Nonlinear RGB-to-XYZ Mapping for Device Calibration

We introduce a new non-linear method for RGB-to-XYZ color calibration based on the technique of thin plate splines. Originally, thin plate splines were designed for deformable matching between 2-dimensional images for object recognition. We use 3-dimensional thin plate splines to map between sets of RGB device coordinates and corresponding sets of CIE XYZ coordinates. Tests calibrating several displays as well as a camera show thin plate spline calibration to be more accurate than existing linear or non-linear calibration methods

MULTI-LEVEL FAST MULTIPOLE METHOD FOR THIN PLATE SPLINE EVALUATION

Image registration is an important problem in image processing and computer vision. Much recent work in image registration is on matching non-rigid deformations. Thin Plate Splines are an effective image registration method when the deformation between two images can be modeled as the bending of a thin metal plate on point constraints such that the topology is preserved (non-rigid deformation). However, because evaluating the computed TPS model at all the image pixels is computationally expensive, we need to speed it up. We introduce the use of Multi-Level Fast Multipole Method (MLFMM) for this purpose. Our contribution lies in the presentation of a clear and concise MLFMM framework for TPS, which will be useful for future application developments. The achieved speedup using MLFMM is an improvement from O(N 2) to O(N log N). We show that the fast evaluation outperforms the brute force method while maintaining acceptable error bound. 1