Re: [Pan-users] Re: Previews gone screwy

[Darren Albers]

On Sun, 2007-10-21 at 21:50 +0000, Greg Lee wrote:
> On Sat, 20 Oct 2007 17:07:14 +0000, walt wrote:
> 
> > On Fri, 19 Oct 2007 23:39:25 -0400, Dave Chand wrote:
> > 
> >> On Oct 6, 2007, at 6:58 PM, Greg Lee wrote:
> >> 
> >>> I looked at some other 1 part images in this same newsgroup and found
> >>> that all those with byte size <= 369052 displayed correctly, but all
> >>> those with byte size >= 369361 displayed incorrectly...
> > 
> >> I have been experimenting with gdk-pixbuf. What I find is the
> >> following: in the file gtk+2.12.x/gdk-pixbuf/io-jpeg.c there is the
> >> statement #define JPEG_PROG_BUF_SIZE 65536
> >> if you change its value to something significantly higher, such as
> >> #JPEG_PROG_BUF_SIZE 500000
> >> then it seems the decoding problems go away.
> > 
> > I just sent this question to Matthias Clasen, who increased that number
> > from 4096 back in 2002.  It seems that a pixbuf sets an arbitrary size
> > limit on how much data can be loaded in a single chunk.  The real
> > question is whether that limit is intentional or merely a bug.
> > 
> > Meanwhile, Brian Downing posted a patch to the pan bugreport:
> > http://bugzilla.gnome.org/attachment.cgi?id=96917&action=view
> > 
> > His patch explicitly limits the amount of data Pan sends in one chunk,
> > and this is the correct fix at least until we know if this size problem
> > is a gdk bug or not.
> 
> I tried viewing an 8.5M jpeg using Dave's gtk+ patch
> and it did not display correctly.  Also, I increased
> JPEG_PROG_BUF_SIZE further to 1000000, but it still
> didn't work right.  Then I tried Brian Downing's patch
> on the SVN 324 version of pan2, and that worked fine for
> the large jpeg.
> 
> I don't think this is going to surprise anyone, but I
> thought you might like confirmation.
> 


For those that use my Ubuntu packages I plan on uploading a version with
this patch later tonight or tomorrow.