https://purengom.com/2011/11/01/pixelmator%ec%9d%98-%ed%9e%90%eb%a7%81-%ed%88%b4-%eb%8f%99%ec%98%81%ec%83%81%ed%8f%ac%ed%86%a0%ec%83%b5%ea%b3%bc-%eb%b9%84%ea%b5%90/