javascript - 围绕对象opencv.js的边界矩形在控制台中抛出错误

Question

我正在使用 opencv.js 库从图像中查找对象。无法在资助对象周围绘制矩形

我已经尝试过以下代码块

        var canvas = document.getElementById('canvasInput');
        canvas.renderImage(e.target.files[0]);
        let src = cv.imread("canvasInput");
        let dst = cv.Mat.zeros(src.rows, src.cols, cv.CV_8UC3);
        cv.cvtColor(src, src, cv.COLOR_RGBA2GRAY, 0);
        cv.threshold(src, src, 177, 200, cv.THRESH_BINARY);
        let contours = new cv.MatVector();
        let hierarchy = new cv.Mat();
        cv.findContours(src, contours, hierarchy, cv.RETR_CCOMP, cv.CHAIN_APPROX_SIMPLE);
        let cnt = contours.get(0);
        let rect = cv.boundingRect(cnt);
        let contoursColor = new cv.Scalar(255, 255, 255);
        let rectangleColor = new cv.Scalar(255, 0, 0);
        cv.drawContours(dst, contours, 0, contoursColor, 1, 8, hierarchy, 100);
        let point1 = new cv.Point(rect.x, rect.y);
        let point2 = new cv.Point(rect.x + rect.width, rect.y + rect.height);
        cv.rectangle(dst, point1, point2, rectangleColor, 2, cv.LINE_AA, 0);
        cv.imshow('canvasOutput', dst);
        src.delete(); dst.delete(); contours.delete(); hierarchy.delete(); 
         cnt.delete();

但发现

opcv.js:21 未捕获类型错误:无法读取未定义的属性“$$”
在 RegisteredPointer.nonConstNoSmartPtrRawPointerToWireType [as toWireType] (opcv.js:21)
在 Object.boundingRect (eval at new_ (opcv.js:21), :7:26)
在 HTMLInputElement.inputElement.addEventListener (openCv.php:52)
nonConstNoSmartPtrRawPointerToWireType @ opcv.js:21
boundingRect@VM24025:7

inputElement.addEventListener@openCv.php:52

控制台中的错误。

Answer 1

当 findContours 时将引发此错误。产值contours有 0 个元素，因此取消引用空指针。