compression/decompression library 5. XPM, available from http://koala.ilog.fr/lehors/xpm.html X Pixmap library If any of these libraries are installed, but not detected by configure, you can use the following command line options: --with-png=DIR Without the DIR argument, configure will check for png header files and libraries in a default location. To switch off png support, use --without-png, or --with-png=no. If the DIR argument is specified, configure tries to find the png header files in DIR/include, and the libraries in DIR/lib. To accommodate OpenBSD ports, DIR/include/libpng is also checked if necessary. --with-freetype=DIR Dto. for freetype 2.x library. The search path for include files is DIR/include/freetype2. --with-jpeg=DIR Dto. for jpeg library. --with-xpm=DIR Dto. for xpm library. --with-tiff=DIR Dto. for TIFF library.