# Return true if the difference between two colors # matches the W3C recommendations for readability # See http://www.wat-c.org/tools/CCA/1.1/ def colors_diff_ok? c1, c2 cont, bright = find_color_diff c1, c2 (cont > 500) && (bright > 125) # Acceptable diff according to w3c end # Return the contranst and brightness difference between two RGB values def find_color_diff c1, c2 r1, g1, b1 = break_color c1 r2, g2, b2 = break_color c2 cont_diff = (r1-r2).abs+(g1-g2).abs+(b1-b2).abs # Color contrast bright1 = (r1 * 299 + g1 * 587 + b1 * 114) / 1000 bright2 = (r2 * 299 + g2 * 587 + b2 * 114) / 1000 brt_diff = (bright1 - bright2).abs # Color brightness diff [cont_diff, brt_diff] end # Break a color into the R, G and B components def break_color rgb r = (rgb & 0xff0000) >> 16 g = (rgb & 0x00ff00) >> 8 b = rgb & 0x0000ff [r,g,b] end

http://devblog.famundo.com/articles/2006/06/14/finding-good-color-contrast

Finding Good Color Contrast

color

Ruby