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NSBitmapImageRep bitmapData contains all zeroes?
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NSBitmapImageRep bitmapData contains all zeroes?


  • Subject: NSBitmapImageRep bitmapData contains all zeroes?
  • From: Nick Forge <email@hidden>
  • Date: Sat, 26 Apr 2008 00:34:39 +1000

I am working on a Computer Vision project that uses real-time image processing. I am grabbing frames using QTKit, then converting the resulting CVImageBufferRef into a CIImage, and then converting that into an NSBitmapImageRep. I know that my resulting NSBitmapImageRep is fine, since I am viewing it by sticking it in an NSImage and then popping that into an NSImageView (the QTKit Capture Preview has a 1/2 second lag time - which is unacceptable for this project). Everything works as it should, but when I go to grab the raw pixel data from the NSBitmapImageRep like so:

unsigned char *bitmapData = [self bitmapData];

(btw it says "self" because this is from a category of NSBitmapImageRep)

The resulting array, bitmapData, is an array of zeroes! Every pixel sample in bitmapData is zero, yet I can draw the image and the image IS there. What's going on? Any suggestions as to what I may be overlooking?

Thanks in advance,
Nick Forge
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