数字图像设备颜色特征化反向变换算法

CIEXYZ是一种不规则颜色空间，难以建立规则的三维查找表直接对数字图像设备进行反向变换.采用基于立方体细分的查找表插值匹配算法，通过设备RGB颜色空间中立方体的细分搜索和迭代，获得与目标颜色三刺激值匹配的设备RGB值.以打印机为例建立三维查找表，通过自制色卡验证了该算法和正向三维查找表算法有较高的重复性.并以ANSI IT8.7/2标准色卡的反向变换为例考察该算法的实际变换精度，结果表明，当CIE三刺激值XYZ位于打印机色域内时，该算法的平均/最大色差为2.06/6.31 CIELAB色差单位.此算法可以精确有效地实现数字图像设备的颜色特征化反向变换.

Inverse conversion algorithm of colorimetric characterization for digital imaging devices

The international commission on illumination XYZ(CIEXYZ) color space is an irregular space,so the regular three-dimension look-up table(3D-LUT) algorithm can not be directly applied for the inverse conversion of digital imaging devices.An algorithm using 3D-LUT with interpolation and matching based on cubic subdivision was presented to resolve this problem.In this algorithm,the cubic in the RGB color space was sub-divided to look up and approach the XYZ values of the target color so that the accurately matched device RGB data were found.As an example,the 3D-LUT of a printer was established.The repeat accuracy between the forward and inverse conversions was very high through the self-made color chart.To investigate the actual transformation accuracy of the inverse colorimetric characterization algorithm,the ANSI IT8.7/2 standard color chart was used as sample.The result showed that the average/maximum color difference reached 2.06/6.31 CIELAB units using this new algorithm when the CIEXYZ tristimulus values were in the printer gamut.Hereby the proposed algorithm is accurate and effective for the inverse conversion of the colorimetric characterization of digital imaging devices.