Lossless Compression

In applications where preservation of the original image is important, lossless compression provides a
reversible method of compression for identical original and reconstructed images.  These methods in codecs generally requires trade-off in coding efficiency, coding complexity and coding delay.  Figure 3 depicts the three dimensions.

A lossy compression is also called a irreversible compression because the amount of data loss between the original and reconstructed image.  The choice for trade-offs in lossy compression based codecs adds one more dimension than the dimensions of lossless compression; namely signal quality.  Figure 4 shows the four dimensions. Because of this extra degree of freedom, a lossy compression scheme can yield higher compression ratio than lossless compression scheme.