This project contains the source code to the inkpot cli, a tool that can be used to convert JPEG, PNG and GIF images to 4-bit, 16-color grayscale images. The image format is designed to be simple to decode.
# inkpot help A command-line-tool that can be used to prepare images by resizing them, rotating them and converting them to 16-color grayscale so they can be comfortably displayed on e-ink displays powered by the epdiy driver. Usage: inkpot-cli [command] Available Commands: completion Generate the autocompletion script for the specified shell convert Convert a single file to a 4-bit, 16-color grayscale image help Help about any command serve Run a webserver to convert images via HTTP Flags: -h, --help help for inkpot-cli Use "inkpot-cli [command] --help" for more information about a command.
The package is written in go and you can use all the standard go tooling to run and build the binary. The individual commands are defined in the
cmd/ folder, the encoding / decoding bits are in
If you are using the nix package manager, there is a description of the build and dev environment in
flake.lock. It is recommended to use https://direnv.net/ with flakes support.
Image Format (in progress)
An image blob starts with a header containing ascii-encoded key-value pairs. It holds meta-information (such as an image's
h), where case-insensitive keys are separated from values using a space and a colon character (
: ). A value ends with a newline character (
\n). The end of the header data is marked by two consecutive newline characters (
The actual image data is following the header as a sequence of nibbles, or groups of four bits. Each nibble determines the grayscale value of a single pixel, where the first
w nibbles designate the grayscale values of the first row of pixels (0 is black and 16 is white from left to right, the group of nibbles from
w + 1 to
2w the second row of pixels from left to right and so on.