https://purengom.com/2011/04/18/%ec%97%90%eb%b2%84%eb%85%b8%ed%8a%b8%ec%97%90%ec%84%9c-%ed%95%9c%ea%b5%ad%ec%96%b4-ocr%ec%9d%b4-%ec%95%88%eb%90%98%eb%8a%94-%ea%b2%bd%ec%9a%b0/