- Coefficient Quantization
- Lossless Compression
The JPEG lossy compression algorithm consists of three successive
stages, shown in the flow chart below.
DCT Transformation --> Coeff Quantization -->
Both DCT transformation and the final compression of the
quantized data are, for the most part, lossless procedures (negligible precision may be
lost during DCT transformation due to minor numerical round-offs). This leaves the
coefficient quantization phase as the driving force behind JPEGs overall
"lossyness". It is in this step that insignificant data concerning the image is
discarded. All three stages are described next.