OpenCV 的 matchShapes 总是返回 0

Question

我正在使用 matchShapes 来识别一些基本轮廓。但是，无论我比较什么轮廓，它都会返回 0...

模板图片:

示例输入图像:

代码:

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()，然后是findContours()，最后是this->轮廓 = 轮廓 [0]).

结果输出(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(因此轮廓不同)，但 match == 0 总是。这是怎么回事？

编辑:OpenCV 版本为 2.4.9(昨天克隆和构建)。

Answer 1

此问题与 OpenCV 2.4.9 中的错误有关。

在 2.4.5(稳定版)上运行良好。

参见 this post on OpenCV Answers .