Gd::resize

public function resize(Rectangle $source, Rectangle $destination)
{
	if ($this->resource === null)
	{
		return false;
	}

	$destinationWidth = $destination->getWidth();
	$destinationHeight = $destination->getHeight();

	if (($picture = imagecreatetruecolor($destinationWidth, $destinationHeight)))
	{
		$transparentColor = -1;

		imagealphablending($picture, false);

		if ($this->format == FileImage::FORMAT_PNG || $this->format == FileImage::FORMAT_WEBP)
		{
			$color = imagecolorallocatealpha($picture, 0, 0, 0, 127);
			imagefilledrectangle($picture, 0, 0, $destinationWidth, $destinationHeight, $color);
		}
		elseif ($this->format == FileImage::FORMAT_GIF)
		{
			// save transparency
			$transparentColor = $this->getTransparentColor();
			if ($transparentColor >= 0)
			{
				$rgb = imagecolorsforindex($this->resource, $transparentColor);
				$transparentColor = imagecolorallocatealpha($picture, $rgb['red'], $rgb['green'], $rgb['blue'], 127);
				imagefilledrectangle($picture, 0, 0, $destinationWidth, $destinationHeight, $transparentColor);
			}
		}

		if (imagecopyresampled($picture, $this->resource, 0, 0, $source->getX(), $source->getY(), $destinationWidth, $destinationHeight, $source->getWidth(), $source->getHeight()))
		{
			$this->clear();
			$this->resource = $picture;

			// restore transparency
			if ($transparentColor >= 0)
			{
				$this->restoreTransparency($transparentColor);
			}

			return true;
		}
	}
	return false;
}