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| author | ThibG <thib@sitedethib.com> | 2020-08-02 18:47:44 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-08-02 18:47:44 +0200 |
| commit | 0ebc8d8626e3982696d1bb3876ec378a3bce81c9 (patch) | |
| tree | 12b9080bb30f26f94883bd27176b5d958b35d2f9 | |
| parent | 635b6a0f1af21bd4055f950930a681aa0a96535b (diff) | |
Fix thumbnail color extraction (#14464)
* Fix contrast calculation for thumbnail color extraction Luminance calculation was using 0-255 RGB values instead of 0-1 sRGB values, leading to incorrectly-computed contrast values. Since we use ColorDiff already, just use its XYZ colorspace conversion code to get the value. * Require at least 3:1 contrast for both accent and foreground colors * Lower required contrast for the accent color
| -rw-r--r-- | lib/paperclip/color_extractor.rb | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/lib/paperclip/color_extractor.rb b/lib/paperclip/color_extractor.rb index 44fe5ff1d..c8bb771a0 100644 --- a/lib/paperclip/color_extractor.rb +++ b/lib/paperclip/color_extractor.rb @@ -5,6 +5,7 @@ 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 @@ -26,8 +27,9 @@ module Paperclip foreground_palette.each do |color| distance = ColorDiff.between(background_color, color) + contrast = w3c_contrast(background_color, color) - if distance > max_distance + if distance > max_distance && contrast >= ACCENT_MIN_CONTRAST max_distance = distance max_distance_color = color end @@ -77,8 +79,8 @@ module Paperclip private def w3c_contrast(color1, color2) - luminance1 = (0.2126 * color1.r + 0.7152 * color1.g + 0.0722 * color1.b) + 0.05 - luminance2 = (0.2126 * color2.r + 0.7152 * color2.g + 0.0722 * color2.b) + 0.05 + luminance1 = color1.to_xyz.y * 0.01 + 0.05 + luminance2 = color2.to_xyz.y * 0.01 + 0.05 if luminance1 > luminance2 luminance1 / luminance2 |