https://purengom.com/2011/05/13/%eb%a7%a5%ec%97%90%ec%84%9c-%ec%97%90%eb%b2%84%eb%85%b8%ed%8a%b8-ocr-%ec%9d%b8%ec%8b%9d%ec%9d%b4-%ec%95%88%eb%90%98%eb%8a%94-%ea%b2%bd%ec%9a%b0-2/