Data Conversion

Steve Eddins manages the Image & Geospatial development team at The MathWorks and coauthored Digital Image Processing Using MATLAB. He writes here about image processing concepts, algorithm implementations, and MATLAB.

In this part of the connected component labeling series, I'll finally get to one of the algorithms actually used in the Image Processing Toolbox. It's based on a technique called union-find, as described in Sedgewick's Algorithms in [...]

Early in my graduate school days, I once spent a couple of days poring over code listings trying to find the cause of a mysterious bug. Eventually I discovered that the code had a "1" somewhere it should have had an "l". (Or maybe it was the other way around.) With the low-resolution displays [...]

In Part 2 of the upslope area series, I showed an M-file, pixelFlow, that could calculate a pixel's flow direction and magnitude according to the D-infinity method of Tarboton. Let's try the function with a simple test case first, and then we'll try it with some DEM [...]

OK, I've learned an important lesson about this blog: I really shouldn't start up two topics series at the same time. It's too hard to find the time to compose posts on both topics each week, and so the frequency of my posts drops off. [...]

A few weeks ago I promised a series on developing a MATLAB algorithm to compute upslope area. Now I'm ready to begin that project in earnest. First, though, I'd like to comment on the motivation for this series. Specifically, why look at a method from the area [...]

In the previous post in this series I talked about forming a graph based on pixel neighbor relationships, and then finding the connected components of the graph. Another approach starts by finding a foreground pixel and then iteratively searching that pixel's neighbors to find the connected [...]

A new release (R2007a) of the Student Version of MATLAB & Simulink is now available. Several add-on products are now bundled with the Student Version, including the Image Processing Toolbox. See the Student Version product page for details.

[Here's a quick note for you, composed and delivered from the lovely confines of Boston's Logan International Airport. Don't worry, I'll get back to my connected components and upslope area topics real soon now.] Adobe recently announced the new release of Photoshop, called Photoshop CS3. At the same time, they announced an additional Photoshop product, called [...]

A long time ago, blog reader Brendon asked me if I knew of a way to compute something called upslope area in MATLAB. I responded that I had never heard of that before. Brendan explained that it was a measurement related to digital elevation models (DEMs). The upslope area of a point [...]

In response to my last post about connected component labeling algorithms, blog reader JanKees wanted to know how to find neighboring pixel pairs programmatically. Prompted by this question, I thought I would describe a MATLAB indexing technique that is useful for various kinds of neighbor searching [...]