When downscaling raster brushes, we currently resample the original
brush with no fitlering (other than bilinear interpolation), which
results in very noticable aliasing when using heavily downscaled
big brushes.
This commit constructs a box-filtered mipmap hierarchy for the
original brush on-demand, and the closest mipmap is used as the
resampling source for downscaled brushes, significantly improving
the output quality.
... which converts a (scale, aspect_ratio) pair to a (scale_x,
scale_y) pair.
Change gimp_brush_transform_matrix() to take (scale_x, scale_y)
parameters, instead of (scale, aspect_ratio), and change the rest
of the code accordingly.
The parallel_distribute() family of functions has been migrated to
GEGL. Remove the gimp_parallel_distribute() functions from
gimp-parallel, and replace all uses of these functions with the
corresponding gegl_parallel_distrubte() functions.
The next commit is going to parallelize gimpbrush-transform using
the gimp_parallel_distribute_foo() functions. To spare us a lot of
boilerplate code, we're going to use C++ lambdas as callback
arguments to these functions.
This commit does the initial conversion of gimpbrush-transform.c to
C++, renaming it to gimpbrush-transform.cc. We do this in a
separate commit, so that the changes are small enough for git to
register this as a renamed file, rather than a new file, so that we
don't lose the file's history.
Ell