CHRxPNG

View and convert NES CHR files to PNG images and vice versa

Use your favorite sprite & tile sheet graphics tool such as GrafX2 (which is mine for this task) and create the CHR files necessary for NES development. Or create nice and colorful PNGs from CHR files.

How to use

Just drag and drop your CHR or PNG file — either into the window or onto the app icon.

PNG images are expected to be 128 pixels wide and either 128 or 256 pixel high. If more than 4 colors are used in the image, CHRxPNG will tell you. But the PNG does not have to be 2-bit. Anything will do as long as only 4 colors are used.

CHRs can be either 4.096 or 8.192 bytes (actually, they can be any size, but these are the two sizes most suitable for me).

Functions

Apart from opening a file CHRxPNG is totally controlled by key commands.

• Open a file by dragging and dropping either a CHR or a PNG file into the window or onto the app icon.
• [B] to switch banks (only available if more than one bank is needed to display the CHR or PNG)
• [G] to turn tile grid on and off
• [P] to switch palettes; you can cycle through nine 4-color palettes (only available for CHR files)
• [S] to save as PNG or CHR, depending on the current type of file, to the folder specified in the dialog box (either ~/Library/Application Support/LOVE/CHRxPNG on macOS or %appdata%\LOVE\CHRxPNG on a Windows machine)
• [Esc] to exit CHRxPNG

Built-in Palettes

CHR tile sets can be viewed with different 4-color palettes. When loading a PNG the corresponding image colors are used and cannot be changed. However, the palette chosen for a CHR is saved when exporting to PNG.

The palettes for coloring the CHR files are the following:

• 2-Bit Grayscale
• Kirokaze Gameboy
• 2Bit Demichrome
• Nintendo Super Gameboy
• Nintendo Gameboy BGB
• Pokémon SGB
• CGA Palette 1 High
• Kid Icarus SGB
• Super Mario Land 2 SGB

But, why…?

I needed something sweet and simple to view and convert CHRs. And something that is able to work with 8-Bit PNGs, too. So I coded my own tool. It is made with LOVE and it does the job quite nicely. It also features several beautiful 4-color palettes from Lospec.

--

2022 by Marc Oliver Orth | @marc2o

https://marc2o.github.io