An image sensor includes a pixel array unit including an active pixel area including active pixels, a first dark area including first dark pixels, and a second dark area including second dark pixels, an offset extractor configured to extract a final dark offset value, and a corrector configured to correct pixel data values of the active pixels based on the final dark offset value. The offset extractor extracts a per-column dark offset value, a global dark offset value, a per-row average, and a per-row noise value, selects one of the extracted per-column dark offset value and global dark offset value, and extracts the final dark offset value from the per-row noise value and either the per-column dark offset value or the global dark offset value.