An image processing device includes an image acquisition module, a memory module, and an image signal processing module, for performing an image enlargement and enhancement. The image acquisition module sequentially reads in an image block, including a unit pixel matrix and an exterior pixel matrix, wherein each pixel matrix includes a plurality of pixels and each pixel is associated with a parameter. The memory module stores a plurality of predefined edge patterns. The image signal processing module compares a loaded image block with predefined edge patterns, and determines if it is an edge block. Then, the image signal processing module further classifies its pixels into two groups, and calculates a continuous separating boundary between the two groups. Finally, the image signal processing module enlarges an edge block by placing new pixels inside its unit pixel matrix, wherein the new pixel parameters are extrapolated from the two classified pixel groups to maintain a sharp edge boundary. For those that are not edge blocks, interpolations are performed by the image signal processing module to derive smooth enlargements.