(2) How the display device profile works
1 The characteristics of the monochrome display device and the monochrome input device are very similar, and the PCS value corresponding to the device value is also obtained by reading the gray scale reproduction curve label.
2 The ICC color profile of the color display converted based on the matrix/gradation reproduction curve contains the tag information shown in Table 4.
The display ICC color profile implements bidirectional conversion from RGB to PCS. Because the display is both a source device (eg, from display to printer) and a destination device (eg, from scanner to display). The conversion process from RGB to PCS is similar to the conversion process of the input device described above. The reverse process from PCS to RGB is:
Device R value = redTRC-1 [value of linear R] î™…
Device G value = redTRC-1 [value of linear G] î™…
Device B value = redTRC-1 [value of linear B] î™…
Similarly, the matrix/gradation replication curve model curve can only be used for the ICC color profile of the color display when the connection space of the profile is CIEXYZ. If the profile connection space is CIELAB, multidimensional lookup table mode is used to perform the device value to the property. Conversion of file connection space. This has the same working principle as the above-mentioned multi-channel input device characteristic file based on the lookup table mode, which will not be described here.
(3) How does the output device profile work?
1 The monochrome output device profile is also converted between the device value and the corresponding PCS value by reading the grayscale copy curve label.
2 Color output device characteristics The article describes a two-way conversion process. The output device can be both a source device and a destination device. It uses multidimensional lookup table mode for conversion, including three conversion methods.
The label elements that the color output device profile must contain are shown in Table 5.
In the input device properties file, the conversion process using the AtoB0 tag has been described. Then the B2An tag is used to convert from the property file connection space to the device. The data and information are read in the same manner as the tag AtoB0 in the input device property file. Here, n is different for different color conversion methods. 0 represents equal ratio compression, 1 represents relative chroma matching, and 2 represents saturation priority. Different replication intents also correspond to different color lookup tables, so the output device must include six labels. When converting from the PCS space to the output device space, the color management module CMM calls the color profile and selects a copy intent such as relative chroma matching, then the CMM reads the color lookup table corresponding to B2A1 and calculates the relative color from the LAB value. The degree match is intended to duplicate the CMYK value for this color.
In short, the ICC color profile can be used to achieve color conversion in different color spaces based on the color measurement data, simplifying the worldwide problem of color reproduction and improving the quality of color reproduction. (Author: Yang Ping)