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OpenCV Haartraining: Detect objects using Haar-like features

Posted on : 02-06-2009 | By : rhondasw | In : OpenCV

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OpenCV’s standart cascades allow to detect faces and eyes.  I wanted to create cascade in similar way to detect another objects:  pringles or plate for example.  I found some material in Net how to use OpenCV training tools, also I investigated training tool’s source  code myself  to found out, what training parameters can be tuned.

Prepare images.

For training, I needed thousands of images, containing my object with different lightning conditions and perspectives. After trying to find required number of pictures with Google ,  I understood, that it’s really difficult task =).  So I decided to take video with my object,  then I wrote simple program to crop object from video, frame by frame.  In such way,  I generated about 3000 positive samples (cropped images  with my object).  Resolution varied from 50×50 to 100×100.  The advantage of this method – you  get many samples with different reflections, illuminations and backgrounds.  It’s very important, that all these images “features” are various!

“Fixing” the OpenCV’s implementation of Viola-Jones algorithm

Posted on : 10-04-2009 | By : rhondasw | In : OpenCV

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Today’s story is about improving performance of OpenCV library on the ARM-based platforms.

As you already know (from here or from here or may be even from here), face detection algorithm implemented by OpenCV library doesn’t work perfectly on ARM processors. Science doesn’t know for certain why this happens. There might be several possible reasons. One of our assumption was missing of hardware support for floating point operations. So we tried to translate Viola-Jones algorithm from floating point to fixed point. And that’s how we did this…

Getting MJPEG stream from Axis Ip-camera (Axis 211M and Axis 214 PTZ) as a camera device in OpenCV with DirectShow

Posted on : 09-04-2009 | By : Aleksey Kodubets | In : OpenCV

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By default OpenCV 1.1 don’t support AXIS ip-cameras. So, this paper describes approach for getting camera interface (cvCaptureFromCAM) from OpenCV when you are using an Axis Ip camera.

OpenCV vs. Apple iPhone

Posted on : 02-04-2009 | By : rhondasw | In : OpenCV

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This time OpenCV was ported to the Apple iPhone platform.

First of all we need to compile OpenCV library itself so that it can be used on the iPhone. There are two ways here:

1. Use OpenCV as a private framework.
2. Compile OpenCV as a static library.

First approach looks more comfortable for using, though I was not able to make it work properly on the iPhone (it works fine on the simulator, but not on the real hardware).

But anyway, let’s see how both approaches can be followed.

Compiling OpenCV for ARM9 platform

Posted on : 31-03-2009 | By : Yuri Vashchenko | In : OpenCV

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Compiling OpenCV

  • Build platform: Windows XP SP3
  • Target platform: ARM9 fixed point

Contents

  • Download and prepare OpenCV library source code
  • Download and prepare compiler
  • Create/Modify Makefile
  • Compile and link
  • Run and Test
  • Performance
  • Profiling

 

Running OpenCV facedetect sample on Windows CE (Windows Mobile)

Posted on : 31-03-2009 | By : rhondasw | In : OpenCV

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Here is a brief description of compiling and running OpenCV’s facedetect sample on Pocket PC.

Compiling

I used Visual Studio 2005 Team Suite edition to compile OpenCV 1.1 pre 1. It compiled without any trouble for Win32.

Then I tried to compile for Pocket PC (set Platform to Pocket PC 2003 (ARMV4)). Some compilation errors occured. As I only needed to compile a facedetect sample, I decided to compile the necessary files only.

 

Profiling OpenCV

Posted on : 18-03-2009 | By : Yuri Vashchenko | In : OpenCV

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Compiling OpenCV part 2

Compiling without profiling

This time I compiled OpenCV library on Debian Linux installation.

I used VMWare 6.5 and Debian OS linux distribution.

I setup Virtual Machine to allocate 10GB hard drive space and 512 MB of system memory.

I setup the latest version of CodeSourcery G++ toolchain (version arm-2008q3-72-arm-none-linux-gnueabi) downloaded from http://www.codesourcery.com/sgpp/lite/arm. The installation dir was /opt/crosstool/codesourcery

ARM-wrestling with OpenCV

Posted on : 12-03-2009 | By : Igor Stepura | In : OpenCV

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I played with two ARM9-based single board computers (SBC) recently to investigate how OpenCV would operate on embedded platforms. The SBCs are – TS-7800 and SBC2440-III.

OpenCV uses floating point operations a lot, but not all of the ARM processors have FP coprocessor, so developers should use either some FP library, or as in my case – use Linux kernel FP emulation. There are two types of such emulation OABI and EABI. More details can be found here and here. Kernel release 2.6.16 was the first one to include ARM EABI support.

Unfortunately, CPUs of both SBCs do not support floating point in hardware, but luckily enough, TS-7800 has Debian Linux with 2.6.21 kernel. So I had a chance to compare OpenCV performance for OABI and EABI.

Both SBCs have necessary tool-chains in package – TS-7800 has Linux and Windows(Cygwin) tool-chains, SBC-2440 – only Linux one.  In addition to these I downloaded newer release of Codesourcery ARM tool-chain for Windows, because the one from TS-7800 SW package didn’t work properly with Cygwin.