iOS UIImage -> NSData

NSData *imageData = UIImagePNGRepresentation(image);

- (CGContextRef)CreateRGBBitmapContext:(CGImageRef)inImage
{
    CGContextRef    context = NULL;
	CGColorSpaceRef colorSpace;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;
	
	size_t width = CGImageGetWidth(inImage);
	size_t height = CGImageGetHeight(inImage);
	bitmapBytesPerRow   = (width * 4);
    bitmapByteCount     = bitmapBytesPerRow * height;
	
	colorSpace = CGColorSpaceCreateDeviceRGB();

	if(processData == nil)
	{
		processData = malloc(bitmapByteCount);
		memset(processData, 0, bitmapByteCount);
	}
	else
	{
		memset(processData, 0, bitmapByteCount);
	}
	
    if (processData == NULL) 
    {
        return NULL;
    }

	if (colorSpace == NULL)
    {
		CGColorSpaceRelease( colorSpace );
        return NULL;
    }
	
	size_t bitsPerComponent = 8;
	context = CGBitmapContextCreate (processData, 
									 width, 
									 height,	
									 bitsPerComponent,
									 bitmapBytesPerRow, 
									 colorSpace, 
									 kCGImageAlphaNoneSkipFirst);
	
	CGColorSpaceRelease( colorSpace );
	if (context == NULL)
    {
        free (processData);
    }
    return context;
}


CGContextRef cgContext = [self CreateRGBBitmapContext:originalImage.CGImage];
	if(cgContext == NULL)
	{
		return nil;
	}
	
    size_t w = CGImageGetWidth(originalImage.CGImage);
    size_t h = CGImageGetHeight(originalImage.CGImage);
    CGRect rect = {{0,0},{w,h}}; 
    CGContextDrawImage(cgContext, rect, originalImage.CGImage); 
	void *data = CGBitmapContextGetData (cgContext);

       // do something with data
       ...

}