This chapter explores a class of image operations in which the content of the image is not "changed" as such, but its context—the array that contains it—is changed. In it, you will learn what the basic geometric image transforms are and see how they are implemented as computer algorithms. Geometric transforms include:
• translation, or shifting the image;
• rotation, or turning the image;
• scaling, or resizing the image;
• flipping and flopping, or mirroring the image;
• cropping and floating, or cutting off or adding to the image;
• resampling, or enlarging and shrinking the image.
The results of geometric transforms appear obvious—the image is shifted, turned, enlarged, or shrunk. Not so obvious is the manipulation of the discrete pixel structure that can result in the loss of image information. The better you understand why and how information is lost, the better you can manipulate and assemble images into track-and-stack images, movies, and great color pictures.
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