Accurate localization of four extreme corners for barcode images captured by mobile phones

In this paper, we propose a novel method to locate the four extreme corners of barcodes in the images captured by mobile phones. To achieve this goal, the two nearly-parallel outer boundary lines are firstly localized by utilizing the prior knowledge of the relative distances and angles between the lines, which are subsequently employed to obtain the initially localized corners. A novel post-localization process based on edge tracing is also proposed to further validate the initially localized corners. This is achieved by setting the constraints in maximum direction change when tracing from the current to the next candidate corners. The distinctive feature of the proposed algorithm lies in the capability of handling those curved barcode images taken by the mobile phones. Experiments conducted on a data set of 1410 images show the accuracy of the corner localization is about 92.3% and 90.5% for indoor and outdoor barcode images, respectively. The processing time taken is about 0.8 second using Matlab.