Image Rectification based on Flash and No-flash Image Pairs

Digitizing documents or books by digital cameras are preferred instead of flatbed scanners due to convenience and fast response. However, camera-captured document images have many problems, such as specular reflection, non-uniform illumination, and perspective and geometric distortions. In order to solve these defects, many methods have been proposed in the last decades. Nevertheless, they can only overcome one or two of the drawbacks mentioned above each time.
This thesis proposes an integrated system to deal with the three problems based on flash and no-flash image pairs taken at the same angle. Flash and no-flash image pairs are used to compose specular reflection removal images. And then an image enhancement method is applied to remove non-uniform illumination. Finally, boundary interpolation provides an effective solution to perspective and geometric distortions.
The experimental results show that our system can restore the frontal-flat views of the documents and remove specular reflection and non-uniform illumination without any specific hardwares or user inputs.