Many tools for creating background tiles and sprites for the Sega Master System (SMS) are only available on the Windows operating system, making it challenging for macOS and Linux users.
This small Go language library was created to aid developers converting raster images (e.g. PNG) to the SMS tile, palette, and tilemap (name table) data.
The source image is converted into 8x8 pixel tiles, duplicate tiles are removed (using both vertical and horizontal flipping comparison). SMS colour palette data is generated from the image, and a tilemap is generated.
Note: if the colours in the source image do not match exactly those on the SMS, a nearest match conversion will be attempted. This can have an undesirable effect, so it's recommend to follow the image generation guide below.
If you have Go installed on your system you can use the following command to
install smstilemap:
go install github.com/mrcook/smstilemap/cmd/smstilemap@latest
Usage of smstilemap:
-in string
Input PNG filename
-out string
Output directory for generated files (default: input filename directory)
-fmt string
Output format: asm, tiles (default "asm")
-v Display version number
To convert an image to Sega Master System assembly code:
smstilemap -in=/path/to/image.png
This will generate a Z80 assembly source code file (.asm) comprising of the SMS tile,
tilemap, and palette data, in the same directory as the image: /path/to/image.asm.
To specify a different output directory, use the -out flag. For example:
smstilemap -in=/path/to/image.png -out=/output/dir
which will write the data as: /output/dir/image.asm.
Along with ASM code, it's also possible to output a PNG image containing all
the unique tiles from the source image (tile data), by using the -fmt=tiles
CLI option.
smstilemap -in=/path/to/image.png -fmt=tiles
The 1983 ZX Spectrum JETPAC game loading screen (without colour clash!):
As a set of unique tiles:
Any graphics or sprite editor that can control the colour palette and export to PNG can be used.
Master System specs:
- 256x192 pixels screen size (viewport)
- 64 predefined colours
- 32 palette colours: 16 for background tiles and 16 for sprites or background tiles
- tile size: 8x8 pixels
- maximum of 448 unique tiles
When creating the source image, the above dimensions, colours, and palette size should be used.
The Master System screen viewport would require 768 unique tiles to fill it. As the SMS can only hold a maximum of 448 tiles, images need to be crafted for tile re-use. Careful alignment along 8 pixel boundaries and utilising flipped tiles (vertical and horizontal) can help to achieve this maximum tile usage.
A small utility called smscolours is provide that will generate PNG files for
all the colours generated by the Sega Master System and Game Gear consoles.
These files can then be used as palette files for your favourite sprite editor
(Krita, LibreSprite, etc.).
Install smscolours by running the following command:
go install github.com/mrcook/smstilemap/cmd/smscolours@latest
Once installed run the program while specifying an output directory:
smscolours /path/to/output/dir/
Example output: sms-colours.png
Copyright (c) 2021-2023 Michael R. Cook. All rights reserved.
This work is licensed under the terms of the MIT license. For a copy, see https://opensource.org/licenses/MIT.
Various snippets of information from the SMS Power website have been reproduced in the source code comments.