Text binarization in color documents

Abstract

This article presents a new method for the binarization of color document images. Initially, the colors of the document image are reduced to a small number using a new color reduction tech- nique. Specifically, this technique estimates the dominant colors and then assigns the original image colors to them in order that the back- ground and text components to become uniform. Each dominant color defines a color plane in which the connected components (CCs) are extracted. Next, in each color plane a CC filtering procedure is applied which is followed by a grouping procedure. At the end of this stage, blocks of CCs are constructed which are next redefined by obtaining the direction of connection (DOC) property for each CC. Using the DOC property, the blocks of CCs are classified as text or nontext. The identified text blocks are binarized properly using suita- ble binarization techniques, considering the rest of the pixels as background. The final result is a binary image which contains always black characters in white background independently of the original colors of each text block. The proposed document binarization approach can also be used for binarization of noisy color (or gray- scale) document images. Several experiments that confirm the effec- tiveness of the proposed technique are presented. V C 2007 Wiley