彩色数字图像色差计算方法的研究

用5幅ISO SCID图像在EIZO CG19显示器上分别进行了两组图像色差等级评价实验。两组实验分别在室内自然照明环境和标准灯箱中进行,用目视评价实验数据检验并优化彩色图像色差的计算公式。用CIELAB、CIEDE2000、CIE94和CMC色差公式对第一组实验数据计算结果表明,现有色差公式计算的图像明度差和彩度差与实际色差感觉有明显的系统性差异,图像内容对计算色差与色差感觉的关系有一定影响,说明需要对原始色差公式进行改进。提出了用实验数据拟合直线斜率比值优化色差公式的方法,得到CIELAB(1.50:1)、CIEDE2000(2.29:1)、CIE94(3.04:1)和CMC(3.38:1)计算的色差比原始公式有明显的改善,其中CIEDE2000(2.29:1)计算结果受图像内容的影响最小。用第二组实验数据检验色差公式的优化效果也证明,这种优化方法准确,简单,具有普遍适用性。

Study of Color Difference Evaluation in Color Digital Images

Two psychophysical experiments, experiment I and experiment II, were conducted to test color difference calculation method in images. Five ISO SCID images were used as test images and the test image pairs were displayed on EIZO CG 19 monitors. The computed color difference with CIELAB, CIEDE2000, CIE94 and CMC formulae showed that the calculated color difference in lightness and chroma attributes behaved very differently and the color image contents had some effects on the color sensation. An optimization method of color difference formulae is proposed based on the experiment I data. The optimized formulae CIELAB(1.501), CIEDE2000(2.291), CIE94(3.041) and CMC(3.381) perform much better than the original one and CIEDE2000(2.291) is the best among the four. The optimized formulae are also tested by the experiment II data, which proves that the optimized method proposed is accurate, simple and practical.