_color_shift($given, $ref1, $ref2, $target)
Shifts a given color, using a reference pair and a target blend color.
Note: this function is significantly different from the JS version, as it is written to match the blended images perfectly.
Constraint: if (ref2 == target + (ref1 - target) * delta) for some fraction delta then (return == target + (given - target) * delta).
Loose constraint: Preserve relative positions in saturation and luminance space.
File
- core/modules/color/color.module, line 681
- Allows users to change the color scheme of themes.
Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | function _color_shift($given, $ref1, $ref2, $target) { // We assume that ref2 is a blend of ref1 and target and find // delta based on the length of the difference vectors. // delta = 1 - |ref2 - ref1| / |white - ref1| $target = _color_unpack($target, TRUE); $ref1 = _color_unpack($ref1, TRUE); $ref2 = _color_unpack($ref2, TRUE); $numerator = 0; $denominator = 0; for ($i = 0; $i < 3; ++$i) { $numerator += ($ref2[$i] - $ref1[$i]) * ($ref2[$i] - $ref1[$i]); $denominator += ($target[$i] - $ref1[$i]) * ($target[$i] - $ref1[$i]); } $delta = ($denominator > 0) ? (1 - sqrt($numerator / $denominator)) : 0; // Calculate the color that ref2 would be if the assumption was true. for ($i = 0; $i < 3; ++$i) { $ref3[$i] = $target[$i] + ($ref1[$i] - $target[$i]) * $delta; } // If the assumption is not true, there is a difference between ref2 and ref3. // We measure this in HSL space. Notation: x' = hsl(x). $ref2 = _color_rgb2hsl($ref2); $ref3 = _color_rgb2hsl($ref3); for ($i = 0; $i < 3; ++$i) { $shift[$i] = $ref2[$i] - $ref3[$i]; } // Take the given color, and blend it towards the target. $given = _color_unpack($given, TRUE); for ($i = 0; $i < 3; ++$i) { $result[$i] = $target[$i] + ($given[$i] - $target[$i]) * $delta; } // Finally, we apply the extra shift in HSL space. // Note: if ref2 is a pure blend of ref1 and target, then |shift| = 0. $result = _color_rgb2hsl($result); for ($i = 0; $i < 3; ++$i) { $result[$i] = min(1, max(0, $result[$i] + $shift[$i])); } $result = _color_hsl2rgb($result); // Return hex color. return _color_pack($result, TRUE);} |
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