Windows Phone 8 HaarCascadeDetector

[DRybochkin]

Hi Anders,

I have the exception "Handle is not pinned" at last row of the next code

Exception

at System.Runtime.InteropServices.GCHandle.AddrOfPinnedObject() at Accord.Imaging.IntegralImage2..ctor(Int32 width, Int32 height, Boolean computeTilted) at Accord.Imaging.IntegralImage2.FromBitmap(UnmanagedImage image, Int32 channel, Boolean computeTilted) at Accord.Vision.Detection.HaarObjectDetector.ProcessFrame(UnmanagedImage image)

Code:

System.IO.Stream stream = System.IO.File.OpenRead("Resources/haarcascade_frontalface_default.xml");
System.Xml.XmlReaderSettings settings = new System.Xml.XmlReaderSettings();
settings.XmlResolver = null;
settings.DtdProcessing = System.Xml.DtdProcessing.Parse;
HaarCascade cascade = HaarCascade.FromXml(stream);

HaarObjectDetector detector = new HaarObjectDetector(cascade);
detector.SearchMode = ObjectDetectorSearchMode.Default;
detector.ScalingMode = ObjectDetectorScalingMode.GreaterToSmaller;
detector.ScalingFactor = 1.5f;
detector.UseParallelProcessing = false;
System.Drawing.Rectangle[] rects = detector.ProcessFrame(img2);

Thanks in advance Dmitry

[cureos]

@DRybochkin I am looking into this issue right now, although I am currently struggling with a parsing problem... (I can workaround the parsing problem for now, but I want to flag this separate issue as well.)

@cesarsouza Have you noticed that the Haar Cascade XML files in Open CV has recently changed their format? Please see this commit.

[cureos]

I have now debugged the code, and the GCHandle is successfully allocated with type Pinned, but then the AddrOfPinnedObject method still interprets the handle as not Pinned?

I need to investigate further whether this is a bug in the PCL/Phone adaptation of Accord, or whether it is an issue with Windows Phone's own class libraries. Stay tuned :-)

[DRybochkin]

@cureos this code works on pure WP8, but don't work in PCL lib

        this.nSumImage = new int[nHeight, nWidth];
        this.nSumHandle = GCHandle.Alloc(nSumImage, GCHandleType.Pinned);
        IntPtr ip = nSumHandle.AddrOfPinnedObject();

[DRybochkin]

I think it somehow connected with redefining System.Runtime.InteropService

[cureos]

Yes, this is most likely the issue. I am currently searching the PCL version for inconsistencies, I'll get back as soon as I know more.

[DRybochkin]

Change GCHandleType.cs in Portable.System on next

public enum GCHandleType
{
    Weak = 0,
    WeakTrackResurrection = 1,
    Normal = 2,
    Pinned = 3,
}

and it will work

[cureos]

That was exactly what I was testing when I saw your latest post :-)

I will provide the update and new binaries as soon as possible. Thanks for all your help with reporting and investigating this.

Best regards, Anders

[DRybochkin]

You are welcome! Did you know the library in C# automatic generation haarcascade.xml from positive & negative images?

[cureos]

Now I have added the correction to the GCHandleType enum in the aforge repository, and I have also replaced the Accord binaries for version 2.12.0.1 with binaries built with the Pinned correction in place (I hope this should be enough).

Again, a big thank you for pointing out the issue and helping me solve it! Anders

PS. I was not aware of the XML generation functionality. I have not yet explored Accord in all the details. But it's good to know. Thanks!