blah.m

- (CVPixelBufferRef) pixelBufferFromCGImage:(CGImageRef) image {
  NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                           [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                           [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
                           nil];
  CVPixelBufferRef pxbuffer = NULL;

  int width = 640;
  int height = 480;
  CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault,
                                        width,
                                        height,
                                        kCVPixelFormatType_32ARGB,
                                        (CFDictionaryRef) options,
                                        &pxbuffer);
  // NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

  CVPixelBufferLockBaseAddress(pxbuffer, 0);
  void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
  // NSParameterAssert(pxdata != NULL);

  CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef context = CGBitmapContextCreate(pxdata,
                                               width,
                                               height,
                                               8,
                                               4 * width,
                                               rgbColorSpace,
                                               kCGImageAlphaNoneSkipFirst);
  // NSParameterAssert(context);
  // CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
  CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);
  CGColorSpaceRelease(rgbColorSpace);
  CGContextRelease(context);

  CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

  return pxbuffer;
}