A modified JPEG image compression technique

In this paper, a modified implementation of the Baseline Sequential Coding, which is one of the four basic modes of the JPEG (Joint Photographic Experts Group) standard is discussed. This technique is based on the DCT, which is near optimum transfer and entropy coding. The Software implementation of the technique has been done and the results of the dissertation indicate the inverse relationship between compression achieved and the receiver image reconstruction fidelity. A set of quantizers controls the trade-off between quality & compression, which can be used according to the desired application. Though the actual values for the quality (measured In peak signal to noise ratio) and compression ratio vary for different images, in general, the values for a good compromise are psnr of about 30 dB and a compression ratio of about 20 to 25. By using the modified technique, compression ratio of as high as 50 to 100 can be achieved with only a small reduction in psnr. The proposed technique can be implemented without any change in existing JPEG, by adding a DSF at transmitter and reconstruction filter at the receiver.