Image Compression Using Halftoning and Huffman Coding

Halftoning is the printing technology in which each pixel in halftone image is represented by single bit. Hence halftoning gives 87.5% compression ratio. Modified Huffman encoding technique is used on halftone image for further compression of image data. This algorithm achieves a high compression ratio that ensures optimum utilization of network resources and storage. In our earlier work a small operator of size 3x3 is used, which effectively takes only one tap operation. Floyd-Steinberg operator which takes 5 tap operations has been used. Thus factors, like computational complexity, memory space and image quality, have been considered. The proposed algorithm has been implemented on MATLAB platform and has been tested on various images of size 256x256. The image quality measurement has been done using Mean Square Error and Structural Similarity Index parameters. The proposed technique can be used for storage of images in this hybrid compressed form, and low bit rate data transmission for video conferencing.