ITU-T T.42

This Recommendation defines a colour data representation method in order to make it possible to interchange continuous-tone colour image data over facsimile communication services such as Group 4 and Group 3 facsimile. CIELAB space is selected as the basic colour space mainly for hard copy (printed) application. CIE Illuminant D50 and its perfectly diffuse reflecting white point (X0 = 96.422; Y0 = 100.000; Z0 = 82.521) is selected as the basic illuminant and white point respectively. The default gamut range chosen is L*= [0, 100], a*= [-85, 85], b*= [-75, 125]. The exact expression is in terms of offset and range. The YCC space based on sYCC is selected also as the basic color space mainly for soft copy (displayed) application. CIE illuminant D65 and its perfectly diffuse reflecting white point (X0 = 95.045; Y0 = 100.000; Z0 = 108.892) is the illuminant and white point respectively. The default gamut is chosen is Y = [0, 1], Cb = [-0.5, 0.5], Cr = [-0.5, 0.5]. The exact expression is in terms of offset and range. The main difference from the previous version is the following: - ITU-YCC addition.