利用虚光蒙版提高图像清晰度及其评价方法研究

Research of Improving Image Definition with Unsharp Masking and Evaluation Method

图像的清晰度包含锐度、反差两个方面。在印前系统中,对图像反差的调整是图像处理的重要环节。本研究采用创建虚光蒙版的方法增大局部反差,使图像清晰度提高,并在图像不失真的前提下对其进行锐化,增强反差效果。此外,研究了基于MT F的图像清晰度评价方法,在Matlah中编程绘制出多种情况下的MTF曲线,并以MTF曲线和坐标轴所围面积为数据,对图像清晰度提高程度进行量化,比较它们相对原稿的提高幅度;结合主观评价实验,验证了此方法的准确性。结果表明,面积越大图像清晰度越高。此研究结果对印前数字图像处理有一定的指导性。

Image definition includes two factors： acutance, contrast and resolution. Adjusting image contrast is a important node in image processing. In this paper, a method of creating unsharp masking was used to increase local contrast, which improved image definition. Then image was sharpened under the condition that the image was not fuzzy to enhance the contrast effect. Moreover, the method of evaluating image definition based on MTF was studied. After drawing MTF curves in Matlab, the area that MTF curves surround axes is the data to measure the increased effect of image definition and the im proving rate compared with manuscript was got. Finally, a subjective assessment was adopted to prove its accuracy. The resuits showed that the more area is, the more image definition is, which will conduct the digital image processing in prepress