问一个文件上传保存格式问题？
我对网站中图片上传有几个疑问？
我对上传图片保存的方式是按照原后缀名直接保存的，php处理文件上传时只是将上传的零时文件拷贝过来而已，所以格式还是保持原上传的格式例如
原图.jpg上传后可能会被保存为13141520.jpg这样的。
我如果想保存为别的后缀可以吗？
会改变源文件吗，原MD5会改变吗，有损害吗，会导致格式出错吗？
直接改变后缀保存就可以还是要编码啊，比如jpg转码成png，怎么做啊？
本地操作系统中这样随便改变一张图片的后缀保存好像不会出问题照样打得开啊，谁能跟我解释下文件名这个东西？
谢谢了^_^
回复内容：
我对网站中图片上传有几个疑问？
我对上传图片保存的方式是按照原后缀名直接保存的，php处理文件上传时只是将上传的零时文件拷贝过来而已，所以格式还是保持原上传的格式例如
原图.jpg上传后可能会被保存为13141520.jpg这样的。
我如果想保存为别的后缀可以吗？
会改变源文件吗，原MD5会改变吗，有损害吗，会导致格式出错吗？
直接改变后缀保存就可以还是要编码啊，比如jpg转码成png，怎么做啊？
本地操作系统中这样随便改变一张图片的后缀保存好像不会出问题照样打得开啊，谁能跟我解释下文件名这个东西？
谢谢了^_^
1，可以保存其他格式，实际上文件的格式是没有变的，因此md5值也不会变
2，如果你想改为其他格式的图片，必须经过转码操作，20M以下的图片支持同步操作，即：
url?imageMogr2/format/..
例：
jpg格式的图片：
http://7xmz3r.com5.z0.glb.qiniucdn.com/20151203%2FFi85UYGcE_Vs1aJ0NcRt9iul_ISW.jfif-tbnl
转码为webp：
http://7xmz3r.com5.z0.glb.qiniucdn.com/20151203%2FFi85UYGcE_Vs1aJ0NcRt9iul_ISW.jfif-tbnl?imageMogr2/format/webp
如图所示就可以转换为webp格式
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