[vox-tech] GIMP and 8-bit GIFs

[nbs]

On Mon, Jul 01, 2002 at 11:36:03AM -0700, Alexandra Thorn wrote:
> 
> I need to create some images for some old software that can only handle
> 8-bit graphics (GIF87).  I've been messing with the GIMP, trying to create
> things in the right format, and am getting a little frustrated.  Can
> someone tell me how to do this?

WHen you're all done creating the image and are ready to save as GIF,
you can do one of two things:

  1. Save the image and let The Gimp convert it for you:

     Simply right-click the canvas, select "File", "Save As...", and then
     enter the name for the file, ending it with ".gif"
     (With the "Determine File Type:" pulldown set to "By Extension,"
     it'll just know.)

     When it goes to save, you should get a pop-up window labelled
     "Export File," which lets you have Gimp either convert the image to
     8-bit color, or 8-bit greyscale.  Click "Export" and it will save.

     Your image, as it lives in Gimp, is unchanged.  You'll want to
     load up the saved GIF file (in Gimp, Netscape, XV, whatever...) to
     make sure it looks ok.

or:

  2. Convert the image to 8-bit depth BEFORE saving:

     Right-click the canvas, select "Image", "Mode", "Indexed..."
     Choose your setting sin the "Indexed Color Conversion" window that
     pops up.

     Here, you can choose the number of colors (256 or less will save ok
     as GIF) and let The Gimp pick the best colors.
     ("Generate Optimal Palette.")

     Or... you can use a custom palette of colors, and have the best
     matches picked from it.  (e.g., the "Web" palette of 216 so-called
     "web safe" color)  ("Use Custom Palette")  [*]

     Finally, you can also just save in two colors: black, and white.
     ("Use Black/White (1-Bit) Palette")

     You can also choose how the resulting image is "dithered."
     Solid-colored images (e.g. cartoonish) should probably have
     "No Color Dithering," while something that was photographic or
     rendered, or has nice dropshadows or other 'colorful' details
     should have one of the other dithering options.
     I usually use "Floyd-Steinberg Color Dithering (Reduced Color Bleeding)"


     [*] To create a palette to use in the "Indexed Color Conversion"
         dialog, you can:

       1. Edit the color palette using The Gimp's palette editor:

          Right-click the canvas, select "Dialogs" and "Palette."
          Click "Edit" in the "Color Palette" window.
          (You can first pick some different existing palette from
          within the "Select" tab at the top of this window, BTW.)

          You can now edit, delete, import, and merge palettes.
          I won't go into too many details, but let's say you want to
          make a new palette.

          Click "New" (one of the "Palette Ops" at the right of the
          "Color Palette Edit" window).  Give your palette a name.
          Now you can create and edit colors in the palette.
          On the left area of the window, right-click.

          In the pop-up menu, select "New."  It will add a
          black (0x00, 0x00, 0x00) pixel to the palette (at the far left).
          Right click it (you can't really see it unfortunately, but it's
          there, at the very, very far left) and select "Edit" from the
          pop-up menu.

          Now you'll see a "Color Selection" dialog, which you should be
          used to from using The Gimp.  Set the color, hit OK.

          Lather, rinse, repeat.  :)

      or:

        2. Create some image (a 16x16 picture, for example) and draw colored
           pixels into it.  (Use the "Pencil" tool in the toolbox, and
           use the tiny 1x1 brush.)

           *Ack* - I need to run to lunch, and forget exactly what you need
           to do now, but it has something to do with saving or exporting
           some file into your "~/.gimp-1.2/palettes/" directory.

           Sorry :)

      or:

        3. Edit / make new palettes by hand in a text edtiro.
           The files inside your "~/.gimp-1.2/palettes/" directory are
           simply plain text files that look something like:

           GIMP Palette
           # My stupid palette
           123 123 123 grey
           255 255 255
           0 0 0 black
           0 0 255 Beautiful Blue
           0 255 0


Anyway - gotta run to lunch!  Enjoy! :)

-bill!