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    <p>Assuming you want to do this in real time (rather than using a screen capture, which you specifically say you <em>don't</em> want):</p> <p>You first need to be capturing the video buffer <strong><a href="http://developer.apple.com/library/ios/#qa/qa1702/_index.html" rel="noreferrer">as outlined by Apple here</a></strong>. </p> <p>Then you can do what you like with the <code>CMSampleBufferRef</code>. Apple's sample app makes a <code>UIImage</code>, but you can simply copy it across into an <code>unsigned char</code> pointer (via a <code>CVImageBufferRef</code> or <code>CVPixelBufferRef</code>) and then pull the BGRA value of the pixel in question, something like this (untested code: example is for the pixel at 100x,200y):</p> <pre><code>int x = 100; int y = 200; CVPixelBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); CVPixelBufferLockBaseAddress(imageBuffer,0); tempAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer); size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); size_t width = CVPixelBufferGetWidth(imageBuffer); size_t height = CVPixelBufferGetHeight(imageBuffer); CVPixelBufferUnlockBaseAddress(imageBuffer,0); int bufferSize = bytesPerRow * height; uint8_t *myPixelBuf = malloc(bufferSize); memmove(myPixelBuf, tempAddress, bufferSize); tempAddress = nil; // remember it's BGRA data int b = myPixelBuf[(x*4)+(y*bytesPerRow)]; int g = myPixelBuf[((x*4)+(y*bytesPerRow))+1]; int r = myPixelBuf[((x*4)+(y*bytesPerRow))+2]; free(myPixelBuf); NSLog(@"r:%i g:%i b:%i",r,g,b); </code></pre> <p>This gets the position relative to the pixels of the video feed itself, which may not be what you want: if you want the position of the pixel as displayed on iPhone's display, you may need to scale this.</p>
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    1. POHow can I get RGB value of pixcel at specified point on the cammera screen?
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    1. COI stumbled on this great explanation. Thank you. Can you elaborate on the "A" of the BGRA. I have seen a lot of code trying to normalize for the A before analyzing the BGR. Can you explain on why the normalizing process before using the BGR data. Thanks
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    2. COIt's the alpha. Which, in the case of a video frame buffer such as this, is always 100% and so can be ignored (it's just that iOS operates in a 32-bit color space even when it doesn't really need to).
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