A Performance Analysis of Different Scanning Paths on Lossless Image Compression for Radiographic Welding Images

Image compression plays a major role in saving bandwidth and memory space which is the need of hour. In industry various components are tested effectively using NDT (Non-Destructive Testing) and this information is stored in the system. To reduce the memory space required for storing, lossless compression is used. This paper focuses on the various scanning paths methods for lossless compression like spiral, cross, raster, snake, peano and zigzag. These methods are compared on the basis of activity measure, average run length and sum of differences and the result of each method is sent to the Run Length Encoding (RLE) and Huffman for compression. Four different methods are used for compression of the images. In the first method, the binary value of the image is taken directly for compression. In the second method, the binary values are converted into corresponding gray values, before compression. In the third method, the binary bit plane is taken for compression. In the fourth method, the gray code bit plane is taken for compression. The above obtained results are compared with the results from calculation of efficiency parameters. Out of the different scanning methods, spiral and peano performed better than the other methods. Thus, the optimal scanning path for welding radiographic images was identified thereby reducing the bandwidth and can be used for lossless compression which achieves more compression ratio.