cvMinMaxLoc

[GoogleCodeExporter]

cvMinMaxLoc in C use as parameter 4 pointers, but converting the C code:

CvPoint    minloc, maxloc;
double    minval, maxval;
cvMinMaxLoc(res, &minval, &maxval, &minloc, &maxloc, 0);

into java:
CvPoint minloc = new CvPoint();
CvPoint maxloc = new CvPoint();
double[] minval = {};
double[] maxval = {};
cvMinMaxLoc(res, minval, maxval, minloc, maxloc, null);

throws a untraceable fatal error, im doing something bad in this function call?

after calling cvMinMaxLoc i use
cvMatchTemplate(img, tpl, res, CV_TM_SQDIFF);
without error.

Original issue reported on code.google.com by graficag...@gmail.com on 5 Mar 2011 at 1:22

[GoogleCodeExporter]

Yes, your minval and maxval have length 0. If you want to get something in 
return, they need to be at least of length 1, if not, pass null. I guess I 
should pass a NULL pointer there when the user provides something like that..

Original comment by samuel.a...@gmail.com on 5 Mar 2011 at 1:31

• Changed state: Started

[GoogleCodeExporter]

thanks for the answer, but i can´t make cvMatchTemplate + cvMinMaxLoc work, 
"translating" from C examples doesnt seem to work, someone has run these OpenCV 
functions and has an example for me to try?

Original comment by graficag...@gmail.com on 10 Mar 2011 at 4:02

[GoogleCodeExporter]

Can you post the code you "translated" that "doesn't seem to work"?

Original comment by samuel.a...@gmail.com on 10 Mar 2011 at 6:29

[GoogleCodeExporter]

Sorry Samuel, i had deleted the previous code, so I started from scratch and 
now it works perfectly.

this issue is resolved

Original comment by graficag...@gmail.com on 12 Mar 2011 at 8:48

[GoogleCodeExporter]

Apparently, some versions of C/C++ do support pointers of size zero:

The pointer returned points to the start (lowest byte address) of the allocated 
space. If the space cannot be allocated, a null pointer is returned. If the 
size of the space requested is zero, the behavior is implementation defined: 
either a null pointer is returned, or the behavior is as if the size were some 
nonzero value, except that the returned pointer shall not be used to access an 
object.
- http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf

So this is not a bug of JavaCPP or JavaCV after all :) Marking as invalid

Original comment by samuel.a...@gmail.com on 6 Apr 2011 at 1:16

• Changed state: Invalid