Asserts that the value of a literal is within the expected range
/**
* Adjusts the colour
* @param SassColour the colour to adjust
* @param SassNumber the amount to adust by
* @param boolean whether the amount is a proportion of the current value or
* the total range
* @param string the attribute to adjust
* @param boolean whether to decrease (false) or increase (true) the value of the attribute
* @param float minimum value the amount can be
* @param float maximum value the amount can bemixed
* @param string amount units
*/
private static function adjust($colour, $amount, $ofCurrent, $attribute, $op, $min, $max, $units = '')
{
SassLiteral::assertType($colour, 'SassColour');
SassLiteral::assertType($amount, 'SassNumber');
SassLiteral::assertInRange($amount, $min, $max, $units);
if (!is_bool($ofCurrent)) {
SassLiteral::assertType($ofCurrent, 'SassBoolean');
$ofCurrent = $ofCurrent->value;
}
$amount = $amount->value * ($attribute === 'alpha' && $ofCurrent && $units === '' ? 100 : 1);
return $colour->with(array($attribute => self::inRange($ofCurrent ? $colour->{$attribute} * (1 + $amount * ($op === self::INCREASE ? 1 : -1) / 100) : $colour->{$attribute} + $amount * ($op === self::INCREASE ? 1 : -1), $min, $max)));
}
/**
* Mixes two colours together.
* Takes the average of each of the RGB components, optionally weighted by the
* given percentage. The opacity of the colours is also considered when
* weighting the components.
* The weight specifies the amount of the first colour that should be included
* in the returned colour. The default, 50%, means that half the first colour
* and half the second colour should be used. 25% means that a quarter of the
* first colour and three quarters of the second colour should be used.
* For example:
* mix(#f00, #00f) => #7f007f
* mix(#f00, #00f, 25%) => #3f00bf
* mix(rgba(255, 0, 0, 0.5), #00f) => rgba(63, 0, 191, 0.75)
*
* @param SassColour The first colour
* @param SassColour The second colour
* @param float Percentage of the first colour to use
* @return new SassColour The mixed colour
* @throws SassScriptFunctionException If $colour1 or $colour2 is
* not a colour
*/
public static function mix($colour1, $colour2, $weight = '50%')
{
if (is_object($weight)) {
$weight = new SassNumber($weight);
}
SassLiteral::assertType($colour1, 'SassColour');
SassLiteral::assertType($colour2, 'SassColour');
SassLiteral::assertType($weight, 'SassNumber');
SassLiteral::assertInRange($weight, 0, 100, '%');
/*
* This algorithm factors in both the user-provided weight
* and the difference between the alpha values of the two colours
* to decide how to perform the weighted average of the two RGB values.
*
* It works by first normalizing both parameters to be within [-1, 1],
* where 1 indicates "only use colour1", -1 indicates "only use colour 0",
* and all values in between indicated a proportionately weighted average.
*
* Once we have the normalized variables w and a,
* we apply the formula (w + a)/(1 + w*a)
* to get the combined weight (in [-1, 1]) of colour1.
* This formula has two especially nice properties:
*
* * When either w or a are -1 or 1, the combined weight is also that number
* (cases where w * a == -1 are undefined, and handled as a special case).
*
* * When a is 0, the combined weight is w, and vice versa
*
* Finally, the weight of colour1 is renormalized to be within [0, 1]
* and the weight of colour2 is given by 1 minus the weight of colour1.
*/
$p = $weight->value / 100;
$w = $p * 2 - 1;
$a = $colour1->alpha - $colour2->alpha;
$w1 = (($w * $a == -1 ? $w : ($w + $a) / (1 + $w * $a)) + 1) / 2;
$w2 = 1 - $w1;
$rgb1 = $colour1->getRgb();
$rgb2 = $colour2->getRgb();
$rgba = array();
foreach ($rgb1 as $key => $value) {
$rgba[$key] = floor($value * $w1 + $rgb2[$key] * $w2);
}
// foreach
$rgba[] = floor($colour1->alpha * $p + $colour2->alpha * (1 - $p));
return new SassColour($rgba);
}
