Image Processing with ImageJ by 2013

Author:2013
Language: eng
Format: epub
Publisher: Packt Publishing

Tip

All the different spatial filters that we have presented (smoothing, median, edge detection, and so on) can be applied only to a certain region of the image. Draw a selection before running the filtering process, and the only pixels affected will be those inside the selection.

The Fourier transform

The Fourier transform, named after Jean Baptiste Joseph Fourier (1768-1830), is a mathematical operation that gives us another way to represent our image. Instead of using the spatial coordinates as arguments in our image, in the Fourier space, the argument is frequency. Every position corresponds to the weight that a certain frequency has in our image. The algorithm that ImageJ (and many other programs) uses to convert our image to the frequency space is called FFT (Fast Fourier Transform).

You are probably wondering what the entire previous paragraph meant. As we have done several times before, let's explain it with an example. Open the sin_pattern_1.tif and sin_pattern_2.tif images:

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