Advanced digital halftoning algorithms: Printer model, color, and compression
In this thesis, we address three advanced digital halftoning topics: printer model, color, and compression. First we explore the printer model-based approach in order to enhance the quality of the print. While a large literature addresses model-based halftoning for electrophotographic (EP) printers, little work has been done on model-based halftoning for inkjet (IJ) printers, which have their own unique artifacts. Therefore, we develop a stochastic printer model based on the dot statistics of the IJ printer. This printer model is then incorporated into two state-of-the-art halftoning algorithms, direct binary search (DBS) and tone-dependent error diffusion (TDED). Next we propose color design criteria for uniform color textures, and present a new colorant-based color halftoning technique, which meets these criteria. The basic idea behind our color halftoning method is to control the quality of each colorant texture separately along with the total dot distribution. In order to achieve this, we first set the total dot arrangement and then color the dots optimally without altering the total dot arrangement. This corresponds to a constrained optimization problem, and we solve this via the swap-only DBS heuristic. Finally, we present a combined halftoning and compression work, which achieves high quality halftones and compression ratios comparable to JBIG's with much more simpler encoding and decoding schemes. In our approach, the input continuous-tone image is halftoned with constraints in a controlled manner, so that we can decrease the entropy of the halftone while maintaining the level of image quality still very high. ^
Major Professor: Jan P. Allebach, Purdue University.
Engineering, Electronics and Electrical