An image is compared to a validation image to obtain a signal-to-noise ratio. The signal-to-noise ratio is used to determine validity of the image. According to an embodiment, the image includes a barcode. According to another embodiment, a minimum threshold value for the signal-to-noise ratio is set and the validity of the image is determined based on the minimum threshold value and the signal-to-noise ratio. The minimum threshold value can be determined by using respective signal-to-noise ratios resulting from comparing a valid image to a validation image and an invalid image to a validation image.