Image compression models

to reduce the size of the image

1. IMAGE COMPRESSION MODELS By Priyadharshini.M

2. Deals with reducing amount of data required to represent a digital image. The reduction process is the removal of redundant data. Compressed image is decompressed to reconstruct the original image. Data compression → reducing amount of data required to represent in a quality of information. Image Compression

3. Two distinct structures: Encoder : An input image f( x,y ) is fed into the encoder which creates the set of symbols from the input data . Decoder : The encoded information is fed into decoder where reconstructed output image f( x,y ) is generated. Image Compression Models

4. General Compression System Model f( x,y ) f( x,y ) Encoder Decoder Removes input redundancy Increases noise immunity Transmitting encoded image Inverse operations of source encoder

5. Three stages of encoding process: Mapper : Transforms input data format designed to reduce interpixel redundancies in the input image. Reversible operation. May or may not reduce the amount of data required to represent the image. The Source Encoder

6. Quantizer : Reduces the accuracy of the mappers output. Reduces the psychovisual redundancies of the input image. Not reversible operation. It must be omited when error free (lossless ) compression is desired. Second stage

7. Symbol encoder : Creates a fixed-or variable length code to represent the quantizer’s output. Maps the output in accordance with the code. In most cases variable length code is used. Reversible operation. Third and final stage

8. It contains two components: A symbol decoder. Inverse mapper . Performs in reverse order . The inverse operations of the source encoder symbol encoder and mapper blocks. The inverse for the quantizer has been left out. Source Decoder

9. Source Encoder f( x,y ) → →Channel To reduce the interpixel redundancies Reduces the accuracy of the mappers output. Represents the quantizer output

10. Source Decoder Channel f( x,y ) Inverse operations of source encoder and mapper blocks.

11. Thank you…