Package for Color Processing in Julia 📂Julia

Package for Color Processing in Julia

Introduction¹

Introducing the capabilities of Colors.jl, a package for color processing in Julia. When using the visualization package Plots.jl, there’s no need to load Colors.jl separately. It provides the following functionalities:

Color parsing and conversion
Color maps
Color scales

Parsing and Conversion

Assuming str is a string representing color information, you can parse the string into a color code of a specific color space using @colorant_str or parse(Colorant, str). Note that colorant means a dye or pigment.

julia> using Colors

julia> colorant"red"
RGB{N0f8}(1.0,0.0,0.0)

julia> colorant"rgb(255, 0, 0)"
RGB{N0f8}(1.0,0.0,0.0)

julia> parse(Colorant, "rgba(0, 255, 0, 0.5)")
RGBA{N0f8}(0.0,1.0,0.0,0.502)

julia> parse(Colorant, "#FF0000")
RGB{N0f8}(1.0,0.0,0.0)

julia> parse(Colorant, "hsl(120, 100%, 25%)")
HSL{Float32}(120.0f0,1.0f0,0.25f0)

The convert() function can be used to convert to a color code of a different color space.

julia> convert(RGB, HSL(270, 0.5, 0.5))
RGB{Float64}(0.5,0.25,0.75)

Color Interpolation

Using the range() function, colors can be interpolated. This operation is quite logical and intuitive. For example, consider the RGB codes. Red is represented by $(255, 0, 0)$ or $(1, 0, 0)$ , which is essentially a 3D vector. Therefore, there’s no reason not to use the color code as an argument for the range() function which interpolates between two vectors.

julia> v1 = [1.0, 0.0, 0.0];

julia> v2 = [0.0, 0.5, 0.0];

julia> collect(range(v1, v2, length = 15))
15-element Vector{Vector{Float64}}:
 [1.0, 0.0, 0.0]
 [0.9285714285714286, 0.03571428571428571, 0.0]
 [0.8571428571428572, 0.07142857142857142, 0.0]
 [0.7857142857142857, 0.10714285714285714, 0.0]
 [0.7142857142857143, 0.14285714285714285, 0.0]
 [0.6428571428571428, 0.17857142857142858, 0.0]
 [0.5714285714285714, 0.21428571428571427, 0.0]
 [0.5, 0.25, 0.0]
 [0.4285714285714286, 0.2857142857142857, 0.0]
 [0.3571428571428571, 0.32142857142857145, 0.0]
 [0.2857142857142857, 0.35714285714285715, 0.0]
 [0.2142857142857143, 0.39285714285714285, 0.0]
 [0.1428571428571429, 0.42857142857142855, 0.0]
 [0.0714285714285714, 0.4642857142857143, 0.0]
 [0.0, 0.5, 0.0]

julia> c1 = colorant"rgb(255, 0, 0)"
RGB{N0f8}(1.0,0.0,0.0)

julia> c2 = colorant"rgb(0, 128, 0)"
RGB{N0f8}(0.0,0.502,0.0)

julia> range(colorant"rgb(255,0,0)", colorant"rgb(0,128,0)", length=15)
15-element Array{RGB{N0f8},1} with eltype RGB{FixedPointNumbers.N0f8}:
 RGB{N0f8}(1.0,0.0,0.0)
 RGB{N0f8}(0.929,0.035,0.0)
 RGB{N0f8}(0.859,0.071,0.0)
 RGB{N0f8}(0.784,0.11,0.0)
 RGB{N0f8}(0.714,0.145,0.0)
 RGB{N0f8}(0.643,0.18,0.0)
 RGB{N0f8}(0.573,0.216,0.0)
 RGB{N0f8}(0.502,0.251,0.0)
 RGB{N0f8}(0.427,0.286,0.0)
 RGB{N0f8}(0.357,0.322,0.0)
 RGB{N0f8}(0.286,0.357,0.0)
 RGB{N0f8}(0.216,0.392,0.0)
 RGB{N0f8}(0.141,0.431,0.0)
 RGB{N0f8}(0.071,0.467,0.0)
 RGB{N0f8}(0.0,0.502,0.0)

Visualization of the above color range can be obtained in VS Code by installing and running the Julia extension as follows.

Also, the return of range() can be used as a palette.

my_palette = range(colorant"rgb(255,0,0)", colorant"rgb(0,128,0)", length=15)

plot(rand(10, 15), palette = my_palette)

Environment

OS: Windows11
Version: Julia 1.9.4, Plots v1.39.0, Colors v0.12.10