Gd::drawImageWatermark

public function drawImageWatermark(ImageWatermark $watermark)
{
	if ($this->resource === null)
	{
		return false;
	}

	if (($image = $this->loadWatermark($watermark)) === null)
	{
		return false;
	}

	$width = $this->getWidth();
	$height = $this->getHeight();

	$watermarkWidth = $image->getWidth();
	$watermarkHeight = $image->getHeight();

	$position = new Rectangle($watermarkWidth, $watermarkHeight);

	$watermark->alignPosition($width, $height, $position);

	$watermarkX = $position->getX();
	$watermarkY = $position->getY();

	$watermarkAlpha = $watermark->getAlpha();
	$repeat = ($watermark->getMode() == ImageWatermark::MODE_REPEAT);

	for ($y = 0; $y < $watermarkHeight; $y++)
	{
		for ($x = 0; $x < $watermarkWidth; $x++)
		{
			$posY = $watermarkY + $y;
			while (true)
			{
				$posX = $watermarkX + $x;
				while (true)
				{
					$alpha = $watermarkAlpha;

					$mainRgb = imagecolorsforindex($this->resource, imagecolorat($this->resource, $posX, $posY));
					$watermarkRgb = imagecolorsforindex($image->resource, imagecolorat($image->resource, $x, $y));

					if ($watermarkRgb['alpha'] == 127)
					{
						$pixel = $mainRgb;
					}
					else
					{
						if ($watermarkRgb['alpha'])
						{
							$alpha = round((( 127 - $watermarkRgb['alpha']) / 127), 2);
							$alpha = $alpha * $watermarkAlpha;
						}

						$pixel = [];
						foreach (['red', 'green', 'blue', 'alpha'] as $k)
						{
							$pixel[$k] = round(($mainRgb[$k] * (1 - $alpha)) + ($watermarkRgb[$k] * $alpha));
						}
					}

					$color = imagecolorexactalpha($this->resource, $pixel['red'], $pixel['green'], $pixel['blue'], $pixel['alpha']);
					if ($color == -1)
					{
						$color = imagecolorallocatealpha($this->resource, $pixel['red'], $pixel['green'], $pixel['blue'], $pixel['alpha']);
						if ($color === false)
						{
							$color = imagecolorclosestalpha($this->resource, $pixel['red'], $pixel['green'], $pixel['blue'], $pixel['alpha']);
						}
					}

					imagesetpixel($this->resource, $posX, $posY, $color);

					$posX += $watermarkWidth;

					if (!$repeat || $posX > $width)
					{
						break;
					}
				}

				$posY += $watermarkHeight;

				if (!$repeat || $posY > $height)
				{
					break;
				}
			}
		}
	}

	$image->clear();

	return true;
}