数字影像在印片质量评价中的应用

Application of Digital Image to Measure Print Quality

影响印片质量的一个重要因素是均匀色面积上小面积光学密度的涨落,称为颗粒性。本文实验建立了利用平板扫描仪采集的数字影像进行颗粒性定量评价的方法。该方法建立了数字影像中红、绿、蓝色值与印片三色光学密度的关系,由三色数值标准偏差的平方加权组合形成颗粒性评价值。在两台扫描仪上分别选取三个不同的色调反差条件对灰、青、品、黄共12个颗粒样片进行了测试。每台扫描仪各自三个条件的颗粒性评价值具有很好的一致性;两台扫描仪上的颗粒性评价值线性相关;并将其与实际观测效果进行了比较。

An important aspect of poor print quality in color print is color density variation in micro areas,which is described as graininess.In this paper,a procedure to test graininess is described.The red,green and blue digital color values of a digital image,from a flatbed scanner,were related with optical densities,and their standard deviations were composed into graininess.The method was tested on 12 samples-gray,cyan,magenta and yellow-at three mid-tone contrasts on two scanners.The graininess values between different mid-tone contrasts were well consistent with each other,and that between two scanners were related lineally.Finally,the two sets of graininess values were compared with the visual ranking.