qpdf: image /Im1 on page 1: optimizing image reduces size from 768000 to ...
qpdf: image /Im1 on page 2: not optimizing because unable to decode data or data already uses DCT
qpdf: image /Im1 on page 3: optimizing image reduces size from 768998 to ...
qpdf: image /Im1 on page 4: optimizing image reduces size from 576000 to ...
qpdf: image /Im1 on page 5: not optimizing because unable to decode data or data already uses DCT
qpdf: image /Im1 on page 6: optimizing image reduces size from 641497 to ...
qpdf: image /Im1 on page 7: optimizing image reduces size from 192000 to ...
qpdf: image /Im1 on page 8: not optimizing because unable to decode data or data already uses DCT
qpdf: image /Im1 on page 9: optimizing image reduces size from 3001 to ...
qpdf: wrote file a.pdf
