ColorPaletteCodable

A color palette reader/editor/writer package for iOS, macOS, macCatalyst, tvOS, watchOS and Linux.

Supports the following :-

Supported palette formats

• Adobe Swatch Exchange (.ase)
• Adobe Photoshop Color Swatch (.aco)
• Adobe Color Table (.act)
• Adobe Color Book (.acb) (read only)
• NSColorList (.clr) (macOS only)
• RGB text files (.rgb)
• RGBA text files (.rgba)
• GIMP palette files (.gpl)
• Paint Shop Pro files (.pal, .psppalette)
• PNG files (.png)
• Microsoft RIFF palette files (.pal) (read only)
• SketchPalette files (.sketchpalette)
• CorelDraw/Adobe Illustrator xml palette (.xml)
• Corel swatches (.txt)
• JSON encoded color files (.jsoncolorpalette) ColorPaletteCodable internal file format
• Hex Color Palette (text file with delimited hexadecimal color strings) (.hex)
• Paint.NET palette files (.txt)
• PNG palette files (.png)
• SVG swatches (.svg) (write only)
• Basic CSV
• Basic XML

Supported gradient formats

• GIMP gradient (.ggr)
• Built-in JSON format gradient (.jsongradient)
• Basic Adobe gradient (.grd) (read only)
• Basic Paint Shop Pro gradient (.pspgradient) (read only)
• SVG Gradient file (.svg) (write only)

Why?

I wanted to be able to read and write Adobe .ase palette files in my Swift app. This then extended to .aco Adobe Photoshop Color Swatch files. Which then expanded to other types :-)

Some features :-

• Named palettes
• Named colors
• Multiple named groups of colors within a single palette
• Colorspace support (RGB, CMYK, Gray) with conversion capabilities
• Encoding/Decoding of all supported palette coder types
• Includes a cross-platorm, human readable, palette coder (json utf8 format)
• Integrated pasteboard support for macOS/iOS
• Simple image generation for an collection of colors
• Gradient support

Online API Documentation

Palette API

Available Coders

Each coder defines .encode and .decode. Not all coders support both encode and decode.

Example usage

Decode a palette file

do {
   let myFileURL = URL(fileURL: ...)
   
   // Try to decode the palette based on its file extension
   let palette = try PAL.Palette.Decode(from: myFileURL)
   
   // do something with 'palette'
}
catch {
   // Do something with 'error'
}

Build a palette and generate an ASE binary representation

// Build a palette
var palette = PAL.Palette()
let c1 = try PAL.Color.rgb(name: "red",   1, 0, 0)
let c2 = try PAL.Color.rgb(name: "green", 0, 1, 0)
let c3 = try PAL.Color.rgb(name: "blue",  0, 0, 1)
palette.colors.append(contentsOf: [c1, c2, c3])

// Generate a simple image from the colors
let image = try PAL.Image.Image(colors: [c1, c2, c3], size: CGSize(width: 100, height: 25))

// Create an ASE coder
let coder = PAL.Coder.ASE()

// Get the .ase format data
let rawData = try coder.encode(palette)
   
// Do something with 'rawData' (like write to a file for example)

Read an ACO file, write an ASE file

let acoFileURL = URL(fileURL: ...)
let coder = PAL.Coder.ACO()
var palette = try coder.decode(from: acoFileURL)
   
// do something with 'palette'
   
// re-encode the palette to an ASE format
let encoder = PAL.Coder.ASE()
let rawData = try encoder.encode(palette) 

Palette format encoding/decoding limitations

(A ColorType represents the type of color (global/spot/normal))

Gradients

The library defines PAL.Gradients which defines a collection of colors with positions that can be used when using a gradient. Certain gradient types (eg. .grd) support multiple gradients within the same file.

Gradient API

Available Coders

• .ggr support doesn't respect segment blending functions other than linear (always imported as linear)
• .ggr support doesn't allow for segment coloring functions other than rgb (throws an error)
• .grd support is very basic at this point. There's no formal document for it, and I built this using very vague documents 1, 2
  • doesn't (currently) support encode
  • Only user colors are supported in the gradients (ie. book colors aren't supported)
  • Noise gradients aren't supported
  • only rgb, cmyk, hsb, gray colors are supported
• .pspgradient appears to be equal to the grd v3 format. (Read only)

For some nice gradient files

• cptcity has all of them :-)
• lospec

cptcity also has a nice converter for gradients to ggr

Examples

Create a gradient

let gradient = PAL.Gradient(
   colorPositions: [
      (0.0, try PAL.Color(rgbHexString: "#FFFFFF")),
      (0.5, try PAL.Color(rgbHexString: "#444444")),
      (1.0, try PAL.Color(rgbHexString: "#000000"))
   ]
)

// Create a gradients container
let gradients = PAL.Gradients(gradients: [gradient])

// Create the appropriate coder
let coder = PAL.Gradients.Coder.GGR()

// Encode the gradient using the GIMP gradient encoder
let data = try coder.encode(gradients)

// Decode a gradient from data
let decoded = try PAL.Gradients.Decode(
   from: data,
   fileExtension: PAL.Gradients.Coder.GGR.fileExtension
)

Load a gradient

// Load a gradient from a file, inferring the type from the file's extension
let gradient1 = try PAL.Gradients.Decode(from: fileURL)

// Load a specific gradient format from a file
let coder = PAL.Gradients.Coder.GRD()
let gradient2 = try coder.decode(from: i)

Palette Viewer

Palette Viewer allows you to view the contents of all supported palette and gradient files

You can drag colors out of the preview window into applications that support dropping of NSColor instances.

You can also save the palette to a new format (eg. saving a gimp .gpl format to an Adobe .aco format)

QuickLook support

This package also includes a Quicklook Plugin for palette and gradient files.

In the Quicklook subfolder you'll find an xcodeproj which you can use to build the application Palette Viewer which contains the QuickLook plugin.

For the plugin to register, you need to run the application. After the first run the QuickLook plugin will be registered.

Linux support

• Linux only supports very naive color conversions between RGB-CMYK-Gray.

To build/test linux support using a mac

See: Testing Swift packages on Linux using Docker

1. Install Docker Desktop for Mac on your mac
2. Make sure that docker is running (or else the next command will fail with a weird or no error message)
3. Run the following command in the directory you want to mirror in your linux

docker run --rm --privileged --interactive --tty --volume "$(pwd):/src" --workdir "/src" swift:latest

Now, from within the docker container, run

swift build
swift test

Note that the /src directory in the Linux container is a direct mirror of the current directory on the host OS, not a copy. If you delete a file in /src in the Linux container, that file will be gone on the host OS, too.

Format specs

The .ase file format is not formally defined, however there are a number of deconstructions available on the web. I used the breakdown of the format defined here.

The .aco file format is defined here.

The .act file format is defined here.

The .acb format discussed and deined here

The CorelDraw/Adobe Illustrator .xml file format is (somewhat) defined here

GRD references

• http://www.selapa.net/swatches/gradients/fileformats.php
• https://github.com/Balakov/GrdToAfpalette/blob/master/palette-js/load_grd.js
• https://github.com/abought/grd_to_cmap/blob/master/grd_reader.py
• https://github.com/tonton-pixel/json-photoshop-scripting/tree/master/Documentation/Photoshop-Gradients-File-Format#descriptor

License

MIT License

Copyright (c) 2024 Darren Ford

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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SOFTWARE.