A method of pre-processing a defocused image of an object includes applying an object-based sharpening filter on the defocused image to produce a sharper image; and quantizing the sharper image using block-wise quantization. A system for generating decoded text data from alphanumeric information printed upon an object includes a camera that obtains image data of the alphanumeric information. The system also includes a pre-processor that (a) performs block-wise quantization of the image data to form conditioned image data, and (b) performs optical character recognition on the conditioned image data to generate the decoded text data.