Geometric Transformations
This document provides a comprehensive overview of geometric transformations, including translation, rotation, scaling, and shear. It discusses similarity transformations, affine transformations, and projective transformations (homographies), detailing their degrees of freedom (DoF) and requirements, such as the number of corresponding points needed to solve them. The impact of aspect ratios, and how to compute these transformations using homogeneous coordinates, is also covered. By examining these concepts, readers will gain a clearer understanding of geometric transformations in planar contexts.
Geometric Transformations
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Presentation Transcript
Geometric Transformations CSE P 576 Larry Zitnick (larryz@microsoft.com)
Similarity transformations Similarity transform (4 DoF) = translation + rotation + scale
Affine transformations Affine transform (6 DoF) = translation + rotation + scale + aspect ratio + shear
What is missing? Canaletto Are there any other planar transformations?
General affine We already used these How do we compute projective transformations?
Homogeneous coordinates One extra step:
Projective transformations a.k.a. Homographies “keystone” distortions
Finding the transformation How can we find the transformation between these images?
Finding the transformation Translation = 2 degrees of freedom Similarity = 4 degrees of freedom Affine = 6 degrees of freedom Homography = 8 degrees of freedom How many corresponding points do we need to solve?