Explain JPEG Compression Process with relevant figures
In multimedia, different signals we measure for digitization are either time-varying (audio) or space-varying (image) or vary with both time and space (video). The number of times a time-varying periodic signal changes during a unit of time is the frequency of the signal. Similarly for a space-varying signal such as the colour intensities of pixels in an image, frequency or more specifically spatial frequency is the number of times the intensities varies over a unit of distance.
The component frequency and amplification for each frequency can be computed for an image using Fourier Transform and it can be displayed graphically in the Frequency Domain. The horizontal axis represents frequency and the vertical axis represents amplitude in such a frequency spectrum graph – The spikes at different frequencies correspond to different signal components.
JPEG Compression Process:
The JPEG encoder works following the steps listed below:
Step1: Transform RGB to YIQ or YUV and subsample colour.
Step2: Perform DCT on image blocks.
Step3: Apply quantization.
Step4: Perform zigzag ordering and run-length encoding.
Step5: Perform entropy coding.