Sooner or later, when working with images, you will find you need to alter them: be it by applying artistic filters, extrapolating certain sections, blending two images, or whatever else your mind can conjure. This chapter presents some techniques that you can use to alter images. By the end of it, you should be able to perform tasks such as sharpening an image, marking the contours of subjects, and detecting crosswalks using a line segment detector. Specifically, our discussion and code samples will cover the following topics:
- Converting images between different color models
- Understanding the importance of frequencies and the Fourier transform in image processing
- Applying high-pass filters (HPFs), low-pass filters (LPFs), edge detection filters, and custom convolution filters
- Detecting and analyzing contours, lines, circles, and other geometric shapes
- Writing classes and functions that encapsulate the implementation of a filter
