Re: Quickest way to determine if jpg image has QRCode present...

[Sean Owen]

The fastest way is to try to decode it. These are really the same question... how can you know there is no decodable barcode until you look for it.  If you assume it's black and white I suppose you could try something like looking for a region with low chroma values but that's probably slower and less accurate. Scanning takes well under a second.