Restoration of semi-transparent blotches in damaged texts, manuscripts, and images through localized, logarithmic image enhancement

Great libraries of historic texts, manuscripts, and images are available at this time. The information contained in these documents will be of critical importance in documenting the history of humanity in the years to come. However, many of these documents are degrading for a variety of reasons, including semi-transparent blotches. Current restoration techniques are either chemical in nature or involve significant user interaction through a desktop computer. Due to operator costs, either method is too expensive for the large quantity of information that needs to be preserved. Automated blotch removal algorithms exist, however they all have severe limitations: Some mechanisms only work on text and not images while others leave edges around the blotch or blur the image within the blotch. This paper introduces an automated Local Logarithmic Restoration Algorithm to restore semi-transparent blotches in a variety of documents. Intensive computer simulations show: (1) the new algorithm outperforms competing algorithms by providing better local contrast preservation, expanded saturation reduction capabilities, and improved edge removal; and (2) it is a flexible and practical algorithm for batch restoration many pages of text, manuscripts, or images.