Color dropout refers to the process of converting color form documents to black and white by removing the colors that are part of the blank form and maintaining only the information entered in the form. In this paper, no prior knowledge of the form type is assumed. Color dropout is performed by associating darker non-dropout colors with information that is entered in the form and needs to be preserved. The color dropout filter parameters include the color values of the non-dropout colors, e.g. black and blue, the distance metric, e.g. Euclidian, and the tolerances allowed around these colors. Color dropout is accomplished by converting pixels that have color within the tolerance sphere of the non-dropout colors to black and all others to white. This approach lends itself to high-speed hardware implementation with low memory requirements, such as an FPGA platform. Processing may be performed in RGB or a Luminance-Chrominance space, such as YCbCr. The color space transformation from RGB to YCbCr involves a matrix multiplication and the dropout filter implementation is similar in both cases. Results for color dropout processing in both RGB and YCbCr space are presented.
Department, Program, or Center
Chester F. Carlson Center for Imaging Science (COS)
Andreas E. Savakis, Christopher R. Brown, "Document processing for automatic color form dropout", Proc. SPIE 4472, Applications of Digital Image Processing XXIV, (7 December 2001); doi: 10.1117/12.449788; https://doi.org/10.1117/12.449788
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