A simple, single-binary program that creates a PNG image of a chess diagram from its FEN record. The diagram style follows the one commonly used in printed books.

For drawing, the program uses a TTF chess font (Merida), so creates high-quality output images independent of size.

FEN notation is extended with dots d and crosses x to mark squares.

The program is created with the goal of rendering FEN in Markdown documents. A Lua filter for Pandoc is included: it replaces code blocks that have fen syntax with the diagrams, embedded in base64 (as data URL). A FEN record should be written on the first line of the code block, options for the fen2png can be written on the second line.

Usage: fen2png [options] <fen> <output-file>
Options:
    --size=<size>  Diagram size (height and width) in pixels (default: 400)
    --bg=<color>   Background color (default: FFFFFF)
    --fg=<color>   Foreground color (default: 0)
    --base64       Base64 output
    --coordinates  Show coordinates on the diagram
    --flip         Flip the diagram
    --auto-flip    Flip the diagram if Black to move

Color must be a hexadecimal number with the four octets from the most to the
least significant represents transparency, red, green, and blue components
respectively. Transparency of 0 means fully opaque.

Positional arguments:
    <fen>          FEN record
    <output-file>  Output file name or "-" for the stdout

The program uses a freeware chess font "Merida" created by Armando Hernandez Marroquin. The program itself dedicated to the public domain.