[画圆形头像](Canvas/%E7%94%BB%E5%9C%86%E5%BD%A2%E5%A4%B4%E5%83%8F.md) [计算字符串宽度](Canvas/%E8%AE%A1%E7%AE%97%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%AE%BD%E5%BA%A6.md)