No features detected in still image

[emillundh]

Hi, this is probably not a bug but I wonder if you can help me with this.
Why do I not detect any features in a still image that's in an <img> tag on my html page?
I basically copied the fast_corners demo. Here's the core code:
http://pastebin.com/Pfx2Hqz9
Tried with the other feature detectors as well. Tried several threshold values down to 1. Tried with several jpg and png images. Checked that the array img_u8 does contain nonzero, nonconstant, data. Tried to do equalize_histogram before detect.
None of it helps. 0 is the output from fast_corners.detect.
Do you have any idea what I did wrong?