Apply patch from upstream 9c4f5f11802c 'Adjust shadow to equally
darken and lighten'. The waved flags were noticeably darker than
the source image, for example the blue of the Russian flag was too
dark.
Previously our copy of waveflag took just an input and output filename.
Upstream takes a prefix and one or more input filenames, and concatenates
the prefix to the input filename as the output.
The makefile is changed to pass a prefix and the input filename, instead
of the input filename and the output filename as it formerly did.
Unfortunately for us, our inputs have a directory prefix since they're
not in the current directory, and we don't want this prefix in the output
file path. So we tweak our copy of waveflag.c to call basename on the
input file path before we append it to the prefix.
We also make the tool a little less noisy by putting more printfs
under the debug flag.
When waveflag.c was forked from behdad's repo one of the changes that
was made effectively removed the ability to generate different sizes
of flags, despite leaving the SIZE value in the source. Recently we
needed to generate waved flags at a different power-of-two size, and
found it no longer functioned as the original. These changes restore
that while leaving the other changes in this forked version (mostly
formatting changes) intact.
