Revision history [back]

Try the niBlackThreshold

ximgproc::niBlackThreshold( im, thresh, 255, THRESH_BINARY_INV, 21, -1.0 );

That gives me images something like this:

Not perfect, but you said you have hand contours, so you can drop everything outside of that, then filter the inner blobs by shape and intensity. The false alarms will still be white. Or do template matching on each one to see how closely it matches, and only keep the good ones. Lots of ways to remove false alarms, if you get good, distinct, blobs.