/**
* Modify image opacity. To work correctly image must be saved in PNG or GIF format.
*
* @param mixed $alpha Default is float in range [0-1], however setting omega allows for custom input range.
* @param integer $omega Adjustment sensitivity. User may enter +/- this value and the output will be normalized for safe function usage
* @return mixed On success, current object to allow function chaining. False otherwise.
*/
public function alpha($alpha = 0.5, $omega = false)
{
# Normalize input if desired.
if ($omega !== false) {
$alpha = Number::normalize($alpha, 0, 1, $omega);
}
# Convert CSS alpha to GD ranges
$alpha = Color::alpha2gd(Number::minmax($alpha, 0, 1));
# Set image boundaries
$width = imagesx($this->img);
$height = imagesy($this->img);
for ($x = 0; $x < $width; $x++) {
for ($y = 0; $y < $height; $y++) {
# Extract Bits
$rgb = imagecolorat($this->img, $x, $y);
$r = $rgb >> 16 & 0xff;
$g = $rgb >> 8 & 0xff;
$b = $rgb & 0xff;
$a = ($rgb & 0xff000000) >> 24;
# Modify alpha
$a += $alpha;
# Boundary checks
$a = $a > 127 ? 127 : ($a < 0 ? 0 : $a);
# Inject pixel with alpha
if (!imagesetpixel($this->img, $x, $y, imagecolorallocatealpha($this->img, $r, $g, $b, $a))) {
return false;
}
}
}
# Apply filter. On success update filename and return current object for function chaining, false on error.
return $this->update(__FUNCTION__, func_get_args());
}
