Quote:Second problem : how can I use a background (picture or photo) in the animation?
This first: Make your animation as a RGB sequence. There are plugins / scripts that will add a background image to each layer. Ofnuts has one that works with RGB mode. http://sourceforge.net/projects/gimp-too...s/scripts/ ofn-interleave-layers.zip (dated 2020-04-25)
You are probably better off using Ofnuts plugin in RGB mode but there is an alternative (works with indexed as well) is Saul Goodes script http://chiselapp.com/user/saulgoode/repo...combine-bg
Quote:if I animate a scene in gimp, then the moving object is perfect blending out. When I export the animation to a gif file, then the blending out disappeard.
Why the first quest last ? Transparency in an indexed image is binary, either on or off. To get a fade out (using layers of deceasing opacity). First convert the image to indexed Image -> Mode -> Indexed using the dithering option.
Then you can add a background using Saul Goodes script and finaly export as an animated gif.