public function filter($resource)
{
if (!is_resource($resource) || 'gd' !== get_resource_type($resource)) {
throw new \Exception('Resource must be given');
}
$width = imagesx($resource);
$height = imagesy($resource);
$greyscaleImageResource = imagecreatetruecolor($width, $height);
// prepare greyscale palette
for ($c = 0; $c < 256; $c++) {
$palette[$c] = imagecolorallocate($greyscaleImageResource, $c, $c, $c);
}
// set pixels
for ($y = 0; $y < $height; $y++) {
for ($x = 0; $x < $width; $x++) {
$rgb = imagecolorat($resource, $x, $y);
$grey = Yiq::getYFromRgbArray(Rgb::fromIntAsArray($rgb));
imagesetpixel($greyscaleImageResource, $x, $y, $palette[$grey]);
}
}
return $greyscaleImageResource;
}
public function testGreyscale()
{
$image = $this->_factory->openImage(__DIR__ . '/test.png');
$this->_factory->filterImage($image, 'greyscale');
$color = imagecolorat($image->getResource(), 0, 0);
$this->assertEquals(array(29, 29, 29), Rgb::fromIntAsArray($color));
$color = imagecolorat($image->getResource(), 0, 199);
$this->assertEquals(array(225, 225, 225), Rgb::fromIntAsArray($color));
}
