Re: [pdf-devel] DCT filter: suspending or buffering

[jemarch]

Hi Yang.

   Normally, the data feeding to libjpeg decompressing is done in a
   callback function (in which way I think pdf might take...). That means
   there is no chance to return a ENINPUT to outer loop to get more input
   data so we need a internal buffer to cache all compressed data and put
   them into libjpeg.I don't know wether it's acceptable.I mean, if there
   is very huge jpeg pic...

   Or, there is a another mode of I/O of libjpeg, suspending in which the
   decompressing will return if it needs more input.But the document says
   there may be a performance issue in this mode.No promise of the running
   time.

   I'm proceeding along to the first choice.I think maybe we can adjust pdf
   I/O interfaces or implement both of the modes of libjpeg without
   changing our interface.

We definitely want to use the suspended mode, using jpeg_read_header,
jpeg_start_decompress, etc. We should avoid to store the entire
contents of a PDF stream in memory: these streams can become really
big!.

Don't worry about the performance issue.