56 lines
1.3 KiB
Elixir
56 lines
1.3 KiB
Elixir
defmodule Liliform.Colorhash do
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@moduledoc """
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Given a string returns HSL color.
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"""
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alias Freedive.Features
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require Logger
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@seed "zeni"
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@default_color {0, 0, 0}
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@doc """
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Given a string returns HSL color as a CSS string.
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"""
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def hsl(input) do
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{hue, saturation, lightness} = hsl(input, raw: true)
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"hsl(#{hue}, #{saturation}%, #{lightness}%)"
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end
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@doc """
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Given a string returns HSL color.
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"""
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def hsl(input, raw: true) do
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if Features.enabled?(:colorhash) do
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input = String.downcase(input) <> @seed
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hash = :erlang.phash2(input, 2_147_483_647)
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hue = calculate_hue(hash)
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saturation = 80 + rem(hash, 21)
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lightness = 30 + rem(hash, 31)
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{hue, saturation, lightness}
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else
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@default_color
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end
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end
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@doc """
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Calculates hue avoiding low contrast colors.
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"""
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def calculate_hue(hash) do
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base_hue = rem(hash, 360)
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# Ranges to exclude (yellow to light green, cyan)
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excluded_ranges = [
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# yellow
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{40, 80},
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# cyan
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{175, 185}
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]
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# Adjust the hue to skip over excluded ranges
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Enum.reduce(excluded_ranges, base_hue, fn {start, stop}, acc_hue ->
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if acc_hue >= start and acc_hue <= stop, do: stop + (acc_hue - start + 1), else: acc_hue
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end)
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end
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end
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