FreeImage_SwapColors not working on palletized image

[KanedaFr]

Hi,

I think I found something strange with FreeImage_SwapColors.
If I have a pallete with these values [blue, red, green, yellow, orange]
and use FreeImage_SwapColors(dib, &pal[0], &pal[3], TRUE), the result is
[yellow, red, green, yellow, orange] and not
[yellow, red, green, blue, orange]

Looking at FreeImage_ApplyColorMapping source code made me think the swap is similar to
srccolor = dstcolor
dstcolor = srccolor
related to misuse of pointers which, obviously, doesn't work.

So I had to made the swap myself with

    palette = FreeImage_GetPalette(dib);
    //not working
    //FreeImage_SwapColors(dib, &palette[0], &palette[transparency], TRUE);
    palTmp.rgbBlue = palette[transparency].rgbBlue;
    palTmp.rgbGreen = palette[transparency].rgbGreen;
    palTmp.rgbRed = palette[transparency].rgbRed;

    palette[transparency].rgbBlue = palette[0].rgbBlue;
    palette[transparency].rgbGreen = palette[0].rgbGreen;
    palette[transparency].rgbRed = palette[0].rgbRed;

    palette[0].rgbBlue = palTmp.rgbBlue;
    palette[0].rgbGreen = palTmp.rgbGreen;
    palette[0].rgbRed = palTmp.rgbRed;

hope this will help to fix this issue

OF course, if I missed something, just tell me and forgive me ;)

KanedaFr

[Hervé Drolon]

Hi,

FreeImage_SwapColors expect 2 RGBQUADs pointers on entry but also expect that these pointers have no link with the palette array (also true for FreeImage_ApplyColorMapping).
That's why your test case doesn't work.

We could add a check for pointers and handle your use case, or explicitly document the fact that input RGBQUADs parameters should have no link with the palette array.

Hervé