You have to properly configure your QTVideoContext to get this.
By default, most of the CoreVideo sample code uses
QTOpenGLTextureContextCreate(), and so, you get CVOpenGLTextureRef.
If you want to retreive CVPixelBuffers, you have to create your
QTVisualContext using the QTPixelBufferContextCreate() function instead.
And when you create this kind of context, you have to configure the
expected pixel format too.
The following sample show you how to configure this kind of context
and how to access pixel data:
http://developer.apple.com/samplecode/QTPixelBufferVCToCGImage/listing1.html
Le 6 mai 08 à 17:08, Raphael Sebbe a écrit :
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 PROTECTED]>:
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 PROTECTED]
>
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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