For ocular fundus images (OFIs), geometric distortion due to taking pictures at oblique visuai points and gray level distortion due to leakage of fluorescein and so on are almost unavoidable.

• 对于眼底图像,由于不在正视点取像造成的几何畸变和由于荧光素从血管壁渗漏等造成的灰度畸变,几乎是不可避免的。