Well, that lead to an interesting experiment. I used convert to -resample a set of images to 300dpi and redid the compile. They are all now too bod, many off the right side of the page. Then did the same but set to 72. They are still too big. Odd, from too small to too big.

I will try and be a bit more precise and craft a text doc to play with this and report the results.

Thanks for your help!

Guy

On 11/21/2012 10:51 AM, Sietse Brouwer wrote:
On Wed, Nov 21, 2012 at 3:55 PM, Guy Stalnaker <jstal...@wisc.edu> wrote:
Thanks - see my first post for a link to a web folder where you can find the 
.tex file, the .pdf context produces, two screenshots of the differing image 
treatment and two of the image files shown in the screenshots.

Gah --- missed that. Thanks!

The resolution of the image is is either not correctly set, or not
correctly read by ConTeXt --- so ConTeXt assumes 300dpi instead of 72.
I've attached a self-made image of 547px wide, and run the following
file:

\starttext
\externalfigure[CMSLogin.jpg] \crlf
\figurenaturalwidth\ -- \figurexresolution\ -- \figurexsize

\externalfigure[cross.jpg] \crlf
\figurenaturalwidth\ -- \figurexresolution\ -- \figurexsize
\stoptext

This prints the following dimensions for your figure and the Gimp-made
one, respectively:

8635829sp – 0 – 547
35982623sp – 72 – 547

Can't remember how to convert scaled points to inches, so here's some
fraction juggling instead.
The naturalwidth of the cross is 4.2 times larger:
35982623 / 8635829
= 4.166667

So the login jpg will have 4.16666666 times as many dpi.
72 * 4.166667
= 300 dpi

Which corresponds to this observation by you:

But note that I attempted to test the dpi theory by
selecting an image and using GIMP to set its
dpi to 300 yet that resulted in no visible change.

What if you use the GIMP to set its dpi to 72?

--Sietse


--

"There is only love, and then oblivion. Love is all we have
to set against hatred." (paraphrased) Ian McEwan

Guy Stalnaker, I^2@DOIT, 1210 West Dayton Street, Room 3209 CSS, Madison
WI 53719-1220, jstal...@wisc.edu, work 608.263.8035, cell 608.235.4718,
fax 608.265.6681,
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