Optimal Filling of FG/BG Layers of Compound Document Images

In the basic 3-layer MRC model for compound document image coding, image pixels are separated into foreground and background layers. Pixels placed in the FG (BG) layer are called holes in the complementary layer and they can be assigned (filled) any values. This article proposes an optimal algorithm for hole filling. Our algorithm first divides the input into blocks to reduce complexity of the mask layer and then minimizes the sum of squares of Haar transform AC coefficients, which we show to be also equal to the square of DCT AC coefficients of the block. Experiments show that our method reduces the average energy by 30% more for the FG layer and by 20% more for BG layer blocks.