Algorithm of Double-Chroma Ink Mapping for Multi-Color Printer

Aiming at three color pairs of Lk &K, Lc & C, Lm &M, which are commonly used on multi-color inkjet printers. Based on colorimetric matching, polynomial fitting was used to establish a mapping relationship between each pairs of double chroma ink ,and fitting accuracy was contrasted between different fitting times. Experimental results show that the quartic polynomial can achieve better accuracy than the conic fitting. The study is great significance for printer’s color separation which has the two levels of color channel.

A novel camera calibration method for fish-eye lenses using line features

In this paper, a novel method for the fish-eye lens calibration is presented. The method required only a 2D calibration plane containing straight lines i.e., checker board pattern without a priori knowing the poses of camera with respect to the calibration plane. The image of a line obtained from fish-eye lenses is a conic section. The proposed calibration method uses raw edges, which are pixels of the image line segments, in stead of using curves obtained from fitting conic to image edges. Using raw edges is more flexible and reliable than using conic section because the result from conic fitting can be unstable. The camera model used in this work is radially symmetric model i.e., bivariate non-linear function. However, this approach can use other single view point camera models. The geometric constraint used for calibrating the camera is based on the coincidence between point and line on calibration plane. The performance of the proposed calibration algorithm was assessed using simulated and real data.

Least Squares Problems with Absolute Quadratic Constraints

This paper analyzes linear least squares problems with absolute quadratic constraints. We develop a generalized theory following Bookstein's conic-fitting and Fitzgibbon's direct ellipse-specific fitting. Under simple preconditions, it can be shown that a minimum always exists and can be determined by a generalized eigenvalue problem. This problem is numerically reduced to an eigenvalue problem by multiplications of Givens' rotations. Finally, four applications of this approach are presented.