ORL人脸库（英国）：剑桥大学，40人，每人10张照片，包括表情变化，微小姿态变化，20%以内的尺度变化。
可以直接使用本项目中的orl_face或从链接https://www.kaggle.com/datasets/kasikrit/att-database-of-faces 下载
Notes：
This directory contains a set of faces taken between April 1992 and April 1994 at the Olivetti Research Laboratory in Cambridge, UK.
There are 10 different images of 40 distinct subjects. For some of the subjects, the images were taken at different times, varying lighting slightly, facial expressions (open/closed eyes, smiling/non-smiling) and facial details (glasses/no-glasses). All the images are taken against a dark homogeneous background and the subjects are in up-right, frontal position (with tolerance for some side movement).
The files are in PGM format and can be conveniently viewed using the 'xv' program. The size of each image is 92x112, 8-bit grey levels.
The images are organised in 40 directories (one for each subject) named as: sX, where X indicates the subject number (between 1 and 40).
In each directory there are 10 different images of the selected subject named as: Y.pgm, where Y indicates which image for the specific subject (between 1 and 10).
When using these images, please give credit to Olivetti Research Laboratory. If you have any question, please email Ferdinando Samaria: fs@cam-orl.co.uk