Shrinko8 - an aggressive cart minifier (+ linter & other tools) - online / lexaloffle

Sometimes your cartridge fits in the token count, but not the characters count / compressed size, so you can’t export it until you reduce the number of characters in the cartridge. - Aggressive Lua code minification and debug code stripping

• r/pico8 - A set of Pico-8 cart tools, with a focus on shrinking code size.

• Tokens: 8192
• Characters: 65’536
• Compressed Code Size: 15’616

Compression limit

Because there is a small, fixed amount of space available to encode the cart in the image, PICO-8 uses compression to reduce the size of the cart’s source code. The compressed code size must be under a certain limit for the save to succeed. As of 0.2.2c, this limit is 15,616 bytes.

PXA File Format

pico8 stores its cartridges in a custom compressed format called PXA. basically, it stores data in chunks. each chunk is a specific type, CHR, REF, or RAW

coming up with new ways to make my code horrific but slightly smaller when compressed:

• changing all my loops (e.g. for j=1,8 do) to use the same index variable (j) and start number, so that the loop header compressed neatly into a larger REF chunk.
• don’t store variables if you can help it. writing x=stat(32) to get the mouse’s xpos and then using it ~6 times was 1 byte longer than just calling stat(32) 6 times. surprising!

see also PXAVizualiser

Compressor

• PX9 / PX8 - PX9 is a lightweight gfx & map compression library, intended to replace PX8. It uses the same ideas and interface as px8, but is smaller (~297~x 214 tokens to decompress), and requires zero configuration.

• New Byte Compressor 2022
• Adventures in data compression (2021) - compare different technics and algorithm in pico-8 context:
  • Vector Distance Transform (VDT)
  • Lempel-Ziv-Welch (LZW) compression
  • Huffman Coding
  • Run length encoding (RLE)
• My Compressor (2018)
• SRAM Smasher! (2018)
• Binary Image Compressor (2016)

see also

• Motivation Crisis: Compression Limit?
• A compressed size limit rant
• Alex Kidd Pico Part 3: Code & Music limitations

Token Optimisation

• PICO-8 Token Optimizations
  • put all your game data into a string. = 1 token

MultiCart

• From one Pico-8 cart to many
  • Picocraft: Pico8 Sprite and maps Tricks - Graphics Workflow with PX9
    • show multicart and upper memory usage

Sprite Optimisation

• rectpack2D / HN - A header-only 2D rectangle packing library written in modern C++.