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2007.02.06 10:54 "Re: The fake input in fax2tiff", by John Whitington
Joris,
Quoting Joris <joris.at.lebbeke@skynet.be>:
> John Whitington wrote:
> > I'm modifying the fax2tiff source to decode CCITT streams from PDF
> > files into raw data. Thus, I don't need to produce an output TIFF. It
> > works, but now I'm paring it down by removing the output code.
> >
> > The fake input fax2tiff produces to make the fax input work is
> > initialised in the original source like this:
> >
> > faxTIFF = TIFFClientOpen("(FakeInput)", "w",
> > /* TIFFClientOpen() fails if we don't set existing value here */
> > TIFFClientdata(out),
> > TIFFGetReadProc(out), TIFFGetWriteProc(out),
> > TIFFGetSeekProc(out), TIFFGetCloseProc(out),
> > TIFFGetSizeProc(out), TIFFGetMapFileProc(out),
> > TIFFGetUnmapFileProc(out));
> >
> > (Where 'out' is the TIFF pointer being used for output).
> >
> > How can I synthesize the values (TIFFClientdata etc.) without having
> > to open an actual output TIFF?
>
> Perhaps I'm misunderstanding, but it seems to me there is a much easier
> approach. Work out a fake file header and fake IFD that for convinience you
> place right after the file header. Make the fake IFD have all appropriate
> settings for this kind of file, like appropriate Photometric and Compression
[snip details]
> Or am I missing something?
fax2tiff works below the normal API level for libtiff, as far as I can see
(which is why it directly references tiffiop.h and tif_config.h). The paramaters
being generated in the original fax2tiff code I quote above are completely
wrong, they're just non-NULL, to avoid the call to TiffClientOpen failing, The
parameters themselves will never be called.
So I suppose I can rephrase: What's the easiest way to make non-NULL parameters
of suitable types?
As you can guess, I'm not a C programmer! (I'm interfacing this code to another
language)
--
John Whitington