PixelPal

PixelPal is a command line utility for validating and converting the palette of image (especially pixel art) files.

When using third party pixel art assets, the palettes of different assets may not match. To unify the look of these assets, you might want to convert their color palettes to match.

Usage

PixelPal can be run using a command-line interface:

pixelpal convert [options] <file>...
pixelpal validate [options] <file>...
pixelpal find <file>...

Convert

The convert command converts an image (or multiple images) to a target palette.

Valid options are:

• -h, --help: Show help
• -p, --palette: Name or path (.png) of the palette to use (required)
• -o, --output: Output file(s) (required)
• -c, --contrast: Tolerance of the contrast in percent (default value is 0)
• -l: Tolerance of the L* component in the CIELAB color space (default value is 0)
• -a: Tolerance of the a* component in the CIELAB color space (default value is 0)
• -b: Tolerance of the b* component in the CIELAB color space (default value is 0)
• -s, --stepsize: Step size of each tolerance (default value is 1)

Tolerances represent a spectrum in which the source image can be moved to get a result that better utilizes the target palette, although the higher a tolerance, the more the resulting image may differ from the source image. If for example a contrast tolerance of 10% was chosen, the contrast of the input image may be increased or decreased by up to 10% to make better use of all the colors in the target palette.

The L*a*b* component tolerances control the following:

• L*: A lower L* value darkens the image, a higher value lightens it.
• a*: A lower a* value shifts all colors towards green, a higher value shifts them towards red.
• b*: A lower b* value shifts all colors towards blue, a higher value shifts them towards yellow.

The step size controls the intervals in which the input image is manipulated according to the tolerances. A step size of 5 and a contrast tolerance of 10% means that the following contrasts are used:

• 90%
• 95%
• 100%
• 105%
• 110%

Validate

The validate command checks if an image (or multiple images) uses a palette.

Valid options are:

• -h, --help: Show help
• -p, --palette: Name or path (.png) of the palette to use (required)

Find

The find command finds the palette used by an image (or multiple images).

Valid options are:

• -h, --help: Show help

Contributing

Pull requests are welcome.

Project Structure

The commands of PixelPal are defined in main.go. The options for each command are defined in terminal/terminal.go. The program then gives control to the chosen command in commands/ (e.g. commands/convert.go) to the function with the same name as the command.

Each command function is responsible for its help text, validating required options and of course executing the command itself.

Convert

The convert command executes the following steps:

• It first loads the input files (input images and palette)
• Then it starts converting the input image (or loops through each input image, if multiple are given)
  • The input image is split into tiles (see function split)
  • For each tile, modifiers are calculated (see function calculateModifiers)
  • Each tile gets converted according to its modifier values (see function convertImage)
  • The tiles are joined together again (see function join)
  • The output image gets saved

Validate

The validate command executes the following steps:

• It first loads the input files (input images and palette)
• Then it starts validating the input image (or loops through each input image, if multiple are given)
• For each image, it goes through each pixel and checks if the given palette contains the color of the pixel

Find

The find command executes the following steps:

• It first loads the input images
• Then it goes through each input image and tries to find a matching palette by going through each known palette and checking each pixel of the image against that palette
• If at least one matching palette has been found, the name of the first palette that matches the colors of the input image is printed to the terminal.

Credits

PixelPal is written by Norman Rauschen.

The project uses the following open source packages:

• cli
• color

License

This project is released under the Unlicense.