GNOME Bugzilla – Bug 313666
RGB->Indexed mode switch loses text's antialiasing
Last modified: 2008-01-15 12:58:49 UTC
Distribution/Version: Win2K 1) Create a new blank image 2) Type some text with antialiasing on 3) Zoom in to see the off-color pixels from the antialiasing 4) Do Image>Mode>Indexed with any settings 5) See the antialiased pixels disappear This does not happen when doing 'Save a copy as .gif' with automatic flatten and convert (but than the default convert is web-safe, not adaptive) Possible workaround: Manually flatten image before converting, but that looses all the layers.
Not really, the GIMP display just tricks you into believing that there would only be 1bit transparency. This design decision was made in the days when GIF was the only format to save indexed images in. The GIF format doesn't support full alpha transparency. The image window shows you what the GIF will look like.
*** This bug has been marked as a duplicate of 86627 ***
So, to confirm that I understand it. The correct way to do this IS flatten and than convert to indexed, because if we convert first, the text layer does its indexing against transparency/white and not against other visible layers? Is this something that is worth documenting, because it is not obvious why Merge,Indexed is not the same as Indexed,Merge with all the other factors equal.
If you plan to save to GIF then you should definitely flatten before you convert to indexed. This is not obvious to you?
It was obvious to me that I need to both flatten and index at some point, but it was not obvious that I had to do it in the specific order (flatten before index). This is especially so because when I am not happy with default export flatten and index because the index is web-safe. I am likely to go back and try to do manual indexing (as suggesting), but leaving the flatten step to the automatic export. This is also what I would expect a beginner to do by just following GIMPs user-friendly suggestion in the export dialog.