graphics programming video work

iPhone camera frame grabbing and a real-time MeanShift tracker

Just wanted to report on a breakthrough in my iPhone-CV digging. I found a true realtime frame grabber for the iPhone preview frame (15fps of ~400×300 video), and successfully integrated this video feed with a pure C++ implementation of the MeanShift tracking algorithm. The whole setup runs at realtime, under a few constraints of course, and gives nice results.
Update: Apple officially supports camera video pixel buffers in iOS 4.x using AVFoundation, here’s sample code from Apple developer.
So lets dig in…

3d graphics programming school

Tracing wild rays

I havn’t published in a while. I was back up with work on a project for uni., work and my writing…
But the good thing with keeping busy, is that after a while – you have something to show for! So here’s what i’ve been working on for Comp. Graphics course – A Ray Tracer.

graphics Recommended tips Website work

Beef up your presentations with word clouds

friendshipThere’s nothing like a good visualization to deliver your ideas over a presentation. Concise points and breakdowns can only go a certain distance before they become weary, and finally confuse your audience. It’s better to keep them on their toes by spicing up the boring slides every 5 or so page turns.
I found that Word Clouds, a kind-of new visualization concept, have a good trait of focusing the attention over a single word’s associative space. You bold your main word, center it, and scatter the associative words around it. This creates a powerful effect.
I found a nice tool to create these word coulds on-the-fly: Wordle.
The way I did was, get the Wikipedia value of my word, for example “Friendship“, and go to the Edit tab. Copy all the textarea’s contents, and paste it into Wordle’s word cloud creator. Press “GO” and the results are immediate.
You can eliminate the “outliers” – those unrelated words that appear too many times, and layout the cloud as you like to fit your slide.
The down-side with Wordle is that it has no export ability, so I had to take an Alt-PrintScreen screenshot to get my cloud as a picture.

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:


DIY: Cow skin pattern for your GIMPed cows

I wanted to share with you a (very simple and short) method for creating cow-skin patterns, totally random each time, for your GIMPin needs.
This can actually work the exact same way in GIMP, PS or Paint.NET.
I will demonstrate with GIMP, but it is so simple you can do it in any of the aforementioned programs.
So here goes:


Paint.NET is cool

Today I stumbled upon Paint.NET.
It seems like an awesome tool for quickly drawing stuff.

I also read that some compare it to The GIMP (which I adore…). I found Paint.NET is easier for simpler tasks that the GIMP can drive you nuts while trying to do them.
In the GIMP i find myself using the select tool A LOT. You want to draw a circle? select and fill. You want a simple rectangle? select and fill…
Sometimes I wish GIMP was more like plain ol’ Paint…

Here I think Paint.NET really excels. It keeps the simplicity of Paint, but adding the open-sourceness and variety of GIMP.