30. August 2014       News, Computer Vision Digest

Third computer vision digest. Your monthly portion of news in computer vision for August 2014.

In this issue:

Previous issues:


 16. August 2014       OpenCV, Tutorials

Eigen is a C++ template library for matrix and vector operations. It is highly optimized for numeric operations and support vectorization and use aligned memory allocators.

When it comes to matrix operations, Eigen is much faster than OpenCV. However, it can be situations when it is necessary to pass Eigen data to OpenCV functions.

In this post I will show how to map Eigen data to OpenCV with easy and efficient way. No copy, minimal overhead and maximum syntax sugar:

Simple case

Eigen::ArrayXXd img(480, 640);
...
cv::imshow("test", eigen2cv(img));

Proposed approach does not limited to continuous memory layout - it support expression and blocks as well. If given expression has to be evaluated - it will be evaluated into temporary dense storage and then mapped to OpenCV structure:

Expressions

// Unsharp mask
Eigen::ArrayXXd img, blur;    
cv::GaussianBlur(eigen2cv(img), eigen2cv(blur));

cv::imshow("sharpened", eigen2cv(1.5 * img - 0.5 * blur));


 07. August 2014       News, Books, Tutorials, OpenCV

www.pyimagesearch.com

Let me introduce you Adrian Rosebrock and his http://www.pyimagesearch.com/ website. It’s about computer vision and image processing using Python and OpenCV. Looks like there are more than one person that like to share programming experience via blogging :)

Here’s how Adrian position himself:

This blog is dedicated to helping other programmers understand how image search engines work. While a lot of computer vision concepts are theoretical in nature, I’m a big fan of “learning by example”. My goal is to distill my life experiences in building image search engines into concise, easy to understand examples.

I hope you will enjoy reading Adrian’s posts on superpixels, histogram matching and color clustering. In addition, he wrote a book on using OpenCV in Python.

Practical Python and OpenCV eBook

Happy reading!


 14. July 2014       OpenCV, Algorithms, Reddit

This was a request from /r/computervision. A reddit member was asking on how to count number of eggs on quite noisy image like you may see below. I’ve decided to write a simple algorithm that does the job and explain how it works.

beforeafter


 05. July 2014       News, Computer Vision Digest

This is a second issue of monthly computer vision digest - a list things that you don’t wanna miss, a list of what happened in computer vision in June 2014.

Previous issues:

In this issue:


 20. May 2014       OpenCV, Cloud computing, Tutorials

In this post I’ll show you how you can train cascade classifier with OpenCV very quickly even if you have low-end hardware using virtual machine in the cloud.