Steve on Image Processing

Concepts, algorithms & MATLAB

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Superpixel Posterization 6

Posted by Steve Eddins,

Today's blog post was inspired by an example written by my friend and Image Processing Toolbox developer, Alex Taylor. A few years back, Alex tinkered with using toolbox algorithms to achieve a pseudo-artistic "posterization" effect, like this: ... read more >>

What is the Shape of a Pixel? 6

Posted by Steve Eddins,

What is the shape of a pixel? At various times, I have a pixel as a square (often), a point (sometimes), or a rectangle (occasionally). I recall back in grad school doing some homework where we were treating pixels as hexagons.... read more >>

Minimum Feret Diameter 3

Posted by Steve Eddins,

Last time (if you can remember that long ago), I talked about how to find the maximum Feret diameter of a shape. The Feret diameter, sometimes called the caliper diameter, is illustrated by the diagram below. In a virtual sense, place the object to be measured inside the jaws of a caliper, with the caliper oriented at a specified angle. Close the jaws tightly on the object while maintaining that angle. The distance between the jaws is the Feret diameter at that angle.... read more >>

Feret Diameter: Introduction 8

Posted by Steve Eddins,

This is the first of a few blog posts about object measurements based on a concept called the Feret diameter, sometimes called the caliper diameter. The diagram below illustrates the concept. Place the object to be measured inside the jaws of a caliper, with the caliper oriented at a specified... read more >>

Frequency Samples for the Output of FFT2 1

Posted by Steve Eddins,

A MATLAB user recently contacted tech support with a question about the output of fft2. The user had a function, q(x,y), evaluated on an (x,y) grid. The grid evaluation produced a matrix that the user passed to fft2. The user's question: what are the spatial frequencies associated with the elements... read more >>