Re: [Gimp-user] Converting from indexed to RGB modes; brush color off

[Gary Aitken <gimp dreamchaser org>]

On 12/20/19 8:37 PM, Maxomega wrote:
> So I was editing a sprite sheet for a video game character, and after
> working with it for a bit, I noticed the color I was using was off
> from the brush color. Later, I noticed the layers were behaving
> strange, and that it probably had something to do with being in
> indexed mode.
>
> I changed the image to RGB mode, but my brush color is still off, and
> layering multiple brush colors combines the colors for some reason.
> My brushes are at 100 hardness and 100% opacity, so I don't know what
> the issue could be. I'm just trying to paint over all the color in
> the image to be 00FF00, or the greenest green.
>
> First attached is a screenshot of the base image, unpainted. Also
> included is the brush color, which already doesn't match the outside.
> Note that the top layer is the active one.
>
> Second attached is what happens when I try to draw over the image
> with a plain green brush. The black rectangle is the boundary of the
> middle layer, but I'm not sure why it's black at all.
>
> Third attached is what happens when I try to do same thing (painting
> with the green brush), but with the second layer active.
>
> I'm just really confused. I don't know much about GIMP, but I've been
> using it for well over 5 years and I've never come across something
> like this.
>
> Attachments: *
> https://www.gimpusers.com/system/attachments/1316/original/Capture.PNG
* https://www.gimpusers.com/system/attachments/1317/original/Capture2.PNG
> *
> https://www.gimpusers.com/system/attachments/1318/original/Capture3.PNG
I don't know much about this, but doing some fiddling around I've
discovered the following:

  If the original indexed colormap does not contain the color you desire,
  painting will paint black:

    1.  create an 8 bit integer color image, transparent background
        change the image color mode to indexed
        change the paint foreground color to full green
        painting in the image will paint black

    2.  create an 8 bit integer color image, transparent background
        change the paint foreground color to full green
        paint in the image => paints green
        change the image color mode to indexed
        paint in the image => paints green

I don't know if this is intentional or not; I would have thought that if
the original color index map is not full, using a new color would add it
to the map, but apparently not.

By default, when you choose convert to indexed mode, the colormap chosen
is "Generate optimum palette" with a maximum number of colors of 255.
The "Remove unused and duplicate colors from colormap" option is checked.
You cannot uncheck it.  To uncheck it, switch to custom palette mode,
uncheck it, and then switch back to generate an optimum palette.
Unfortunately, doing this has no affect; the generated palette still
contains only the existing colors, and no holes for additional colors.

I would suggest you create a new colormap with only the colors you wish
to use in your images:
  Windows/Dockable Dialogues/Palettes

I would suggest reading the following sections of the 2.10 user manual:
  2.4 Colormap Dialog
 12.1 Palettes/Colormap
  3.5 Palettes Dialog (esp. the Note)

Gary