PixelWorld

Internal ZX Spectrum font conversion, ripping and manipulation tool made public!

This is a tool I have been using for a number of years to convert my own fonts into a variety of formats available from https://damieng.com/fonts/zx-origins/

It also contains bulk-ripping dump and hunt commands for obtaining ZX Spectrum RAW 768 byte/.ch8 files from memory dumps and snapshots.

The code is in need of clean-up in various places, please bear with me.

Commands

Ripping

• dump to RAM-dump snapshot files (currently supports .z80 and .sna and recurses through .zip archives)
• hunt to look through RAM dumps for possible bitmap fonts (currently supports only ZX Spectrum fonts)
• screenshot to create a screenshot from a RAM-dump or snapshot files (in PNG, SCR or animated GIF format)

Conversions

The following commands work against the ZX Spectrum RAW 768 byte/.ch8 files:

• preview to create a .png preview file

Any of the following assembly generating commands can use the --base hex|decimal flags. The z80 one can also use --base binary.

• z80asm to create Zilog Z80 assembler source with defb hex
• x86asm to create Intel 8086 assembler source with db hex
• 6502asm to create MOS 6502 assembler source with .byte hex
• 68000asm to create Motorola 68000 assembler source with DB.B hex

And the C-generating command:

• chead to generate C-compatible header files

You can also generate directly-usable files (all binary except the CPC)

• zxtofzx to create a fixed-width .fzx
• zxtofzx --proportional to create a proportional .fzx by auto left aligning and measuring widths
• zxtocbm to create .c64 and .bin binary ROM versions for the Commodore 64
• zxtoa8 to create a .fnt binary version for the Atari 8-bit series
• zxtocpc to create a .bas BASIC file for use with the Amstrad CPC range

Any command can be further detailed using the --help option which will detail the additional flags and options available.

Hunt strategies

Finding bitmap fonts in a raw memory dump isn't trivial as there's no specific header however there are a few different strategies available in the code that can be combined and tweaked, they are:

EnvironmentGuidedFinder

This relies on programmers using the ROM routines to print text to the screen and is surprisingly successful. It basically looks for a font at whatever RAM location is specified at memory locations 23606 & 23607. It can only find one font however so games like Millionaire that use several get missed.

KnownCharPatternFinder

This looks for fonts based on well-known glyphs that designers rarely changed such as the copyright symbol and by using their known position in the font works out where the font is located.

CandidatesInWindowFinder

This provides an array of potential glyphs without any knowledge of what they actually are. It requires you pass a certain number of glyphs and looks to find a minimum amount of them in a sequence in RAM.

This works in conjunction with SpectrumDisplay.GetCandidates to divide the current screen memory into as many unique 8x8 character blocks as it can. The principle here is that the font is probably used on-screen and is aligned to the usual (32x24) text grid.

GeneralHeuristicFinder

This finder looks for fonts by expecting certain pixel densities in relative to each other. For example ! should have less pixels than m. c should have less pixels than o etc.

Setup

The project should compile with VS 2019 or later.

Some template files are necessary for the conversions and should have their location specified by the --templatePath parameter.

• atari8.fnt - A dump of the Atari system font that includes all the symbols characters etc.
• c64-both.c64 - A dump of the Commodore 64 upper+lower case
• c64-upper.c64 - A dump of the Commodore 64 upper case + symbols

Example usage

Various different usages of this command can be fount in my ZX Origins font-publishing script - every reference there to pw.exe is this.