Bug with large images

Hi.

I am preparing maps with Magick++ (ImageMagick 6.3.0
11/06/06 Q8).

I am creating G4 TIFF images which are more than
10k x 10k pixels (A0/A1 at 600 DPI).
Because of the image size I render the image strip by strip.
A slingle strip is at most 200MB in size (on a machine with
1GB RAM).

When the width of a strip is larger than around 9999 pixels,
strange things start happening:

     - rendering slows down painfully (75min instead of
5min)
     - ghost lines are drawn: in each strip there are
several
       ghost lines coming from the top-left corner of the
strip
       (examples attached).
     - if I do not clip the polylines (some are much bigger
than
       the map) imagemagick requests a block of memory of
around
       500MB and sometimes crashes.
       (If I clip the polylines to a rectangle that is twice
the size
        of the image and then no additional memory is
requested).

I thought the slowness and the ghost images were caused by
arcs in
paths, but after disabling them, the program was again slow
on strips
wider than 9999 pix and I didn't wait for it to finish.

The attached images show parts of a good map at 500DPI(width
8859pix)
and a bad map at 600DPI (width 10630pix) with the same
detail and the
top-left part of a strip.

Marko Mahnič

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