GIF - Optimized Colour Tables

GIF offers the opportunity to use individual colour tables, so the question arises how this may be utilised. Most applications for picture processing provide functions to generate those tables. Afterwards they may be optimized manually or automatically.

Such routines try to determine which combination of colours is approximately the best. The most simple option is the selection of those colours appearing most frequently. However rarely used colours may disappear thereby, which are of great importance for the picture's contents like labels, legends or marks.

In such a case it is the best to reduce gradually the number of colours and to see, when unacceptable changes appear. If this border is exceeded, one needs to reactivate the last file. Additionally one has the possibility to adapt the colour allocation manually e.g. after unwanted changes.

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