(i) Huffman code:
- Huffman coding is a lossless compression variable length coding technique.
- It is frequency dependant technique.
- In Huffman coding characters that occur most often are assigned few bits while the characters that occur rarely are assigned more bits.
(ii) Lossy predictive coding:
- DPCM is Lossless Predictive Coding.
- In DPCM, Interpixel redundancy exists due to correlation between the neighboring pixels in an image. Spatial redundancy implies that there is a relationship between pixels in an image.
- To reduce the inter-pixel redundancy the difference between adjacent pixels is used to represent an image by DPCM.
(iii) Transform coding
- In transform coding a reversible linear transform is used to map the image into a set of transform coefficients which are then quantized and coded.
- For most images, a significant number of coefficients have small magnitudes and can be coarsely quantized or discarded entirely with little image distortion.