As camera phones have permeated into our everyday lives, two dimensional (2D) barcode has attracted researchers and developers as a cost-effective biquitous computing tool. A variety of 2D barcodes and their applications have been developed. Often, only monochrome 2D barcodes are used due to their robustness in an uncontrolled operating environment of camera phones. However, we are seeing an emerging use of color 2D barcodes for camera phones. Nonetheless, using a greater multitude of colors introduces errors that can negatively affect the robustness of barcode reading. This is especially true when developing a 2D barcode for camera phones which capture and store these barcode images in the baseline JPEG format. This paper presents one aspect of the errors introduced by such camera phones by modeling the camera phone capture channel for JPEG color barcode images wherein there is camera auto-focus.
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