Dr. Matthew D. Gaubatz Profile

Dr. Matthew D. Gaubatz

at Hewlett-Packard Heartstream

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Publications (4)

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PROCEEDINGS ARTICLE | March 22, 2013

Stegatone performance characterization

Proc. SPIE. 8665, Media Watermarking, Security, and Forensics 2013

KEYWORDS: Visualization, Calibration, Image segmentation, Scanners, Digital watermarking, Computer programming, Printing, Halftones, Performance modeling

Read Abstract

Embedding data in hard copy is in widespread use for applications that include pointing the reader to on-line content by means of a URL, tracing the source of a document, labeling, and packaging. Most solutions involve placing overt marks on the page. The most common are 1D, 2D, and 3D (color) barcodes. However, while barcodes are a popular means for encoding information for printed matter, they add unsightly overt content. In order to avoid such overt content, Stegatones are clustered-dot halftones that encode a data payload by single-pixel shifts of selected dot-clusters. In a Stegatone, we can embed information in images or graphics – not in the image file, as is done in traditional watermarking, but in the halftone on the printed page. However, the recovery performance of stegatones is not well understood across a wide variety of printing technologies, models, and resolutions, along with variations of scanning resolution. It would thus be very useful to have a tool to quantify stegatone performance under these variables. The results would then be used to better calibrate the encoding system. We develop and conduct a test procedure to characterize Stegatone performance. The experimental results characterize Stegatone performance for a number of printers, scanners, and resolutions.

PROCEEDINGS ARTICLE | January 28, 2010

Pointing into remote 3D environments

Proc. SPIE. 7542, Multimedia on Mobile Devices 2010

KEYWORDS: Detection and tracking algorithms, Imaging systems, Cameras, Calibration, Video, Projection systems, Light sources and illumination, Prototyping, Content addressable memory, 3D image processing

Read Abstract

In anticipation of the proliferation of micro-projectors on our handheld imaging devices, we designed and tested a camera-projector system that allows a distant user to point into a remote 3D environment with a projector. The solution involves a means for locating a projected dot, and for adjusting its location to correspond to a position indicted a remote user viewing the scene through a camera. It was designed to operate efficiently, even in the presence of camera noise. While many camera-projector display systems require a calibration phase, the presented approach allows calibration-free operation. The tracking algorithm is implemented with a modified 2D gradient decent method that performs even in the presence of spatial discontinuities. Our prototype was constructed using a standard web-camera and network to perform real-time tracking, navigating the projected dot across irregularly shaped and colored surfaces accurately. Our tests included a camera-projector system and client on either side of the Atlantic Ocean with no loss of responsiveness.

PROCEEDINGS ARTICLE | February 12, 2007

The role of spatially adaptive versus non-spatially adaptive distortion in supra-threshold compression

Proc. SPIE. 6492, Human Vision and Electronic Imaging XII

KEYWORDS: Image compression, Visualization, Wavelets, Composites, Distortion, Image quality, Quantization, Image classification, Computer engineering, Electronic imaging

Read Abstract

In wavelet-based image coding, a variety of masking properties have been exploited that result in spatially-adaptive quantization schemes. It has been shown that carefully selecting uniform quantization step-sizes across entire wavelet subbands or subband codeblocks results in considerable gains in efficiency with respect to visual quality. These gains have been achieved through analysis of wavelet distortion additivity in the presence of a background image; in effect, how wavelet distortions from different bands mask each other while being masked by the image itself at and above threshold. More recent studies have illustrated how the contrast and structural class of natural image data influences masking properties at threshold. Though these results have been extended in a number of methods to achieve supra-threshold compression schemes, the relationship between inter-band and intra-band masking at supra-threshold rates is not well understood. This work aims to quantify the importance of spatially-adaptive distortion as a function of compressed target rate. Two experiments are performed that require the subject to specify the optimal balance between spatially-adaptive and non-spatiallyadaptive distortion. Analyses of the resulting data indicate that on average, the balance between spatially-adaptive and non-spatially-adaptive distortion is equally important across all tested rates. Furthermore, though it is known that meansquared- error alone is not a good indicator of image quality, it can be used to predict the outcome of this experiment with reasonable accuracy. This result has convenient implications for image coding that are also discussed.

PROCEEDINGS ARTICLE | March 18, 2005

Spatial quantization via local texture masking

Proc. SPIE. 5666, Human Vision and Electronic Imaging X

KEYWORDS: Image compression, Detection and tracking algorithms, Visualization, Wavelets, Computer programming, Discrete wavelet transforms, Image quality, Quantization, Bridges, Visual compression

Read Abstract

Wavelet-based transform coding is well known for its utility in perceptual image compression. Psychovisual modeling has lead to a variety of perceptual quantization schemes, for efficient at-threshold compression. Successfully extending these models to supra-threshold compression, however, is a more difficult task. This work attempts to bridge the gap between at threshold modeling and supra-threshold compression by combining a spatially-selective quantization scheme, designed for at-threshold compression with simple MSE-based rate-distortion optimization. A psychovisual experiment is performed to determine how textured image regions can be used to mask quantization induced distortions. Texture masking results from this experiment are used to derive a spatial quantization scheme, which hides distortion in high-contrast image regions. Unlike many spatial quantizers, this technique requires explicit side information to convey contrast thresholds to generate step-sizes. A simple coder is presented that is designed that applies spatially-selective quantization to meet any rate constraints near and above threshold. This coder leverages this side information to reduce the rate required to code the quantized data. Compression examples are compared with JPEG-2000 examples with visual frequency weighting. When matched for rate, the spatially quantized images are highly competitive with and in some cases superior to the JPEG-2000 results in terms of visual quality.

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