Why the Lena image is the most widely used test image for all sorts of image processing algorithms?
First, the image contains a nice mixture of detail, flat
regions, shading, and texture that do a good job of testing various
image processing algorithms. It is a good test image! Second, the
Lena image is a picture of an attractive woman. It is not
surprising that the (mostly male) image processing research
community gravitated toward an image that they found
attractive.