Steve on Image Processing

Concepts, algorithms & MATLAB

Logical indexing 3

Posted by Steve Eddins,

One of my favorite aspects of MATLAB for image processing is how I can use a binary image to index directly into a grayscale image. The technique is called logical indexing, and I'm going to show you how it works today.... read more >>

Gaussian filtering with imgaussfilt 2

Posted by Steve Eddins,

With the R2015a release a couple of years ago, the Image Processing Toolbox added the function imgaussfilt. This function performs 2-D Gaussian filtering on images. It features a heuristic that automatically switches between a spatial-domain implementation and a frequency-domain implementation.... read more >>

Aliasing and image resizing – part 3 4

Posted by Steve Eddins,

Today I'll try to wrap up my discussion about how aliasing affects image resizing and about how the imresize function tries to prevent it. (This is called antialiasing.) Let me show you where we are going. Here is the zone plate image I showed last time.... read more >>

Aliasing and image resizing – part 2 7

Posted by Steve Eddins,

In my 03-Jan-2017 post, I introduced my new topic: aliasing, especially as it relates to resizing images. Today I will get more specific about what aliasing actually is.... read more >>

MATLAB arithmetic expands in R2016b

Posted by Steve Eddins,

Earlier this summer, I was writing some color-space conversion code. At one point in the code, I had a Px3 matrix called RGB, which contained P colors, one per row. I also had a 1x3 vector, v. I needed to multiply each column of RGB by the corresponding element of... read more >>

Filling holes in outline text 7

Posted by Steve Eddins,

Intrepid MathWorks application engineer Brett Shoelson recently got a user question that caught my attention. Consider an image containing text characters in outline form, such as this:... read more >>

Getting the math right 9

Posted by Steve Eddins,

Because I work regularly with developers on the MATLAB Math team, I see the questions that come to them from tech support. Today there was an interesting one.... read more >>

These postings are the author's and don't necessarily represent the opinions of MathWorks.