objective c - Get pixel colour from a Webcam -

i trying pixel colour image displayed webcam. want see how pixel colour changing time.

my current solution sucks lot of cpu, works , gives me correct answer, not 100% sure if doing correctly or cut steps out.

- (ibaction)addframe:(id)sender {     // recent frame     // must done in @synchronized block because delegate method sets recent frame not called on main thread     cvimagebufferref imagebuffer;      @synchronized (self) {         imagebuffer = cvbufferretain(mcurrentimagebuffer);     }      if (imagebuffer) {         // create nsimage , add movie         // think can remove steps here, not sure where.         nsciimagerep *imagerep = [nsciimagerep imagerepwithciimage:[ciimage imagewithcvimagebuffer:imagebuffer]];         nssize n = {320,160 };         //nsimage *image = [[[nsimage alloc] initwithsize:[imagerep size]] autorelease];         nsimage *image = [[[nsimage alloc] initwithsize:n] autorelease];         [image addrepresentation:imagerep];         cvbufferrelease(imagebuffer);           nsbitmapimagerep* raw_img = [nsbitmapimagerep imagerepwithdata:[image tiffrepresentation]];         nslog(@"image width %f", [image size].width);         nscolor* color = [raw_img coloratx:1279 y:120];          float colourvalue = [color greencomponent]+ [color redcomponent]+ [color bluecomponent];         [graphview setxy:10 andy:200*colourvalue/3];      nslog(@"%0.3f", colourvalue); 

any appreciated , happy try other ideas. guys.

there couple of ways made more efficient. take @ imagefromsamplebuffer: method in this tech q&a, presents cleaner way of getting cvimagebufferref image (the sample uses uiimage, it's practically identical nsimage).

you can pull pixel values straight out of cvimagebufferref without conversion. once have base address of buffer, calculate offset of pixel , read values there.