An overview of computer technology in various fields has shortened the job of human beings but has also resulted in huge volume of digital data. Data compression helps us to reduce the given data size without missing the important information. The two types of compression are lossy and lossless compression. In this paper some of the lossy and lossless image compression techniques are discussed in detail. The rudimentary idea of image compression is to diminish the average number of bits per pixel necessary for their depiction. With the help of image compression, the storage space of images can be decreased and also the storage and transmission process is improved in order to save the channel bandwidth. As lossy technique is not reversible, recovering the real image using the lossless compression will be much useful. But in lossless technique the compression ratio is low when compared to lossy image compression technique. In this paper, it is discussed that the lossy techniques are better to compress the images which are given as an input in different image file formats.

Keywords- Compression Techniques, Cosine Transformation, Lossless Compression, Lossy Compression.