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This is packchr, a tool that finds unique tiles in NES character (CHR)
files.

packchr is intended to be used to convert logos, title screens, cut
scene images etc. into a representation suitable for display on the
NES.

See INSTALL for installation instructions.

See doc/index.html for documentation, or do "man packchr" after
installation.

packchr does not deal with palette data. You have to ensure that you
set up the NES palette properly yourself.

The whole process goes something like this:

1. Prepare your artwork as raw CHR in whatever way you like; e.g. by
using a tile editor, or an image converter, or a hex editor (extra
points!).

2. Run packchr with your raw CHR as input. This produces a new CHR
with dupe tiles removed, and a raw nametable.

3. Run packnam with the nametable produced by packchr as
input. Remember to specify the correct --width parameter, and
--vram-address (unless you want the image to show up in the top-left
corner on the NES).

4. Prepare a CHR bank containing the CHR produced by packchr. This is
the bank that you have to load into NES video memory when you want to
display the image; i.e. it must be part of your NES ROM. packchr's
--character-size option can be useful; use it to produce a file that's
exactly 1K/2K/4K, then this step is a no-op. If your bank is 1K or 2K,
make sure that you transpose the nametable tile indexes if necessary,
by specifying a --nametable-base when invoking packchr; for example,
if your bank is 1K and will reside at address 0x0C00 in NES video
memory, you should use --nametable-base=0xC0; otherwise the tile
indexes and the location of the CHR won't match, and the NES will
display junk.

5. Include the packed nametable produced by packnam in your NES
ROM. Write 6502 code that loads it (see the packnam README for
details). Compile the ROM and hope it works.