GIF - Drawings
One of the main fields of application for GIF are drawings, sketches, etc., which are subject to certain characteristics at the conversion:
Number of Colours
It must be guaranteed, that no colour will be rejected being essential for the picture's information.
Rastered lines, in particular if they have only the strength of one pixel, impair the picture impression considerably. Additionally the compression rate decreases.
Anti-aliasing results in intermediate steps increasing the number of colours. Frequently the number of colours must be manually reduced afterwards, because automatic procedures would reject important contents. Additionally the blurring negatively effect the subjective impression and the compression rate.
If the drawing should be fit into a background, it is advisable to define the background with transparency. Thus disturbing colour deviations will be avoided and no manual changes are necessary for later adaptions.