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.

When I started this blog in early 2006, one of my first series of articles was called "All About Pixel Colors." These articles discussed how MATLAB associates matrix values with specific screen pixel colors. The series talked about the two fundamental image display models (indexed and truecolor); the scaled indexed image variation; using indexed [...]

I'd like to welcome back guest blogger Stan Reeves, professor of Electrical and Computer Engineering at Auburn University. Stan will be writing a few blogs here about image deblurring. In [...]

In September I wrote about customer-reported speed issues related to TIFF files containing a very large number (thousands or tens of thousands) of images. I've started to call these things MMTs (massively multipage TIFFs). If you have experienced this kind of performance problem and you have an MMT that you'd be willing to share with [...]

Didja know about the Image Processing Toolbox function bwselect? For a blog post I wrote earlier this month, I wanted a binary image containing only the central blob indicated in red below:url = 'http://blogs.mathworks.com/images/steve/163/plateaus.png'; bw = imread(url); imshow(bw) annotation(gcf,'ellipse','LineWidth',3,... 'Position',[0.4931 0.463 0.07575 0.2029],... 'Color',[0.8471 [...]

Back in March I started writing about an algorithm implementation experiment for computing upslope area. Given an "image" whose pixel values are terrain elevations, the upslope area of a pixel is the area of the uphill terrain that drains through that pixel. I chose a paper that looked promising, and I wrote about my progress [...]

In a blog comment earlier this summer, someone asked how to find "which labeled regions have a bright spot greater than some threshold?" That's a good question. It can be done efficiently and compactly using the Image Processing Toolbox, but the techniques [...]

Since I originally posted my upslope toolbox to MATLAB Central back in August, I have heard from some experts about an issue related to NaNs in the DEM data. Specifically, some data sets record elevation only for DEM pixels within a particular catchment basin. Pixels [...]

We recently changed the view when you click on a category in the sidebar on the right. I haven't used categories much, but the other bloggers (Loren on the Art of MATLAB, Doug's Pick of the Week, and Inside the MATLAB Desktop) have been. The new view presents a much more concise summary of all the [...]

At the beginning of the upslope area series, I posted code showing how to compute the direction of maximum slope for a triangular facet, and how to compute the flow direction for a pixel. This purely scalar code ran fine, but more slowly than I wanted, so I decided to vectorize it before submitting [...]

In photography and color science, MathWorks developer Jeff Mather's personal interests intersect with his work. He guest-blogged here last year with a post about the CIE Standard Observer. Earlier this month, he posted on his personal blog about high dynamic range (HDR) imaging and associated tone mapping algorithms. If you want to know more about [...]