研究了墨点边缘发生羽化现象(非二值理想墨点)对印品光谱反射率的影响, 为色彩预测模型的理论研究提供一个新的思路。采用二维高斯函数模拟墨点表面的形态, 利用多重积分计算出墨点羽化后的体积, 根据体积的恒常性即羽化前后墨点体积相等, 推导出含边缘坡度因子σ的网点面积率以及含墨层相对厚度因子的油墨透射率, 由此建立了一个Clapper-Yule扩展模型。模型的数值模拟结果表明墨点边缘油墨铺展所导致的网点物理扩大, 增加了油墨对光的吸收, 从而降低了最终的光谱反射率。采用Clapper-Yule分程模型对颜色进行预测时需考虑墨点边缘羽化所带来的物理网点扩大, 该模型适用于彩色半色调印品的颜色预测与控制。

This paper investigates the effect of dot edge feathering (non-bilevel halftone image) on the spectral reflections, which provides a new angle of prediction model theory.The new extended Clapper-Yule model has been researched by introducing the two-dimensional Gaussian function to describe the surface of irregular ink dot, figuring out the volume of ink dot by multiple integral and deducing the dot area fraction related to edge gradient parameter σ and the ink layer transmittances related to ink relative thickness parameter, according to the equality of ink volume before and after the feathering.The numerical simulation of new model shows that the feathering of ink dot edge has caused the physical dot gain, the increases the absorption of light by the ink so decreases the ultimate spectral reflections.Using the branch-path Clapper-Yule model to predict the reflections must take the physical dot gain caused by the feathering of ink dot edge into account, and the new extended model can be applied to the color control of halftone images.