A method to accurately align plane curves related by projective transform is described in this paper. Superior accuracy and efficiency are achieved by the use of super-curve and B-spline fusion. A super-curve is formed by superimposing two transform related and aligned curves upon each other. The B-spline fusion technique uses a single B-spline to approximate the super-curve and to align the two curves at the same time. The eight-parameter projective transform is decomposed into a simple two-parameter projective transform and an affine transform, for which a linear solution can be found. Therefore the search in the traditional eight dimensional space is reduced to a two dimensional search. The major contribution of the paper lies in the novel use of a single B-spline to represent two curves, whereas in previous approaches each curve is represented with a separate B-spline. This use of a single B-spline gives higher resolution from the two point sets instead of one. So the final result is more robustness to sampling noise. It also provides a simple and integrated framework in solving the curve matching and the transform recovery problems simultaneously.

We solve the 2-D affine image registration problem by curve matching and alignment. Our approach starts with a super-curve, which is formed by superimposing two affine related curves in one coordinate system. We use B-spline fusion technique to find a single B-spline approximation of the super-curve and a registration between the two curves simultaneously. This approach achieves superior accuracy and efficiency in curve matching and alignment. We then address the occlusion problem by finding partial match between the curves segmented using inflections and cusps, which are affine invariant. The combination of edge detection and curve alignment lead to accurate image registration.

An affine invariant 2D curve matching and alignment approach is proposed to solve the image registration problem. Superior accuracy and efficiency is achieved by a concept called super-resolution curve and a technique called B-spline fusion. A super-resolution curve is formed by superimposing two affine related and registered curves (in discrete form) upon each other. The B-spline fusion technique is designed to obtain a single B-spline approximation of the super-resolution curve and registration estimate simultaneously. Occlusion is handled by curve segmentation using inflections and cusps, which are affine invariant. Partial match then becomes possible by matching segments of curves. A complete image registration framework based on edge detection and curve alignment is then proposed. Accurate registration results have been achieved.

Compression on a watermarked image can significantly affect the detection of the embedded watermark. To show that a particular watermarking scheme is robust against compression, simulation is often relied upon. In this paper, we investigate this problem analytically. We first characterize the noise introduced by JPEG compression. We then propose a maximum a posteriori (MAP) detector, analyze its performance, and demonstrate that it has superior performance over the correlation detector.

This paper proposes methods for designing, tracking and coding hierarchical two-dimensional (2-D) content-based mesh representations. The design procedure consists of constructing a fine-to-coarse hierarchy of Delaunay meshes, using image- and shape-based criteria for mesh geometry simplification. Hierarchical tracking employs a coarse-to-fine strategy with mesh-based motion vector optimization. We introduce new techniques to maintain the initial mesh hierarchy and topology during tracking by imposing certain constraints at each stage of the procedure. The hierarchical compression technique is based on a nearest neighbor ordering of mesh node points. This ordering serves to identify the mesh boundary nodes as well as establish spatial predictors for differential coding of node coordinates and motion vectors. The proposed hierarchical mesh representation, which has applications in object-based video manipulation, investing, and compression, provides improved tracking performance (compared to a nonhierarchical representation) and allows progressive (scalable) transmission of the object geometry (including shape) and motion information, as well as variable level-of-detail rendering. Experimental results are presented to compare the tracking and compression performance of hierarchical versus nonhierarchical mesh representations and to demonstrate the tradeoff between image quality and mesh bit rate for 2-D mesh-based video object rendering.

Neugebauer modeling plays an important role in obtaining end-to-end device characterization profiles for halftone color printer calibration. This paper proposes total least square (TLS) regression methods to estimate the parameters of various Neugebauer models. Compared to the traditional least squares (LS) based methods, the TLS approach is physically more appropriate for the printer modeling problem because it accounts for errors in the measured reflectance of both the primaries and the modeled samples. A TLS method based on print measurements from single-colorant step-wedges is first developed. The method is then extended to incorporate multicolorant print measurements using an iterative algorithm. The LS and TLS techniques are compared through tests performed on two color printers, one employing conventional rotated halftone screens and the other using a dot-on-dot halftone screen configuration. Our experiments indicate that the TLS methods yield a consistent and significant improvement over the LS-based techniques for model parameter estimation. The gains from the TLS method are particularly significant when the number of patches for which measured data is available is limited.

The Neugebauer model is a powerful tool in obtaining end-to-end device characterization profiles for halftone color printer calibration. In this paper, we propose total least square (TLS) regression methods to estimate the parameters of Neugebauer models. Compared to the traditional least squares (LS) based methods, the TLS approach is a physically more appropriate procedure, because it accounts for errors in the measured reflectance of both the selected primaries and the modeled reflectance. The proposed TLS techniques are tested on a Xerox color printer with rotated halftone screen, and the results are compared with the LS based algorithms. Our experiments indicate that the TLS methods yield a significant improvement over the LS based techniques for model parameter estimation.