Sets precompression filter used when saving images with lossless compression.

published property PreFilter: LongInt read FPreFilter write FPreFilter;

Allowed values are: 0 (none), 1 (sub), 2 (up), 3 (average), 4 (paeth), 5 (use 0 for indexed/gray images and 4 for RGB/ARGB images), 6 (adaptive filtering - use best filter for each scanline - very slow). Note that filters 3 and 4 are much slower than filters 1 and 2. Default value is 5.