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191 lines
5.6 KiB
191 lines
5.6 KiB
# frozen_string_literal: true
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require 'mime/types/columnar'
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module Paperclip
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class ColorExtractor < Paperclip::Processor
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MIN_CONTRAST = 3.0
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ACCENT_MIN_CONTRAST = 2.0
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FREQUENCY_THRESHOLD = 0.01
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def make
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depth = 8
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# Determine background palette by getting colors close to the image's edge only
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background_palette = palette_from_histogram(convert(':source -alpha set -gravity Center -region 75%x75% -fill None -colorize 100% -alpha transparent +region -format %c -colors :quantity -depth :depth histogram:info:', source: File.expand_path(@file.path), quantity: 10, depth: depth), 10)
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# Determine foreground palette from the whole image
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foreground_palette = palette_from_histogram(convert(':source -format %c -colors :quantity -depth :depth histogram:info:', source: File.expand_path(@file.path), quantity: 10, depth: depth), 10)
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background_color = background_palette.first || foreground_palette.first
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foreground_colors = []
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return @file if background_color.nil?
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max_distance = 0
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max_distance_color = nil
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foreground_palette.each do |color|
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distance = ColorDiff.between(background_color, color)
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contrast = w3c_contrast(background_color, color)
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if distance > max_distance && contrast >= ACCENT_MIN_CONTRAST
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max_distance = distance
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max_distance_color = color
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end
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end
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foreground_colors << max_distance_color unless max_distance_color.nil?
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max_distance = 0
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max_distance_color = nil
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foreground_palette.each do |color|
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distance = ColorDiff.between(background_color, color)
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contrast = w3c_contrast(background_color, color)
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if distance > max_distance && contrast >= MIN_CONTRAST && !foreground_colors.include?(color)
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max_distance = distance
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max_distance_color = color
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end
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end
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foreground_colors << max_distance_color unless max_distance_color.nil?
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# If we don't have enough colors for accent and foreground, generate
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# new ones by manipulating the background color
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(2 - foreground_colors.size).times do |i|
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foreground_colors << lighten_or_darken(background_color, 35 + (i * 15))
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end
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# We want the color with the highest contrast to background to be the foreground one,
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# and the one with the highest saturation to be the accent one
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foreground_color = foreground_colors.max_by { |rgb| w3c_contrast(background_color, rgb) }
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accent_color = foreground_colors.max_by { |rgb| rgb_to_hsl(rgb.r, rgb.g, rgb.b)[1] }
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meta = {
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colors: {
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background: rgb_to_hex(background_color),
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foreground: rgb_to_hex(foreground_color),
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accent: rgb_to_hex(accent_color),
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},
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}
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attachment.instance.file.instance_write(:meta, (attachment.instance.file.instance_read(:meta) || {}).merge(meta))
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@file
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end
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private
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def w3c_contrast(color1, color2)
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luminance1 = color1.to_xyz.y * 0.01 + 0.05
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luminance2 = color2.to_xyz.y * 0.01 + 0.05
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if luminance1 > luminance2
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luminance1 / luminance2
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else
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luminance2 / luminance1
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end
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end
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# rubocop:disable Naming/MethodParameterName
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def rgb_to_hsl(r, g, b)
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r /= 255.0
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g /= 255.0
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b /= 255.0
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max = [r, g, b].max
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min = [r, g, b].min
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h = (max + min) / 2.0
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s = (max + min) / 2.0
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l = (max + min) / 2.0
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if max == min
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h = 0
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s = 0 # achromatic
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else
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d = max - min
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s = l >= 0.5 ? d / (2.0 - max - min) : d / (max + min)
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case max
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when r
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h = (g - b) / d + (g < b ? 6.0 : 0)
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when g
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h = (b - r) / d + 2.0
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when b
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h = (r - g) / d + 4.0
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end
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h /= 6.0
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end
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[(h * 360).round, (s * 100).round, (l * 100).round]
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end
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def hue_to_rgb(p, q, t)
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t += 1 if t.negative?
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t -= 1 if t > 1
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return (p + (q - p) * 6 * t) if t < 1 / 6.0
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return q if t < 1 / 2.0
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return (p + (q - p) * (2 / 3.0 - t) * 6) if t < 2 / 3.0
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p
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end
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def hsl_to_rgb(h, s, l)
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h /= 360.0
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s /= 100.0
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l /= 100.0
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r = 0.0
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g = 0.0
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b = 0.0
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if s.zero?
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r = l.to_f
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g = l.to_f
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b = l.to_f # achromatic
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else
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q = l < 0.5 ? l * (s + 1) : l + s - l * s
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p = 2 * l - q
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r = hue_to_rgb(p, q, h + 1 / 3.0)
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g = hue_to_rgb(p, q, h)
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b = hue_to_rgb(p, q, h - 1 / 3.0)
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end
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[(r * 255).round, (g * 255).round, (b * 255).round]
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end
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# rubocop:enable Naming/MethodParameterName
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def lighten_or_darken(color, by)
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hue, saturation, light = rgb_to_hsl(color.r, color.g, color.b)
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light = begin
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if light < 50
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[100, light + by].min
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else
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[0, light - by].max
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end
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end
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ColorDiff::Color::RGB.new(*hsl_to_rgb(hue, saturation, light))
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end
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def palette_from_histogram(result, quantity)
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frequencies = result.scan(/([0-9]+)\:/).flatten.map(&:to_f)
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hex_values = result.scan(/\#([0-9A-Fa-f]{6,8})/).flatten
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total_frequencies = frequencies.reduce(&:+).to_f
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frequencies.map.with_index { |f, i| [f / total_frequencies, hex_values[i]] }
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.sort_by { |r| -r[0] }
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.reject { |r| r[1].size == 8 && r[1].end_with?('00') }
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.map { |r| ColorDiff::Color::RGB.new(*r[1][0..5].scan(/../).map { |c| c.to_i(16) }) }
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.slice(0, quantity)
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end
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def rgb_to_hex(rgb)
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'#%02x%02x%02x' % [rgb.r, rgb.g, rgb.b]
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end
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end
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end
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