How does using DCT help in image compression I once learnt that the Huffman Encoding is used to rid of redundant information, thus reducing file size. I am not sure how using a DCT, or FFT on an image can help in reducing file size. It does not work on redundancy, then how does it reduce the total amount of data?
If you take an image as is (especially a photograph, as opposed to line art, a document scan...), there's very little redundancy in it for Huffman encoding to do its work - because the image contains many small fluctuations and details which are not perceptible to the human eye but nevertheless present in the data. DCT followed by coefficient truncation/quantization eliminates the barely perceptible details and creates redundancy for Huffman compression to work on.