I-Jong Lin

On-Demand Digital Print Services: A New Commercial Print Paradigm as an IT Service Vertical

On-demand digital print service is a form of personalized manufacturing service. Key to commercial print value-creation chain is the service engagement and fulfillment between the content suppliers and the print service providers (PSP). Content suppliers are the service clients, they request print services and supply content for print. PSPs provide the fulfillment services to the content suppliers in exchange for payment: converting the supplied content into printed products and shipping them to the end-customer. In this paper, we will describe on-demand digital print service, and the application of service-oriented architecture (SOA) as platform to integrate information and communication technologies (ICT) into the end-to-end print service fulfillment process to enable digital print automation, and the SOA implementation assisted by process modeling. We also extend the SOA framework to include the order negotiation process and envisage a coupled demand-fulfillment paradigm. SOA-based digital print automation leverages from the integration of ICT into the print manufacturing operations management, it is an IT service vertical.

Operations simulation of on-demand digital print

On-demand digital print service is a form of personalized manufacturing service. Key to the commercial print value-creation chain is the responsive and accurate knowledge discovery and decision making throughout the service engagement and fulfillment between the content suppliers and the print service providers (PSP). The business model of on-demand print imposes a great challenge to the PSP factory design, production planning and management due to its intrinsic, highly volatile demand stream. It pushes the PSP resource planning and production management from a form of “tribal art” towards data driven management science. Operations simulation and its practice is an integral component of the data-driven decision making process, and is gaining growing significance. In this paper, we describe operations simulation of an end-to-end digital print process; we treat the management of print manufacturing as a heterogeneous, concurrent, integrated system, accounting for the performance, efficiency, stability, and sustainability as organic system attributes. We exhibit the comparison between the simulation results and the factory internal audit information and show good agreement.

Digital print workflow optimization under due-dates, opportunity cost and resource constraints

On-demand digital printing is an example of emerging personalized manufacturing services. It provides unique opportunities to automate the printing process, enhance productivity, and better utilize resources such as equipment, servers and IT infrastructure. In this work, we present a unified solution approach to solve an important optimization problem in digital printing, viz., simultaneous mapping of component tasks of a print job to time steps (scheduling), selection of resources for these tasks, and mapping of tasks to resources (binding). We model print jobs, the relationships between them, and dependencies between tasks within a job, in terms of sequencing graphs. This formal representation is then used for scheduling and resource binding. The optimization objective is to enable justin-time manufacturing, that is, to minimize both the slack time (the duration between the delivery deadline and the completion time of the order) and the opportunity cost for job orders. The proposed approach uses genetic algorithms (GA) to systematically search the space of feasible solutions. The fitness function of the GA is carefully crafted to match the optimization objective. An integer linear programming (ILP) model is described to evaluate the GA heuristic by deriving optimal solutions for small problem instances. The optimization technique is further evaluated using print orders from a commercial print service provider and compared to baseline methods commonly implemented in the industrial settings.

ICC profiles: are we better off without them?

Before ICC profiles, a device-independent document would encode all color in a device independent CIE space like CIELAB. When the document was to be printed, the press person would measure a target and create a color transformation from the CIE coordinates to device coordinates. For office and consumer color printers, the color transformation for a standard paper would be hardwired in the printer driver or the printer firmware. This procedure had two disadvantages: the color transformations required deep expertise to produce and were hard to manage (the latter making them hard to share), and the image data was transformed twice (from input device to colorimetric and then to output device coordinates) introducing discretization errors twice. The first problem was solved with the ICC profile standard, and the last problem was solved by storing the original device dependent coordinates in the document- together with an input ICC profile-so the color management system could first collapse the two profiles and then perform a single color transformation. Unfortunately, there is a wide variety in the quality of ICC profiles. Even worse, the real nightmare is that quite frequently the incorrect ICC profiles are embedded in documents or the color management systems apply the wrong profiles. For consumer and office printers, the solution is to forgo ICC profiles and reduce everything to the single sRGB color space, so only the printer profile is required. However, the sRGB quality is insufficient for print solution providers. How can a modern print workflow solve the ICC profile nightmare?

On the Connections between Types and Service Level Agreements and Implications for Digital Commercial Printing and Other Domains

Digital commercial print providers are increasingly seeing more and more low-value, very short-run orders as a result of personalization and customization of content. In addition, consolidation due to margin pressure and low turnaround times necessitates a quicker reaction to scenarios such as acquiring additional capacity in the peak season or off-loading capacity during the off-peak season. Traditional tools for negotiating and acquiring customer orders are increasingly becoming prohibitive in this environment due to their high costs and lack of ability to make rapid changes. Tools that use machine readable service level agreements (SLAs) promise easier management of customer orders, but are currently not widely used in manufacturing domains such as digital commercial printing. If SLAs are to appear in manufacturing and other related domains, they will need to deal with both SLA Monitoring and SLA Negotiations in the same framework. Programming languages have long used the concept of Types to guarantee behavior of programs. In this paper we show that there is a deep connection between Types and SLAs. The connection stems from the fact that both the Types as well as the SLAs are inherent guarantees about the run-time behavior. The mapping between Types and SLAs is shown by formulating problems in both the domains using notations which have similar semantics. In particular, we show: 1) SLA Monitoring has a parallel in Type Checking, 2) SLA Negotiation has a parallel in Type Inference, and 3) SLA Inhabitation has a parallel in Type Inhabitation. We also briefly mention how the rich meta-theorems about types such as preservation, progress and replacement theorems can be used to reason about SLAs, especially for services which deliver manufactured products.

Assessing color reproduction tolerances in commercial print workflow

Except for linear devices like CRTs, color transformations from colorimetric specifications to device coordinates are mostly obtained by measuring a set of samples, inverting the table, and looking up values in the table (including interpolation), and mapping the gamut from input to output device. The accuracy of a transformation is determined by reproducing a second set of samples and measuring the reproduction errors. Accuracy as the average predicted perceptual error is then used as a metric for quality. Accuracy and precision are important metrics in commercial print because a print service provider can charge a higher price for more accurate color, or can widen his tolerances when customers prefer cheap prints. The disadvantage of determining tolerances through averaging perceptual errors is that the colors in the sample sets are independent and this is not necessarily a good correlate of print quality as determined through psychophysics studies. Indeed, images consist of color palettes and the main quality factor is not color fidelity but color integrity. For example, if the divergence of the field of error vectors is zero, color constancy is likely to take over and humans will perceive the color reproduction as being of good quality, even if the average error is relatively large. However, if the errors are small but in random directions, the perceived image quality is poor because the relation among colors is altered. We propose a standard practice to determine tolerance based on the Farnsworth-Munsell 100-hue test (FM-100) for the second set and to evaluate the color transpositions-a metric for color integrity-instead of the color differences. The quality metric is then the FM-100 score. There are industry standards for the tolerances of color judges, and the same tolerances and classification can be use for print workflows or its components (e.g., presses, proofers, displays). We generalize this practice to arbitrary perceptually uniform scales tailored to specific applications and present an implementation. In essence, we propose to extend the color discrimination test procedures used to evaluate human observers, to mechanical and electronic color reproduction devices.

A GPU accelerated PDF transparency engine

As commercial printing presses become faster, cheaper and more efficient, so too must the Raster Image Processors (RIP) that prepare data for them to print. Digital press RIPs, however, have been challenged to on the one hand meet the ever increasing print performance of the latest digital presses, and on the other hand process increasingly complex documents with transparent layers and embedded ICC profiles. This paper explores the challenges encountered when implementing a GPU accelerated driver for the open source Ghostscript Adobe PostScript and PDF language interpreter targeted at accelerating PDF transparency for high speed commercial presses. It further describes our solution, including an image memory manager for tiling input and output images and documents, a PDF compatible multiple image layer blending engine, and a GPU accelerated ICC v4 compatible color transformation engine. The result, we believe, is the foundation for a scalable, efficient, distributed RIP system that can meet current and future RIP requirements for a wide range of commercial digital presses.