Steve on Image Processing

Timing the FFT 1

Posted by Steve Eddins,

Timing the FFT I've seen two questions recently about the speed of the fft function in MATLAB. First, a tech support question was forwarded to development. The user wanted to know how to predict the computation time for an FFT of a given length, N. This user was interested in values of N... read more >>

Comparing the geometries of bwboundaries and poly2mask 1

Posted by Steve Eddins,

Comparing the geometries of bwboundaries and poly2mask  MATLAB user Meshooo asked a question on MATLAB Answers about a problem with the createMask function associated with impoly. Meshooo observed a discrepancy between the output of bwboundaries and the mask created by createMask.I want to describe the issue in more general terms here as a conflict between the geometry... read more >>

roifill design critique 6

Posted by Steve Eddins,

roifill design critique  "Is there anything else you would like to tell us?"This was the question whose answer led me to revisit an old friend of mine, the roifill function. This is a function that smoothly fills a specified region of interest in a gray-scale image. I implemented it in the early 1990s... read more >>

R2014a shipped! (And the developer says, “Wait, what?”) 8

Posted by Steve Eddins,

R2014a shipped! (And the developer says, “Wait, what?”) At MathWorks, the software developers' sense of calendar time is SO out of sync with the real world. In the real world, MathWorks shipped R2014a, the first of our two annual releases, last week. In the developers' world, R2014a is old news. Right now all the developers are heads-down and... read more >>

regionprops, tables, and struct2table 7

Posted by Steve Eddins,

regionprops, tables, and struct2table Today I was talking to Spandan (a regular guest blogger here) about the history of the Image Processing Toolbox function regionprops. This function is a widely-used work-horse of the toolbox. Many of my blog posts here have shown it in practice.The function regionprops computes properties of regions of pixels. Most... read more >>

Update to TopoToolbox

Posted by Steve Eddins,

Update to TopoToolbox  In 2007 I did a series of blog posts on developing MATLAB algorithms for a topological measurement called upslope area, a measurement related to digital elevation models (DEMs). The upslope area of a point (pixel) is the total area on the terrain above that point that drains through it. I... read more >>

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