My computer:
Windows 10, Python 3.4, OpenCV 3.0.0

I had uncountable desperate attempts to install OpenCV 3.0 in my machine, including the always last plan when installing software: building it from the source. There is an apparently nice tutorial from the official OpenCV webpage which didn’t work for me because I needed to do a couple of steps, so please, try to follow this tutorial (section Building OpenCV from source) with this addition tips:

  • 7.2: Use the path you want, but remember that you will not be able to delete it (because you need to refer to that path) so choose wisely.
  • 7.4: You can use any Visual Studio. In fact, I used Visual Studio 13. Just remember to specify it when configuring CMake
  • 8,9,10,11: When you are checking and unchecking all those checkboxes you will realize that many of the options are not listed on the provided pictures. What to do in that case? Easy: just leave it there as it is.
  • 16: Some of the projects will not be built and will be skipped. Don’t worry.

Now, it’s supposed to be installed in your computer, and if you try to import cv2, it should work.
However, at least for me, it didn’t work. The final step to get rid of that annoying message is to add the appropiate path to the PATH system variable. This is the path that you have to add: X\bin\Release where X is the folder where you compiled it.

I hope this is helpful. This could have saved me many hours…