Support for arbitrary implementation-specific optimizations. The API allows
particular options to be turned on or off. 'Option' is the number of the
option and 'onoff' is 0 (off) or non-0 (on). The value returned is given
by the PNG_OPTION_ defines below.
HARDWARE: normally hardware capabilities, such as the Intel SSE instructions,
are detected at run time, however sometimes it may be impossible
to do this in user mode, in which case it is necessary to discover
the capabilities in an OS specific way. Such capabilities are
listed here when libpng has support for them and must be turned
ON by the application if present.
SOFTWARE: sometimes software optimizations actually result in performance
decrease on some architectures or systems, or with some sets of
PNG images. 'Software' options allow such optimizations to be
selected at run time.
Section 6: IMPLEMENTATION OPTIONS ******************************************************************************
Support for arbitrary implementation-specific optimizations. The API allows particular options to be turned on or off. 'Option' is the number of the option and 'onoff' is 0 (off) or non-0 (on). The value returned is given by the PNG_OPTION_ defines below.
HARDWARE: normally hardware capabilities, such as the Intel SSE instructions, are detected at run time, however sometimes it may be impossible to do this in user mode, in which case it is necessary to discover the capabilities in an OS specific way. Such capabilities are listed here when libpng has support for them and must be turned ON by the application if present.
SOFTWARE: sometimes software optimizations actually result in performance decrease on some architectures or systems, or with some sets of PNG images. 'Software' options allow such optimizations to be selected at run time.