... in GIMP 2.10.9 from git
In gimppickable-contiguous-region's pixel_difference() function,
which is used, among other things, by the select-by-color and
fuzzy-select tools, when selecting by LCh/HSV hue, treat a pair of
colors as inifinitely far apart if one of them has positive chroma/
saturation, and the other has chroma/saturation that's very close
to 0; conversely, treat a pair of colors as equal if both of them
have chroma/sautation that's close to 0.
As a result, when the seed color is saturated, gray pixels are
never selected, while when the seed color is desaturated, all, and
only, gray pixels are selected.
(cherry picked from commit 9886b69dac)
When clicking on a line art pixel, only this pixel gets colored, which
is fine for actual (original) line art pixels. But on generated ones
(closure pixels, which are internal only), you end up with a single
pixel colored while the whole surrounding area is empty. This feels like
a bug (even though it was not one technically) as you have no way to
guess you are clicking on a closure pixel.
Instead, when this happens, simulate clicks on all neighbour pixels,
hence potentially coloring all surrounding regions, which is most likely
what you wanted.
(cherry picked from commit f310db6c21)
In gimp_pickable_contiguous_region_by_color(), add a small epsilon
to the threshold value, to allow for small errors due to the input
color and pickable pixel-colors being converted to the common
format through different paths.
While we *could* special-case threshold == 0 when the input color
comes from the same pickable, as is the case for the select-by-
color tool, and perform an exact comparison in the original format,
in the more general case the input color can come from an arbitrary
source, such as a plug-in.
(cherry picked from commit a6c79770c3)
