workaround for resizing problem with animated gifs
relieve the formatter of the responsebility of converting the image color mode
seems like info['loop'] is not always set for gifs
use the color from a previous frame in animations with transparency
change the meaning of --animate and --loop
resize using the ANTIALIAS method from PIL
make the _background property contain rgba data and not single integers
fixed a lot of transparency issus
correct delay between each frame