Re: Blob Detection with Core Image
Re: Blob Detection with Core Image
- Subject: Re: Blob Detection with Core Image
- From: "Raphael Sebbe" <email@hidden>
- Date: Tue, 6 May 2008 17:08:07 +0200
I understand, processing is made on CPU anyway. The overhead you get is
because you duplicate (or redraw) the image before processing it.
I believe you actually get a CVImageBufferRef from QTKit, not a CIImage,
which resides in memory (not VRAM, as it comes from a camera anyway). You
could get access to pixel data that way:
CVPixelBufferLockBaseAddress
CVPixelBufferGetBaseAddress
CV...Unlock...
Avoiding unnecessary copy. This is not tested.
Raphael
2008/5/6 Bridger Maxwell <email@hidden>:
> I think I was unclear on where I was lost. I didn't think that I would be
> able to use the OpenTouch blob detection framework, because I couldn't
> pass
> it a CIImage, and converting the CIImage to an NSBitMapImageRep was too
> slow. The only way to pass the image data to the blob detection library
> was
> through the function:
>
> void computeBlobs(int *pixels);
>
>
> Therefor I thought that I would have to work with the CIImage only,
> perhaps
> by making a CIFilter. How would the ObjC wrapper work? Oh, and I think the
> Cocoa app which you are seeing with the OpenTouch source is actually the
> one
> I am working on right now, I have access the the svn. :)
> Thank You,
> Bridger Maxwell
>
> On Tue, May 6, 2008 at 3:50 AM, Mike Abdullah <email@hidden>
> wrote:
>
> > This seems an awful lot of work to me for little gain. If you check out
> > the OpenTouch source, they have an example Cocoa app which really
> requires
> > very little extra work. I think you'd be far better off writing an ObjC
> > wrapper than creating your own entirely separate framework. Paweł would
> > quite likely be happy to even incorporate it into the framework.
> >
> > Mike.
> >
> >
> > On 6 May 2008, at 08:33, Bridger Maxwell wrote:
> >
> > Hello,I am trying to write a program that will detect bright "blobs" of
> > > light in an image and then track those blobs of light. I would be a
> > > Cocoa
> > > version of OpenTouch at http://code.google.com/p/opentouch/. I am
> > > wondering
> > > the best way to do this sort of image processing with Cocoa
> frameworks.
> > >
> > > I have a started this app and use QTKit Capture to grab video from the
> > > webcam. I get my images through QTCaptureDecompressedVideoOutput as a
> > > CIImage. I can apply some filters to the images and display them in a
> > > OpenGLView, but I don't know how I should implement the blob tracking.
> > > From
> > > experience, making an NSBitmapImageRep from the CIImage so I can work
> > > with
> > > the image data is far too slow, so I can't work with the blob
> detection
> > > library used in OpenTouch. Is it possible, or recommended, to
> implement
> > > the
> > > blob tracking as a CIFilter?
> > >
> > > I read through CIColorTracking sample code, which is very close to
> what
> > > I
> > > want to do. However, CIColorTracking simplifies the areas of interest
> > > down
> > > to one location (where to place the duck). I am having trouble seeing
> > > how it
> > > could be adapted to track more than one blob of light. Is it possible
> to
> > > make a CIFilter that would have an output NSArray containing the
> points
> > > where the blobs were found? I could see how it would be possible to
> > > simplify
> > > the image down to an alpha mask of the blobs, but don't know how I
> would
> > > extract the number of blobs and location of each from that image.
> Also,
> > > getting the size of the blob would be desirable.
> > >
> > > I have done a lot of reading and don't seem to be getting anywhere.
> Some
> > > advice on how to proceed would be greatly appreciated.
> > >
> > > Thank You,
> > > Bridger Maxwell
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