ABSTRACT
Digital image through the digital halftone technology processing will introduce all
kinds of distortion. Therefore it will have important theoretical significance and
extensive application requirements to research halftone image quality assessment
algorithm used in the evaluation of the images which is caused by the various
application algorithm. Halftone image quality assessment includes subjective evaluation
and objective evaluation. Because the human eyes are the final receptors of image, so
subjective evaluation is considered to be the most direct and accurate method of visual
perception. But due to the objective condition and subjective feelings and the viewers’
factors, subjective evaluation results are often not enough stability and do not facilitate
image system integration and implementation. So it is especially critical to find an
objective evaluation which is able to approach the subjective evaluation results as the
basis of image quality evaluation and designing and improving the image system.
The main research contents of this paper include:
1. Current quality assessment algorithms for halftone image are researched, and its
characteristics and shortages provide theoretical basis to design the improved algorithm;
2. Combining the feature of halftone image, the evaluation algorithm based on
halftone image feature is proposed;
3. Studying the characteristics of human visual system and wavelet transform, I get
that the multi-channel characteristic of human visual perception is matched with the
wavelet decomposition which provide basis for the new algorithm using wavelet
transform to simulate the features of human eyes;
4. A new quality evaluation algorithm based on the halftone characteristics and
quality-concerned factors is proposed, and MATLAB designs the algorithm program;
5. Using the evaluation indexes to analysis validity of the proposed algorithm.
The main innovations are as follows:
Three kinds of algorithms are studied and their shortages to evaluate halftone
image are pointed out. And an improved algorithm based on halftone
characteristic is put forward.
I analyze three main factors affecting the quality of the image and combining
halftone image characteristic and the multi-scale analysis of wavelet transform,
HIQA is put forward.
Objective evaluation of the halftone image has an important practical value and