我matchShapes用来识别一些基本轮廓。但是，无论我比较什么轮廓，它都返回 0...
模板图片：
示例输入图像：
编码：
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显然是用模板图像数据初始化的：imread()，然后findContours()，最后this->contour = contours[0]）。
结果输出（一个片段）：
-- 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
所以比较轮廓的大小不同（所以轮廓不同），但match == 0总是如此。这里发生了什么？
编辑： OpenCV 版本是 2.4.9（昨天克隆和构建）。