目的 从噪声功率谱角度分析加网方式对图像质量产生的影响。方法 采用对比和验证试验方法， 分析平网区域和人物图像在不同网点结构下的噪声功率能量值与视觉效果的关系。结果 青、 品、黄、 黑等4色平网区域的噪声功率能量值在10%~100%之间有一定规律， 将人物图像平滑去噪后噪声能量值与视觉效果对比有一致性。结论 噪声功率谱可作为图像质量评价的综合分析指标， 平网区域不能作为评价印刷质量的唯一测试指标， 网点对图像产生的视觉效果与噪声功率谱能量值也应作为指标， 以全面有效地评价印刷品质量。

Objective In this paper, the noise power spectrum (NPS) was used to analyze the effects of screen rules on image quality. Methods The relationship between NPS and visual perceptual was analyzed under different screen structures, specially referring to dot area and portraits, using comparative and validating experimental methods. Results The rules for noise power energy in the range of 10%～100% were measured in Cyan, Magenta, Yellow and Black dot areas. The noise power data was consistent with visual perceptual after deleting the noise of the image. Conclusion NPS could be used as a comprehensive analysis index for evaluation and analysis of image quality, while flat screen area could not be used as the sole test index for evaluating printing quality. Visual perceptual and NPS data produced by printing dots should also be used as indices for comprehensive and effective evaluation of the quality of prints.