Original Blizzard encoder is slightly less optimal than our encoder.
While size in RAM in less of a concern for the non-`UNPACKED_MPQS`
build, smaller files are faster to render.
Savings for unpacked and minified MPQs:
* diabdat.mpq: 918,311 bytes.
* hellfire.mpq: 313,882 bytes.
Example player graphics (note that only a few are loaded at any given time for single player):
* diabdat/plrgfx/warrior/: 366,564 bytes.
Example monster graphics savings:
* diabdat/monsters/skelbow: 5,391 bytes.
Based on the implementation from https://github.com/diasurgical/devilutionx-graphics-tools/pull/6
When using `UNPACKED_MPQS`, avoid all the SDL machinery for reading
files.
This is beneficial not only due to reduced indirection but also because
we can test for the file's existence and get the file size without
opening it, which is much faster.
The format is almost identical to CL2, except it uses the frame header
to store frame width and height instead of 5 32-line offsets.
This means we always have access to frame dimensions, so we can use it
as an on-disk format for our graphics as well.
Additionally, we may be able to optimize the rendering even more
in the future now that we have guaranteed knowledge of frame dimensions.
Gleb Mazovetskiy