documentation
optimization part one
- identify duplicate frames and rewrite the previous Graphic Control Extension block with an extended frame duration instead
- this safely builds on the fact that going back and changing a frame delay doesn't change the *length* of the GCE block, so nothing after it is overwritten
- also setting up a composite pixel byte array, which while not strictly necessary for this optimization, will be handly later
optimization part 2
- erase bits of the current frame using the transparency color, if they're the same as what would aready be showing
- now we actually make use of the composite array
documentation, usings