/**
* Determine best match to over/underlay a defined color.
*
* Calculates UCCIR 601 luma of the entered color and returns a black or
* white color to ensure readibility.
*
* @see http://en.wikipedia.org/wiki/Luma_video
*/
public static function matchLuma($rgba, $soft = FALSE)
{
$rgb = Unicode::substr($rgba, 0, 7);
list($r, $g, $b) = array_values(Color::hexToRgb($rgb));
$luma = 1 - (0.299 * $r + 0.587 * $g + 0.114 * $b) / 255;
if ($luma < 0.5) {
// Bright colors - black.
$d = 0;
} else {
// Dark colors - white.
$d = 255;
}
return Color::rgbToHex(array($d, $d, $d));
}
/**
* Form element validation handler for #type 'color'.
*/
public static function validateColor(&$element, FormStateInterface $form_state, &$complete_form)
{
$value = trim($element['#value']);
// Default to black if no value is given.
// @see http://www.w3.org/TR/html5/number-state.html#color-state
if ($value === '') {
$form_state->setValueForElement($element, '#000000');
} else {
// Try to parse the value and normalize it.
try {
$form_state->setValueForElement($element, ColorUtility::rgbToHex(ColorUtility::hexToRgb($value)));
} catch (\InvalidArgumentException $e) {
$form_state->setError($element, t('%name must be a valid color.', array('%name' => empty($element['#title']) ? $element['#parents'][0] : $element['#title'])));
}
}
}
/**
* Gets the color set for transparency in GIF images.
*
* @return string|null
* A color string like '#rrggbb', or NULL if not set or not relevant.
*/
public function getTransparentColor()
{
if (!$this->getResource() || $this->getType() != IMAGETYPE_GIF) {
return NULL;
}
// Find out if a transparent color is set, will return -1 if no
// transparent color has been defined in the image.
$transparent = imagecolortransparent($this->getResource());
if ($transparent >= 0) {
// Find out the number of colors in the image palette. It will be 0 for
// truecolor images.
$palette_size = imagecolorstotal($this->getResource());
if ($palette_size == 0 || $transparent < $palette_size) {
// Return the transparent color, either if it is a truecolor image
// or if the transparent color is part of the palette.
// Since the index of the transparent color is a property of the
// image rather than of the palette, it is possible that an image
// could be created with this index set outside the palette size.
// (see http://stackoverflow.com/a/3898007).
$rgb = imagecolorsforindex($this->getResource(), $transparent);
unset($rgb['alpha']);
return Color::rgbToHex($rgb);
}
}
return NULL;
}
/**
* Tests Color::rgbToHex().
*
* @param string $value
* The rgb color value.
* @param string $expected
* The expected hex color value.
*
* @dataProvider providerTestRbgToHex
*/
public function testRgbToHex($value, $expected)
{
$this->assertSame($expected, Color::rgbToHex($value));
}
