《数字图像处理 Digital Image Processing》课件 Image Restoration[精品].pptVIP

Geometric transformations Definition: geometric transformations modify the spatial relationships between pixels in an image. It is also called rubber-sheet transformations. In terms of digital image processing, a geometric transformation consists of two basic operations: 1) a spatial transformation, which defines the “rearrangement” of pixels on the image plane; 2) interpolation of gray-level, which deals with the assignment of gray-levels to pixels in the spatially transformed image. Lecture 14: Chapter 5 Image Restoration Mystery to be solved The right side is a famous picture called ‘The ambassadors’ painted by Hans Holbein in the year1533. What is the odd shaped object at the bottom of the painting? Solve the mystery using geometric transformation. Lecture 14: Chapter 5 Image Restoration Demonstration of uncovering the mystery using geometric transformation First, we are going to reveal the mystery, then followed by the explanation on how to do it. Matlab demo: anamorphosis.m Lecture 14: Chapter 5 Image Restoration Magnify digital images We already discussed image contraction by simply deleting some rows and columns in chapter 2. Now we discuss a more complex operation—magnification. Magnification requires two steps: 1) the creation of new pixel locations; 2) the assignment of gray levels to those new locations. Pixel replication is the simplest way of magnification, it is applicable when we want to increase the size of an image an integer number of times. Lecture 14: Chapter 5 Image Restoration Pixel replication example Task#1: Double the size of an image. We perform the task in following steps: Duplicate each column, this doubles the image size in the horizontal direction. Duplicate each row of the enlarged image to double the size in vertical direction. The same procedure is used to enlarge the image by any integer number of times (triple, quadruple, and so on). Lecture 14: Chapter 5 Image Restoration Matlab demonstration of pixel replication a=magic(3) b=