[pdftex] graphic{s,x} PNG + pdflatex bug

[George N. White III]

On Thu, May 6, 2010 at 2:41 PM, Martin Heller <mr_heller at yahoo.dk> wrote:
> On 2010-05-06 16:31, Nico Schlömer wrote:
>>
>> Hi all,
>>
>> I experienced a weird bug using \includegraphics of the graphicx
>> package with pdflatex 1.40.10.
>>
>> I try to load the attached PNG file, and unlike with other PNG files,
>> pdflatex would just bail out with
>>
>> ==================== *snip* ====================
>> [...]
>> [Loading MPS to PDF converter (version 2006.09.02).]
>> )
>> ! Dimension too large.
>> <argument>  \wd \@tempboxa
>> l.7 \includegraphics{img1.png}
>> ?
>> ==================== *snap* ====================
>>
>> David Carlisle, maintainer of graphicx, suggests that may be a bug in
>> pdflatex -- What do you reckon?

Actually, the "! Dimension too large" is accurate here.

> Your image has a rather odd resolution.
>
> Image: img1.png
>  Format: PNG (Portable Network Graphics)
>  Class: DirectClass
>  Geometry: 250x250+0+0
>  Resolution: 0.39x0.39
>  Print size: 641.026x641.026
>  Units: PixelsPerInch
>
> So your png is 250/0.39 = 641.026 in wide.
>
> That is 46153 pt which is larger than \maxdimen. Change the resolution and
> your image works fine with \includegraphics.

Saving with Photoshop doesn't affect the above values, but does add
PNG VirtualPage Tags (vpAg in pngcheck):

Index	Tag Name	
0	VirtualImageWidth
1	VirtualImageHeight
2	VirtualPageUnits	

Since the Photoshopped image works, it seems that pdftex uses
the vpAg values when present in preference to the pixel sizes.

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia