quantized DCTcoefficients jpeg images

[apan]

Is there a reliable method to extract the quantized DCT coefficients of a jpeg image? I can see that there is the jpeglib for manipulation of jpegs but I am wondering if someone has already used it and does the job I want to do. To extract the quantized DCT coefficients of each 8x8 block of a jpeg image. (As a matter of fact we are talking - I think - about decompression of a jpeg.) Any other solutions that may apply are fine too. Thanks.
PS: I am trying to do a steganography project here...