DevCon '05 abstracts
A1: What do image pixel values represent?Ann McCarthy, Lexmark International, Inc.
Image interpretation can affect the selection and control of color processing and can make or break the quality of the results. In addition, the three different classes of color rendering systems deal with image interpretation in different ways. This tutorial will provide background on essential color management concepts.
A2: What does ICC color rendering do to color?
Emmi Enoksson, Dalarna University, Sweden
Before we dive into programming details, this tutorial will provide a visual overview of rendering intents, the relationships between color space encodings and display devices, and important print colorant control concepts such as GCR.
A3: How SHOULD applications present color controls?
Chris Murphy, Color Remedies
This tutorial will discuss color management user interface design from an expert end user perspective. Users almost universally say that color management is too complicated and needs to be simplified.
This session will discuss exactly what users really mean when they say this: controls are not intuitive, forcing users to work and think in ways they don't naturally work or think, some controls are too simplistic while others are superfluous, and lead to application interoperability problems (for example, the discrepancy between conversions in desktop publishing applications and RIPs). Further, we'll discuss things users need, but don't know they need, including image and document metadata.
A4: When and how should a print job be encoded for print?
Phil Green, London College of Communication; Bob Hallam, Quebecor World
Commercial and publications print industries in Europe, US, and world wide are establishing standard practices to improve the color fidelity of digital print jobs. RGB workflows (with late-stage rendering to print encodings) will be compared to traditional workflows (with print-ready encodings set in design). The focus of the comparison will be on the impacts in color management controls and behaviors ? and factors that contribute to the predictability of the print outcome.
Along with this we will look at the impact of the transition in the print industry from ?local printing on traditional litho presses? ? with similar colorants across presses ? to an ?internationally distributed printing environment? that includes digital printing systems with dissimilar colorants? For example, similarity in colorants can no longer be assumed as the basis for color management in printing. As a result, ICC devicelink profiles become critical to the open exchange of print-ready files. Devicelinks can be used to maintain colorant allocations while adjusting tone -- or can twist primaries as needed ? but application support for devicelink profiles is currently limited.
The discussion will include a look at how color management responsibilities can be distributed ? between profiles, applications, and operating systems, and how color management function allocation impacts distributed color consistency.
A5: How should device drivers use ICC profiles?
Luke Wallis, Apple Computer, Inc
In a late-binding color workflow, color values are converted to the values needed by each particular display device just as the data is being processed for display. This tutorial will discuss how to construct device driver interactions with ICC profiles and with operating system color APIs. The particulars of exemplary print path software architectures will be explored.
Expert User Panel: "From the trenches"
Bob Hallam, Quebecor World; Don Hutcheson, Hutcheson Consulting ; Chris Murphy, Color Remedies ; Matt Phillips, Adobe Systems Inc.; Eric Magnusson, Left Dakota
Color managed use case examples from creative and prepress workflows. Recommendations on future directions for the ICC.
P1: Under the hood: the V4 CMM, V4 ICC profiles, and the new ICC Perceptual PCS
Max Derhak, Onyx Graphics Corp.
ICC profiles carry information that enables software, the software typically referred to as a color management module (CMM), to interpret color encodings from one device or imaging condition to another. The ICC specification itself pertains to the semantics and formatting of the information in ICC profiles. How is the information in ICC profiles intended to be used?
This tutorial will introduce the fundamentals of the V4 CMM color rendering architecture, and provide insight into particular color rendering aspects that may be handled in a CMM, including white point compensation, black point compensation, gamut mapping, and rendering differences as a function of source profile rendering or re-rendering into ICC PCS (ICC profile connection space). The ICC SampleICC code base will be used as an example. The discussion will include exploration of image adaptive methods enabled by the V4 architecture.
P2: ICC V4 colorimetric rendering intents
Marti Maria Saguer, Hewlett Packard
The ICC V4 media-relative colorimetric rendering (MRC) intent is strictly defined with a measurement basis. This supports the ICC V4 objective to enable dynamic (runtime adaptive) color rendering in ?smart? CMMs. This tutorial will examine ICC media relative colorimetric intent construction and the CMM rendering approaches that it supports. Differences between MRC in V2 and V4 will be evaluated.
The discussion will explore: the computation required to obtain the ICC absolute colorimetric rendering intent transform from MRC, handling illuminants that differ from D50, using the chromatic adaptation tag and the media white point tag, mixing MRC and perceptual PCS, the relationship between the perceptual rendering intent and the media-relative colorimetric rendering intent transforms within a single profile, and an introduction to Black Point Compensation (BPC).
P3: ICC V4 perceptual rendering intent
Jack Holm, Ingeborg Tastl, Hewlett Packard
The V4 perceptual rendering intent is quite different from that of V2. This tutorial will discuss the details of the enhancement ? as it affects particular classes of color rendering and as it impacts construction of the perceptual rendering intent tag data in a V4 profile. For example, the perceptual rendering transform in an input profile should (in some cases) be distinctly different from that in an output profile.
The discussion will include an analysis of ?media-relative colorimetric (MRC) rendering plus black point compensation (BPC)? as a first level perceptual rendering intent (i.e., How does BPC relate to perceptual black?), rendering transform invertability, and the new Perceptual Reference Medium Gamut (PRMG). Color appearance, viewing environment, and the relevance of the chromatic adaptation tag to the perceptual rendering intent transform will be discussed.
P4: Profile Identification and output condition metadata
Uwe-Jens Krabbenhoeft, Heidelbergerer Druckmaschinen AG
In color managed workflow scenarios, particularly in automated systems, it can be challenging to automate and simplify the selection of a correct profile for each particular printing process condition. Similarly, it can be challenging to determine whether an output profile linked with a received job file does correctly correspond to the required print process condition. This has been identified by graphic arts industry users as a high priority problem in ICC-based workflow systems.
The ICC proposes a specification change in collaboration with related standards groups that will provide a new set of tags to be used to identify the differentiating aspects of various printing systems. When these tags are populated by profile building software applications, and interrogated by print workflow systems and CMMs, the linkage between any particular print process condition ? and a correctly corresponding profile ? will be amenable to automation. The new ICC profile tags are also specified to correspond with JDF (Job Definition Format) profile identification information. The discussion will include explanation of the differentiating aspects, affecting color rendition, in printing systems.
P5: V4 LUT structures
Luke Wallis, Apple Computer, Inc.
V2 to V4 look-up table (LUT) structures and computational differences will be explained, with a look at how the V4 changes provide greater adaptability to device characteristics.
The discussion will include examination of computational procedures for populating V4 profile LUTs and matrices ? pertinent to profile building. Given that understanding, the computational steps required when using the profile LUTs and matrices in ICC V4 CMMs will be explored.
P6: Profile and CMM computational quality
Chris Cox, Adobe Systems Inc.
'Perfect math' doesn't always yield good results when building profiles. 8 bits is not enough for color rendering in many imaging applications. The source color space encoding, the destination color space encoding, the target customer for the system, the size of the LUTs in the profiles, and the LUT interpolation method used in the CMM all contribute to the quality of results.
This tutorial discussion will explore these interactions, and will include recommendations for testing CMM and profile accuracy, and recommendations pertinent to testing and improving CMM software performance.
