Getting Pixel Data From CIImage
Getting Pixel Data From CIImage
- Subject: Getting Pixel Data From CIImage
- From: "Bridger Maxwell" <email@hidden>
- Date: Mon, 12 May 2008 21:06:08 -0400
Hey,
I am trying as hard as I can to get pixel data from a CIImage, but am
failing, pretty miserably. I am using
render:toBitmap:rowBytes:bounds:format:colorSpace: from CIContext and
it seems to work, but doesn't really. I get data in my int*
pointer, but it never changes! What am I doing wrong? I posted my
code. The part in need of assistance is near the bottom of
(void)captureOutput. I would greatly appreciate your help.
Thank You,
Bridger Maxwell
- (void)captureOutput:(QTCaptureOutput *)captureOutput
didOutputVideoFrame:(CVImageBufferRef)videoFrame
withSampleBuffer:(QTSampleBuffer *)sampleBuffer
fromConnection:(QTCaptureConnection *)connection
{
CIImage* image = [CIImage imageWithCVImageBuffer:videoFrame];
[monoChromeFilter setValue:image forKey:@"inputImage"]; //First we
monochrome it (only black and white
//[smoothingFilter setValue:[monoChromeFilter
valueForKey:@"outputImage"] forKey:@"inputImage"];
if (needsNewBackground) { //If the flag has been raised we will
capture a new background
[backgroundFilter setValue:[monoChromeFilter
valueForKey:@"outputImage"] forKey:@"inputBackgroundImage"];
if (videoDeviceInput) {
needsNewBackground = NO;
}
}
[backgroundFilter setValue:[monoChromeFilter
valueForKey:@"outputImage"] forKey:@"inputImage"]; //Now we subtract
the background from the monochrome image
[colorCorrectionFilter setValue:[backgroundFilter
valueForKey:@"outputImage"] forKey:@"inputImage"];
CIImage* finalImage = [colorCorrectionFilter valueForKey:@"outputImage"];
size_t rowBytes = [self optimalRowBytesForWidth:[finalImage
extent].size.width bytesPerPixel:4];
int* imageData;
[[[NSGraphicsContext currentContext] CIContext] render:finalImage
toBitmap:imageData rowBytes:rowBytes
bounds:[finalImage extent]
format:kCIFormatARGB8
colorSpace:CGColorSpaceCreateWithName(kCGColorSpaceGenericGray)];
blobDetector->computeBlobs(imageData);
NSLog(@"On Frame %i there are %i blobs. Sample byte 5:
%i",frameCount++,blobDetector->getBlobNb(),imageData[19]);
[outputView setImage:finalImage];
[outputView setNeedsDisplay:YES];
//CIContext* theContext = [outputView ciContext];
}
- (void) drawBlobsOnCIImage:(CIImage *)image {
for (int n=0 ; n< blobDetector->getBlobNb() ; n++)
{
*blob = blobDetector->getBlob(n);
if (blob->isOk())
{
NSRect rectangle = NSMakeRect(blob->xMin, blob->yMin, blob->xMax -
blob->xMin , blob->yMax - blob->yMin);
}
}
}
- (size_t)optimalRowBytesForWidth: (size_t)width bytesPerPixel:
(size_t)bytesPerPixel
{
size_t rowBytes = width * bytesPerPixel;
//Widen rowBytes out to a integer multiple of 16 bytes
rowBytes = (rowBytes + 15) & ~15;
//Make sure we are not an even power of 2 wide.
//Will loop a few times for rowBytes <= 16.
while( 0 == (rowBytes & (rowBytes - 1) ) )
rowBytes += 16;
return rowBytes;
}
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