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abstract: 'Color separations (most often cyan, magenta, yellow, and black) are commonly used in printing to reproduce multi-color images. For mechanical reasons, these color separations are generally not perfectly aligned with respect to each other when they are rendered by their respective imaging stations. This phenomenon, called color plane [*misregistration*]{}, causes gap and halo artifacts in the printed image. Color trapping is an image processing technique that aims to reduce these artifacts by modifying the susceptible edge boundaries to create small, unnoticeable overlaps between the color planes (either at the page description language level or the rasterized image level). In this paper, we propose three low-complexity algorithms for automatic color trapping at the rasterized image level which hide the effects of small color plane mis-registrations. Our proposed algorithms are designed for software or embedded firmware implementation. The trapping method they follow is based on a hardware-friendly technique proposed by J. Trask (JTHBCT03) which is too computationally expensive for software or firmware implementation. The first two algorithms are based on the use of look-up tables (LUTs). The first LUT-based algorithm corrects all registration errors of one pixel in extent and reduces several cases of misregistration errors of two pixels in extent using only $727$ Kbytes of storage space. This algorithm is particularly attractive for implementation in the embedded firmware of low-cost formatter-based printers. The second LUT-based algorithm corrects all types of misregistration errors of up to two pixels in extent using $3.7$ Mbytes of storage space. This algorithm is more suitable for software implementation on host-based printers. The third algorithm is a hybrid one that combines look-up tables and feature extraction to minimize the storage requirements ($724$ Kbytes) while still correcting all misregistration errors of up to two pixels in extent. This algorithm is suitable for both embedded firmware implementation on low-cost formatter-based printers and software implementation on host-based printers. All three of our proposed algorithms run, in average, more than three times faster than a software implementation of JTHBCT03.'
author:
- 'Haiyin Wang,  Mireille Boutin,  Jeffrey Trask, and Jan Allebach, [^1][^2][^3]'
bibliography:
- 'IEEEabrv.bib'
- 'ColorTrappingRef.bib'
title: 'Three Efficient, Low-Complexity Algorithms for Automatic Color Trapping[^4]'
---

Color trapping, color plane misregistration, look-up tables.

[^1]: H. Wang, M. Boutin, and J. Allebach are with the School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907 USA e-mail: hw, mboutin, allebach @purdue.edu.

[^2]: J. Trask is with the Hewlett-Packard Company, 11311 Chinden Blvd. Boise, ID 83714.

[^3]: This research was described in part in H. Wang, M. Boutin, J. Trask and J. Allebach, “An efficient method for color trapping", in [*Color Imaging XIII: Processing, Hardcopy, and Applications, IS&T/SPIE Electronic Imaging Symposium*]{}, San Jose, CA, Jan-Feb 2008.

[^4]: This research was supported by the Hewlett-Packard Company.
