Use jpeg_mem_src/jpeg_mem_dst instead of save to tempfile hack

[GoogleCodeExporter]

Currently pixReadMemJpeg and pixWriteMemJpeg fails on windows due to /tmp/... 
not being a valid path and fmemopen not existing. However there isn't much 
reason for that hack anymore anyways as we could just use jpeg_mem_src and 
jpeg_mem_dst (at least when using libjpeg 8 or newer).

Original issue reported on code.google.com by poiza...@gmail.com on 18 Sep 2013 at 1:02

[GoogleCodeExporter]

[deleted comment]

[GoogleCodeExporter]

In 1.70 (which should come out RSN -- I keep saying that), we're using

    fp = tmpfile();
    fwrite(cdata, 1, size, fp);

This has two advantages over the 1.69 implementation: it works on Windows and 
it's secure against hacking where someone is able to guess the filename.

I agree it would be nicer not to have to write to a file, and when jpeglib8 has 
attained widespread adoption it would make sense to require it.  I see that 
people are still having issues with detecting availability of these functions 
using config files; e.g.,
   http://comments.gmane.org/gmane.comp.kde.devel.graphics/307

So let's consider this resolved for now.  You can put those lines in to patch 
for pixReadMemJpeg().  Here's the code to patch pixWriteMemJpeg():

    fp = tmpfile();
    ret = pixWriteStreamJpeg(fp, pix, quality, progressive);
    rewind(fp);
    *pdata = l_binaryReadStream(fp, psize);

~          

Original comment by dan.bloo...@gmail.com on 21 Sep 2013 at 1:22

• Changed state: Accepted

[GoogleCodeExporter]

Could we add a HAS_JPEG_MEMIO config or something like that so we could enable 
it manually even if we can't detect the availability? I can create a patch if 
interested.

Original comment by poiza...@gmail.com on 24 Sep 2013 at 11:20

[GoogleCodeExporter]

Let's not.  I believe these mem functions are in version 9, which I've never 
even tried.  And as I said before, I want to limit the amount of #if 
configuration code because it becomes a real headache to support even on one 
platform, let alone on several.  Generality is nice, but robustness is 
mandatory.

Original comment by dan.bloo...@gmail.com on 4 Oct 2013 at 9:51

[GoogleCodeExporter]

The mem functions were introduced in version 8 according to the changelog which 
was released back in january 2010.

Original comment by poiza...@gmail.com on 7 Oct 2013 at 12:28

[GoogleCodeExporter]

1.70 is out.  The temp file issue should be resolved on windows.  Not 
proceeding further on the memio config change that you proposed.  If you want 
to give me a patch, we can consider it for a future release.

You can get 1.70 at leptonica.org/download.html.

Original comment by dan.bloo...@gmail.com on 23 Jan 2014 at 8:58

• Changed state: Fixed