/**
* Returns a mask
*
* @param WideImage_Image $image
* @return WideImage_Image
*/
function execute($image)
{
$width = $image->getWidth();
$height = $image->getHeight();
$mask = WideImage_TrueColorImage::create($width, $height);
$mask->setTransparentColor(-1);
$mask->alphaBlending(false);
$mask->saveAlpha(false);
for ($i = 0; $i <= 255; $i++) {
$greyscale[$i] = ImageColorAllocate($mask->getHandle(), $i, $i, $i);
}
imagefilledrectangle($mask->getHandle(), 0, 0, $width, $height, $greyscale[255]);
$transparentColor = $image->getTransparentColor();
$alphaToGreyRatio = 255 / 127;
for ($x = 0; $x < $width; $x++) {
for ($y = 0; $y < $height; $y++) {
$color = $image->getColorAt($x, $y);
if ($color == $transparentColor) {
$rgba['alpha'] = 127;
} else {
$rgba = $image->getColorRGB($color);
}
imagesetpixel($mask->getHandle(), $x, $y, $greyscale[255 - round($rgba['alpha'] * $alphaToGreyRatio)]);
}
}
return $mask;
}
