# matchShapes always returns 0

I'm using `matchShapes`

to recognize some basic contours. However, it's returning 0, no matter what contours I compare...

Template images:

Examplary input image:

The code:

```
using std::vector;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
findContours(binary, contours, hierarchy,
CV_RETR_CCOMP, CV_CHAIN_APPROX_TC89_KCOS);
drawContours(binary, contours, -1, Scalar(255, 255, 255));
if (!contours.size()) // avoid sigsegv
return;
for (int idx = 0; idx >= 0; idx = hierarchy[idx][0]) {
double bestMatch = INFINITY;
int bestI = -1;
for (int i = 0; i < knownContours.size(); i++) {
vector<Point>& a = knownContours[i].contour;
vector<Point>& b = contours[idx];
std::cout << "a.size = " << a.size() << ", b.size = " << b.size() << std::endl;
double match = matchShapes(b, a, CV_CONTOURS_MATCH_I1, 0);
std::cout << "idx=" << idx << " ? " << knownContours[i].name << " = " << match << std::endl;
if (bestI == -1 || match < bestMatch) {
bestI = i;
bestMatch = match;
}
}
}
```

(`knownContours`

are obviously initialized with template image data: `imread()`

, then `findContours()`

, finally `this->contour = contours[0]`

).

And resulting output (a fragment):

```
-- new frame
a.size = 57, b.size = 74
idx=0 ? circle = 0
a.size = 80, b.size = 74
idx=0 ? cross = 0
a.size = 45, b.size = 74
idx=0 ? triangle = 0
a.size = 57, b.size = 60
idx=1 ? circle = 0
a.size = 80, b.size = 60
idx=1 ? cross = 0
a.size = 45, b.size = 60
idx=1 ? triangle = 0
-- new frame
a.size = 57, b.size = 75
idx=0 ? circle = 0
a.size = 80, b.size = 75
idx=0 ? cross = 0
a.size = 45, b.size = 75
idx=0 ? triangle = 0
a.size = 57, b.size = 57
idx=1 ? circle = 0
a.size = 80, b.size = 57
idx=1 ? cross = 0
a.size = 45, b.size = 57
idx=1 ? triangle = 0
-- new frame
a.size = 57, b.size = 76
idx=0 ? circle = 0
a.size = 80, b.size = 76
idx=0 ? cross = 0
a.size = 45, b.size = 76
idx=0 ? triangle = 0
a.size = 57, b.size = 51
idx=1 ? circle = 0
a.size = 80, b.size = 51
idx=1 ? cross = 0
a.size = 45, b.size = 51
idx=1 ? triangle = 0
```

So the sizes of compared contours differ (so the contours differ), yet `match == 0`

always. What's going on here?

** Edit:** OpenCV version is 2.4.9 (cloned & built yesterday).

trying to run your testcase on 2.4.9 - are you cheating with the flags here, or did you mix up 2.4.5 stuff (again) ?

CV_RETR_CCOMP vs. RETR_CCOMP, CV_CHAIN_APPROX_TC89_KCOS vs. CV_CHAIN_APPROX_TC89_KCOS

can't find any replacement for CV_CONTOURS_MATCH_I1 (that might be a bug,btw), using 1 instead. what's there on your side ?

besides that, similar results(match==0)

diving in, the hu-moments are all 0 already.