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# frozen_string_literal: true
require 'mime/types/columnar'
module Paperclip
class ColorExtractor < Paperclip::Processor
MIN_CONTRAST = 3.0
ACCENT_MIN_CONTRAST = 2.0
FREQUENCY_THRESHOLD = 0.01
def make
depth = 8
# Determine background palette by getting colors close to the image's edge only
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)
# Determine foreground palette from the whole image
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)
background_color = background_palette.first || foreground_palette.first
foreground_colors = []
return @file if background_color.nil?
max_distance = 0
max_distance_color = nil
foreground_palette.each do |color|
distance = ColorDiff.between(background_color, color)
contrast = w3c_contrast(background_color, color)
if distance > max_distance && contrast >= ACCENT_MIN_CONTRAST
max_distance = distance
max_distance_color = color
end
end
foreground_colors << max_distance_color unless max_distance_color.nil?
max_distance = 0
max_distance_color = nil
foreground_palette.each do |color|
distance = ColorDiff.between(background_color, color)
contrast = w3c_contrast(background_color, color)
if distance > max_distance && contrast >= MIN_CONTRAST && !foreground_colors.include?(color)
max_distance = distance
max_distance_color = color
end
end
foreground_colors << max_distance_color unless max_distance_color.nil?
# If we don't have enough colors for accent and foreground, generate
# new ones by manipulating the background color
(2 - foreground_colors.size).times do |i|
foreground_colors << lighten_or_darken(background_color, 35 + (i * 15))
end
# We want the color with the highest contrast to background to be the foreground one,
# and the one with the highest saturation to be the accent one
foreground_color = foreground_colors.max_by { |rgb| w3c_contrast(background_color, rgb) }
accent_color = foreground_colors.max_by { |rgb| rgb_to_hsl(rgb.r, rgb.g, rgb.b)[1] }
meta = {
colors: {
background: rgb_to_hex(background_color),
foreground: rgb_to_hex(foreground_color),
accent: rgb_to_hex(accent_color),
},
}
attachment.instance.file.instance_write(:meta, (attachment.instance.file.instance_read(:meta) || {}).merge(meta))
@file
end
private
def w3c_contrast(color1, color2)
luminance1 = color1.to_xyz.y * 0.01 + 0.05
luminance2 = color2.to_xyz.y * 0.01 + 0.05
if luminance1 > luminance2
luminance1 / luminance2
else
luminance2 / luminance1
end
end
# rubocop:disable Naming/MethodParameterName
def rgb_to_hsl(r, g, b)
r /= 255.0
g /= 255.0
b /= 255.0
max = [r, g, b].max
min = [r, g, b].min
h = (max + min) / 2.0
s = (max + min) / 2.0
l = (max + min) / 2.0
if max == min
h = 0
s = 0 # achromatic
else
d = max - min
s = l >= 0.5 ? d / (2.0 - max - min) : d / (max + min)
case max
when r
h = (g - b) / d + (g < b ? 6.0 : 0)
when g
h = (b - r) / d + 2.0
when b
h = (r - g) / d + 4.0
end
h /= 6.0
end
[(h * 360).round, (s * 100).round, (l * 100).round]
end
def hue_to_rgb(p, q, t)
t += 1 if t.negative?
t -= 1 if t > 1
return (p + (q - p) * 6 * t) if t < 1 / 6.0
return q if t < 1 / 2.0
return (p + (q - p) * (2 / 3.0 - t) * 6) if t < 2 / 3.0
p
end
def hsl_to_rgb(h, s, l)
h /= 360.0
s /= 100.0
l /= 100.0
r = 0.0
g = 0.0
b = 0.0
if s.zero?
r = l.to_f
g = l.to_f
b = l.to_f # achromatic
else
q = l < 0.5 ? l * (s + 1) : l + s - l * s
p = 2 * l - q
r = hue_to_rgb(p, q, h + 1 / 3.0)
g = hue_to_rgb(p, q, h)
b = hue_to_rgb(p, q, h - 1 / 3.0)
end
[(r * 255).round, (g * 255).round, (b * 255).round]
end
# rubocop:enable Naming/MethodParameterName
def lighten_or_darken(color, by)
hue, saturation, light = rgb_to_hsl(color.r, color.g, color.b)
light = begin
if light < 50
[100, light + by].min
else
[0, light - by].max
end
end
ColorDiff::Color::RGB.new(*hsl_to_rgb(hue, saturation, light))
end
def palette_from_histogram(result, quantity)
frequencies = result.scan(/([0-9]+)\:/).flatten.map(&:to_f)
hex_values = result.scan(/\#([0-9A-Fa-f]{6,8})/).flatten
total_frequencies = frequencies.reduce(&:+).to_f
frequencies.map.with_index { |f, i| [f / total_frequencies, hex_values[i]] }
.sort_by { |r| -r[0] }
.reject { |r| r[1].size == 8 && r[1].end_with?('00') }
.map { |r| ColorDiff::Color::RGB.new(*r[1][0..5].scan(/../).map { |c| c.to_i(16) }) }
.slice(0, quantity)
end
def rgb_to_hex(rgb)
'#%02x%02x%02x' % [rgb.r, rgb.g, rgb.b]
end
end
end