base64编码转图片格式
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title></head><body><img src="data:image/png;base64,XXX" alt=""></body></html>
备注：文中XXX是放置图片编码的地方
