先叠层甲。这是我写这帖子的根据。

众所周知，阿里云OSS可以进行图片的处理，而洛谷图床又是基于阿里云OSS的，所以我们可以根据官方文档进行一些奇怪的操作。

原图

【内切圆（友链神器）】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/circle,r_100/format,png

【圆角矩形】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/rounded-corners,r_30

【图片模糊】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/blur,r_10,s_10

【图片旋转】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/rotate,70

原图https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png

【等比缩放】https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png?x-oss-process=image/resize,m_lfit,h_170,w_225

【强制缩放】https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png?x-oss-process=image/resize,m_fixed,h_60,w_400

【pad缩放】（经测试剪贴板不支持color参数）https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png?x-oss-process=image/resize,m_pad,h_60,w_400,color_66CCFF

【图片水印】https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png?x-oss-process=image/watermark,t_80,g_center,text_SGVsbG8gV29ybGQ,color_66CCFF,rotate_40,fill_1

【图中图】https://cdn.luogu.com.cn/upload/image_hosting/ijnmco75.png?x-oss-process=image/watermark,g_center,image_dXBsb2FkL3VzZXJpY29uLzM5NTc1OC5wbmc=

【亮度调节】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/bright,50

【锐化】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/sharpen,300

【对比度调节】https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/contrast,-50

还有一些不常用的比如裁剪渐进显示啥的没列出来，有需要的可以自己查阅文档使用，切勿滥用。

另外也可以叠加使用。例如：

https://cdn.luogu.com.cn/upload/usericon/395758.png?x-oss-process=image/rounded-corners,r_30/rotate,70