Created
July 19, 2016 19:28
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Simple and very accurate function to check the contrast of 2 RGB colors. (uses YIQ weights)
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| /** | |
| * Measures the visual contrast of 2 RGB colors. | |
| * | |
| * NOTE: most colors do not have a 100% contrasting opposite, but all colors | |
| * do have a contrasting opposite that is at least 50%. | |
| * | |
| * @param array $rgb1 The first color, array where offsets 'r', 'g', & 'b' contain their respective values. | |
| * @param array $rgb2 The second color, array where offsets 'r', 'g', & 'b' contain their respective values. | |
| * @return float The visual contrast as a percentage (e.g. 12.345) | |
| */ | |
| function rgb_contrast($rgb1, $rgb2) { | |
| $r = (max($rgb1['r'], $rgb2['r']) - min($rgb1['r'], $rgb2['r'])) * 299; | |
| $g = (max($rgb1['g'], $rgb2['g']) - min($rgb1['g'], $rgb2['g'])) * 587; | |
| $b = (max($rgb1['b'], $rgb2['b']) - min($rgb1['b'], $rgb2['b'])) * 114; | |
| // Sum => Average => Convert to percentage | |
| return ($r + $g + $b) / 1000 / 2.55; | |
| } |
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Please note that the only good way to check 2 colors perceived contrast is with the RGB spectrum. This because human eyes work by using red, blue, and green sensory cones to distinguish colors.