Survey on Restoration of Degraded Document using Different Thresholding Techniques.

Documents are degraded normally by the disturbance caused in the background . These are known as bleed-through effect, (ie) a pattern that interferes with the main text due to seeping of ink from the reverse side. These degradations must be removed to improve human or automatic readability. Degraded documents will have background noise ,changes in contrast and illumination ,so it is best to use local thresholding methods to restore foreground. Comparative study on some local adaptive thresholding methods such as niblack, sauvola, wolf and feng are done and analyse its quality over different images. The quality of the image is measured in terms of PSNR and correlation