使用OpenCV.js进行投影变换时，为什么会出现空白透明图片？

// ... (其他代码，例如图像加载和轮廓检测) ...

if (approx.total() === 4) {
    let points = [];
    const data32s = approx.data32s;
    for (let i = 0, len = data32s.length / 2; i < len; i++) {
        points[i] = { x: data32s[i * 2], y: data32s[i * 2 + 1] };
    }
    console.log("Detected quadrilateral points:", points);

    try {
        let srcquad = cv.matFromArray(4, 1, cv.CV_32FC2, points.flat());
        let dstquad = cv.matFromArray(4, 1, cv.CV_32FC2, [0, 0, img.cols, 0, img.cols, img.rows, 0, img.rows]);
        let transmtx = cv.getPerspectiveTransform(srcquad, dstquad);
        if (!transmtx) {
            throw new Error("Failed to compute perspective transform.");
        }
        let target = new cv.Mat();
        cv.warpPerspective(img, target, transmtx, new cv.Size(img.cols, img.rows));
        cv.imshow('canvasoutput', target);

        srcquad.delete();
        dstquad.delete();
        transmtx.delete();
        target.delete();

    } catch (error) {
        console.error("Error during perspective transform:", error);
    }
}

// ... (其他代码，例如内存释放) ...
img.delete(); //释放原始图像