1. An electronic system comprising: an image capturing device operable for capturing a first live image; and a comparator coupled to said image capturing device and operable for generating a feedback signal by comparing said first live image with a reference image and for adjusting at least one setting of said image capturing device by said feedback signal, wherein said comparator is configured to determine a first matching percentage by comparing said first live image with said reference image, wherein said image capturing device is configured to capture a second live image after said at least one setting of said image capturing device is adjusted, and wherein said comparator is configured to determine a second matching percentage by comparing said second live image with said reference image.