Francesca Martinelli and Anna Tonazzini
Color Document Restoration, Color Space Transformations, Contrast Enhancement, See-Through Removal, Wavelet Filtering
Frequent degradation in ancient manuscripts are see-through interferences and poor contrast between the written text and the background, which compromise or make difficult their legibility. Normally, these manuscripts appear colored due to ageing factors such as yellowing of the paper or diffusion and oxidation of the ink chemical components. Very often, these degradations produce monochrome manuscripts where a single color is predominant. Scholars and archivists are nowadays interested in digital image processing techniques to improve their readability, but might desire to preserve their general appearance as well, since this is a mark of their history. In this paper we propose very simple and fast procedures to remove interferences and enhance the contrast in monochrome manuscripts while preserving their color. These procedures are based on the enhancement of the only luminance component Y of the YCbCr representation of the original RGB manuscript image, and make also use of the CMYK representation. Our method favorably compares with tools of commercial software packages for image manipulation, which, furthermore, often requires expert user intervention.
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