[NTG-context] Wrong image size evaluation

[Taco Hoekwater]

nico wrote:
> Hello,
> 
> I have some troubles with a PNG image, that is not correctly rendered by  
> context (too small). The difference I've found with another correctly  
> displayed image is that the file does not contain any resolution unit (but  
> a pixels/inch default seems reasonable).

But pixels/cm is equally reasonable, and that is why pdftex ignores
invalid settings in PNG images completely, and uses its internal
default instead. You can control that default resolution by setting 
\pdfimageresolution to an appropriate guess:

   {\pdfimageresolution=72 \externalfigure[ch01dia1.png]}

Cheers, Taco