3d code graphics gui opencv programming qt vision

Moving to Qt on the SfM-Toy-Library project

Qt GUI for SfMToyLibFor those of you still interested, I’ve made the move to using Qt and QGLViewer in the SfM-Toy-Lib project. Getting rid of PCL dependency (I think it’s a bloated library), and burying FLTK long in the past, I feel much better about it now.
Get it on github:

graphics Java programming tips video

The woes of Frame Animation on Android [w/ code]

My adventures of getting frame animation on the Android 2.1 continue, and take a turn for the worse. Will I come up victorious in the end? Not sure…

ffmpeg graphics gui linux programming qt video

Showing video with Qt toolbox and ffmpeg libraries

I recently had to build a demo client that shows short video messages for Ubuntu environment.
After checking out GTK+ I decided to go with the more natively OOP Qt toolbox (GTKmm didn’t look right to me), and I think i made the right choice.
So anyway, I have my video files encoded in some unknown format and I need my program to show them in a some widget. I went around looking for an exiting example, but i couldn’t find anything concrete, except for a good tip here that led me here for an example of using ffmpeg’s libavformat and libavcodec, but no end-to-end example including the Qt code.
The ffmpeg example was simple enough to just copy-paste into my project, but the whole painting over the widget’s canvas was not covered. Turns out painting video is not as simple as overriding paintEvent()…
Firstly, you need a separate thread for grabbing frames from the video file, because you won’t let the GUI event thread do that.
That makes sense, but when the frame-grabbing thread (I called VideoThread) actually grabbed a frame and inserted it somewhere in the memory, I needed to tell the GUI thread to take that buffered pixels and paint them over the widget’s canvas.
This is the moment where I praise Qt’s excellent Signals/Slots mechanism. So I’ll have my VideoThread emit a signal notifying some external entity that a new frame is in the buffer.
Here’s a little code:


The strange case of the BackgroundWorker and the disappearing exception

I was recently building a simple GUI in .NET to operate an algorithm as part of a school project, and I encountered a weird problem using BackgroundWorkers. I spent a lot of time debugging it, mainly because the code seemed to be perfect (which was true) but the run-time behavior was so strange…
Anyway, to make my algorithm as weakly-coupled as possible decided not to use BackgroundWorker.ReportProgress‘, because then my algorithm will have to know what a BackgroundWorker is…
I decided to actually fire my own event whenever I wanted to report on the algorithm progress (which is rather lenghty). So I defined my delegate and event inside my one-function class that runs the algorithm: