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How map colors between GIMP and PICASO

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  • How map colors between GIMP and PICASO


    I am trying to get an animation on my uLCD-32PT. I used GIMP to create it. Parts of the animation have to be transparent. Thanks to the ESPsupport, I now know how to do that, The disadvantage of this procedure is that you loose a color. ESPsupport suggested to use an obscure color in gfx_TransparentColour(.....).

    The colors used in PICASO are 16 bit, the colors in GIMP are 24 bit. How can I map the two?

    Example: Suppose I use THISTLE 0xDDFB, then what is the representation in GIMP.

    Or are there other, more suitable, tools to make animations for PICASO environments?



  • #2

    I presume GIMP will be using 8 bit color, 24 bits in total, 8 bits of red, 8 bits of green and 8 bits of blue (an 888 color if yopu like).

    The display uses 565 color, 5 bits of red, 6 bits of green and 5 bits of blue.

    So an 888 color shifted right 323 times (if that makes sense) will give you a 565 color.

    Most transparency schemes 'borrow' a color as the transparent color, AFAIK the only systems you don't lose a color are RGBI and RGBA schemes, i.e. schemes that have extra information beyond RGB.


    • #3

      I think your assumption makes sense since colors on both the uLCD-32PT and my computer screen look very much the same.

      I tried the PICASO color code 0xA55A and translated it into 0xA0A8D0 (GIMP). Unfortunately the transparency did not work.

      To test it, I used the enclosed GIF image. The space outside the circle was filled with the color mentioned.



      Attached files


      • #4

        I'm just going from memory here........
        I did some tests for an earlier project, and I was having problems with color banding when the images were saved as 24 bit and imported into GC.
        In my photo editor, I down converted the image to 16 bits, and still had problems. However, I then allowed dithering during the down conversion, and the results were MUCH better, no banding and looked much closer to the original.
        This was quite a while ago, and with a much older version of GC....
        This does nothing for your transparency issue, but it may help in general?
        Best Regards,


        • #5

          The only further thing I can suggest is that GIMP is probably BGR so the transparent color should be 0xD0A8A0


          • #6

            Thank you for the help and the suggestions.

            I will experiment with them en let you know the outcome.



            • #7

              Some experiments are carried out fast.

              In GIMP:

              FF0000 is red

              00FF00 is green

              0000FF is blue

              Seems to be RGB.




              • #8

                Lets assume you have created the GCI file of your animation and it is the only thing in the GCI (i.e. it begins at offset 0)

                Lets also assume the first pixel of the first frame is the transparent color.

                So now if you look into the GCI with your favourite hex editor and observe the word at offset 8 (0 relative), if it is 0x1234 then the transparent color is 0x1234.

                Hopefully you can work out the location if it doesn't begin at 0, or if the first pixel is not the transparent color.


                • #9

                  Thanks ESPsupport, that helped.

                  I discovered that the colors magically transformed from the intended A55A to 9DA5. When I checked the colors in GIMP, I found that the intended colors transformed from A0A8D0 (24 bit) to 9DA9D0. Some experimenting learned that this occurs during saving the picture as .GIF file.

                  Knowing this, I am now trying to find a more predictable outcome.