system/Images/Handlers/BaseHandler.php
public function flatten(int $red = 255, int $green = 255, int $blue = 255)
	{
		$this->width  = $this->image->origWidth;
		$this->height = $this->image->origHeight;

		return $this->_flatten();
	}
public function flatten(int $red = 255, int $green = 255, int $blue = 255)
	{
		$this->width  = $this->image->origWidth;
		$this->height = $this->image->origHeight;

		return $this->_flatten();
	}
Flattens transparencies, default white background

@param integer $red
@param integer $green
@param integer $blue

@return mixed