Re: [Gimp-user] Help with color of several shades

[Akkana Peck <akkana shallowsky com>]

SArtino writes:
> I suggested painting the wood edges to a bright
> green because we make no blend that contains green, sowe can use a single photo
> of one brick wall, and change the color of the green mortar joint to whatever.  
> 1 photo of each wall blend, edit 20 different mortar colors. Sounds like a
> simple idea right?
> * http://www.gimpusers.com/system/attachments/242/original/IMG_20160413_133407.jpg

This was a week ago so it may be moot by now, but since I didn't see
any other replies: one thing you can try is different settings of
Select by: in the Tool options for Select by Color. You could try
either Hue (since the mortar is greener than everything else),
Saturation (since the brick color isn't saturated but the mortar is)
or Green. Don't forget that Select by Color lets you drag to adjust
how much is selected: up/left to select less, down/right to select
more. It looks to me like with that image, Green isn't working at
all but Hue and Saturation both work a lot better than the default
of Composite.

You'll still need to clean up your selection after making it,
either by copying it to a layer mask or by editing it in the
quickmask. Use Levels to threshold it (Threshold handles only black
and white so you get hard edges; adjusting the middle slider in
Levels usually gives a better result, with gradual edges). You
might also want to use Dilate, Erode and Blur, and maybe paint
over a few areas that didn't work out quite right.

Good luck!

        ...Akkana