Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Shape-from-Shading for Oblique Lighting with Accuracy Enhancement by Light Direction Optimization | Hindawi Publishing Corporation EURASIP Journal on Applied Signal Processing Volume 2006 Article ID 92456 Pages 1-10 DOI ASP 2006 92456 Shape-from-Shading for Oblique Lighting with Accuracy Enhancement by Light Direction Optimization Osamu Ikeda Faculty of Engineering Takushoku University 815-1 Tate-machi Hachioji Tokyo 193-0985 Japan Received 16 December 2004 Revised 12 February 2006 Accepted 18 February 2006 Recommended for Publication by Dimitrios Tzovaras We present a shape-from-shading approach for oblique lighting with accuracy enhancement by light direction optimization. Based on an application of the Jacobi iterative method to the consistency between the reflectance map and image four surface normal approximations are introduced and the resulting four iterative relations are combined as constraints to get an iterative relation. The matrix that converts the shading information to the depth is modified so as to be uniform over the whole image region making the iteration stable and as a result the resulting shape more accurate. Then to enhance the accuracy the light direction is optimized for slant angle using two criteria based on the initial boundary value and the rank of the converting matrix. The method is examined using synthetic and real images to show that it is superior to the current state-of-the-art methods and that it is effective for oblique light direction whose slant angle ranges from 55 to 75 degrees. Copyright 2006 Hindawi Publishing Corporation. All rights reserved. 1. INTRODUCTION Shape reconstruction from a single shading image has been studied for decades 1 producing a variety of approaches using minimization 2 3 linearization 4 propagation 5 6 deformable model 7 viscosity solutions 8-11 an attenuation term of the form 1 rr2 12 and the Helmholtz reciprocity 13 that also uses the attenuation term. They however still fail to produce acceptable shapes. One of the reasons may be that the iterative operations used in those methods .
