It has been years since I last used OpenCV. We (me and friends working on a lab at the university) used it to process images on batches or to process frames live from a webcam. Things could have been much easier if I knew GStreamer back then. Said so, I decided to take a look at gst-opencv to see what we already can do with it.
There are a few features wrapped as elements at this moment and they work quite well, but it could have a much larger feature set and it seems no one has been recently working on this. Given those and having a little spare time these days, I decided to start hacking on gst-opencv and trying to put it together with the other modules. I'd prefer to have a gst-opencv module, but adding it as a new plugin into gst-plugins-bad is also an option. What do you think?
[Edited: It seems the videos can only be seen directly on the post at blogspot]
Some nice stuff can already be done with the current elements. Let me show some.
I recorded this video outside some minutes ago:
We can use edgedetect on it and see its edges:
Command: gst-launch uridecodebin uri=youruri ! queue ! ffmpegcolorspace ! edgedetect ! ffmpegcolorspace ! theoraenc ! oggmux ! filesink location=result.ogg
Or we can segment it with pyramidsegment and have a nice effect (some people would enjoy this in PiTiVi?) or use it in machine vision stuff?
Command: gst-launch uridecodebin uri=youruri ! queue ! ffmpegcolorspace ! pyramidsegment ! ffmpegcolorspace ! theoraenc ! oggmux ! filesink location=result.ogg
OpenCV already ships some face detection profiles for you (at Ubuntu, it goes into /usr/share/opencv/haarcascades/), so you can use them with facedetect element, or train your own classifiers to use with it. I stood with the default and tried on some pictures, here are 2 of them:
I think it works pretty well :)
You can disable the circles and just get messages with the faces' positions and do whatever you want with them.
Other than those, there's also 'textwrite', 'templatematch' and 'faceblur' elements.
I've been working on a simple base class that will make it easier to map simple 1 to 1 OpenCV functions into elements and providing some common properties (like ROI and COI) and GstBuffer-IplImage conversion. This will help covering more functions and should be enough to get me acquainted again to the API, after it I can go for the fancier stuff.
For example, take cvSmooth function, we should only have to write code to map its parameters into properties and a simplified chain function that already works on IplImages instead of GstBuffers.