Evaluation and use of gamut information in ICC output profiles

Abstract

A device’s color gamut is an important parameter in color managed workflows. With the increasing use of expanded gamut workflows and the need for more colorful products in large-format inkjet printing or packaging, the management and prediction of in-gamut colors is critical information for the content creator. When device color capability information is stored within the structure of an ICC profile, this information becomes readily available to any software utilizing the ICC profile in conjunction with an image or image data. A product may for example offer a gamut stain or warning to indicate to the user that the color under consideration is out of gamut of the destination print process. This research compares the gamut predictions of Adobe Photoshop, ArgyllCMS, BabelColor PatchTool, Esko Color Engine Pilot, Little CMS and MathWorks MATLAB. It is shown that the different tools may use different methods to determine the color gamut of a system. In general, the methods available include a Round Trip test, use of the ICC profile Gamut Tag and a Gamut Boundary Descriptor process. The Gamut Tag was read-in and displayed for different ICC profiles and differences in the tag contents was demonstrated. In total, 1729 CIELAB values, representing the PANTONE+ Solid Coated Library V2 were used and the percentage of in-gamut values using each software product was computed for different output print processes. There was a large difference in the predictions between the different products tested; the software tools variously predicted that 30–65 % of the library was in-gamut. A general philosophy of an ICC workflow is predictable result; while the ICC architecture is not intended to change a device’s gamut capabilities, it should be able to communicate accurate and consistent gamut information. As more and more software systems are starting to present gamut data, it is important that systems do not predict disparate results.