Something terrible must be done to png pictures, either in ConTeXt or in luatex.
I have the following minimal sample code and picture. I include the png for those who want to check.
% Test png addition.
\starttext
Place png figure.\par
\placefigure{Test figure}{\externalfigure[test.png]}
\stoptext
Without the png-picture it makes an 8KB pdf.
But with the png-picture the pdf swells to 1.8MB.
And that for a png-picture of only 48KB.
Moreover making a zip of all this stuff brought the size back to 110KB.In the log:
ConTeXt ver: 2011.11.04 14:15 MKIV fmt: 2011.11.10 int: english/english
mkiv lua stats > graphics processing time - 0.001 seconds including tex, 1 processed images
What is done with the png and can it be remedied?
This swelling up of small picture to such enormous proportions makes the inclusion of png-picture nearly impossible, at least impractable.