code: public function isSemitransparent()
  	{
  		if (!imageistruecolor($this->gdResource))
  		{
  			return false;
  		}
  
  		$width = imagesx($this->gdResource);
  		$height = imagesy($this->gdResource);
  
  		for ($x = 0; $x < $width; $x++)
  		{
  			for ($y = 0; $y < $height; $y++)
  			{
  				// Check if the pixel is semitransparent
  				$alpha = (imagecolorat($this->gdResource, $x, $y) >> 24) & 0x7F;
  
  				if ($alpha > 0 && $alpha < 127)
  				{
  					return true;
  				}
  			}
  		}
  
  		return false;
  	}
docs: Detect if the image contains semitransparent pixels
  
  @return boolean True if the image contains semitransparent pixels