We have to make sure to avoid alpha-blending issues by explicitly
switching to `gdEffectReplace` and to restore the old value afterwards.
We also document the algorithm used by `gdImageGrayScale()` and note
its limitations regarding palette images.
This makes the code better readable in the sources, and we get syntax
highlighting in the generated HTML wherever we want it (i.e. not necessarily
always as with `-hl all`).
It is the responsibility of the build infrastructure or user to set or
not set NDEBUG. For the time being this is a workaround in the case
where NDEBUG is set by the build infrastructure or user which prevents
the compiler from generating macro redefiniton warnings/errors. A longer
term fix will require changes to booststrap (aka configure) as well as
cmake (aka CMakeLists.txt).
gdImageCopyGaussianBlurred() returns a blurred copy of its argument.
Blurring is done in two passes to take advantage of the Gaussian
function's separability for. This makes the algorithm much faster
than single-pass implementations, especially for larger radii.
This change also adds documentation for the new function and the
existing blur (gdImageGaussianBlur()).
Mike Frysinger
willson-chen
Christoph M. Becker
David Chappelle
Pierre Joye
Chris Reuter
Ondřej Surý
tabe