OpenCV绘图轮廓错误断言失败

Question

所以我正在尝试按照 https://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/ 中有关如何扫描文档的指南进行操作恰好在我应该找到轮廓并将其绘制到图像的第 2 步过程中，我在 drawContour 函数

上遇到 "Assertion Failed" 错误

导游没有

screenCnt = None

所以一开始我得到的错误是 screenCnt 不存在

在我添加它之后，却得到了 Assertion Failed 尽管我使用了与指南相同的图片并尝试了另一张图片

#find contour
cnts = cv2.findContours(edged.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
cnts = imutils.grab_contours(cnts)
cnts = cnts[0] if imutils.is_cv2() else cnts[1]
cnts = sorted(cnts, key=cv2.contourArea, reverse=True)[:5]
screenCnt = None

# loop over the contours
for c in cnts:
    peri = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.02 * peri, True)
    if len(approx) == 4:
        screenCnt = approx
        break

#draw contour
cv2.drawContours(image, [screenCnt], -1, (0, 255, 0), 2)

这是我得到的：

Traceback (most recent call last): File "C:/Users/User/PycharmProjects/learn/project/app.py", line 218, in cv2.drawContours(image, [screenCnt], -1, (0, 255, 0), 2)

cv2.error: OpenCV(4.1.0) C:\projects\opencv-python\opencv\modules\imgproc\src\drawing.cpp:2606: error: (-215:Assertion failed) reader.ptr != NULL in function 'cvDrawContours'

有什么解决办法吗？之前感谢

Answer 1

尝试打印您提供的函数的所有输入。我想你可能会发现不对劲。在下面的评论中让我知道。

Answer 2

尝试替换 screenCnt = 0 而不是 None。让我知道。供您参考，我提供了一小段代码：

(cnts, contours, heirarchy) = cv2.findContours(edged.copy(), 
cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)

cnts = contours[0]
screenCnt = 0

for contour in contours:
    # get rectangle bounding contour
    [x,y,w,h] = cv2.boundingRect(contour)

# draw rectangle around contour on original image
#cv2.rectangle(image,(x,y),(x+w,y+h),(255,0,255),2)

##### code added..for thresholding
for c in cnts:
    # approximate the contour
    peri = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.02 * peri, True)

    # if our approximated contour has four points, then
    # we can assume that we have found our screen
    if len(approx) == 4:
        screenCnt = approx
        break

OpenCV绘图轮廓错误断言失败

OpenCV Drawing Contour Error Assertion Failed

python

opencv

contour

opencv-drawcontour

cv2