OpenCV 4.1.0版drawContours

2022-01-09 00:00:00 python opencv computer-vision image-processing image

问题描述

我的以下代码在 OpenCV 3.4.1 上运行良好，但现在不适用于 OpenCV 4.1.0 并出现错误.我不知道如何使代码适应较新的版本，你能帮我吗?非常感谢

I have the following code that worked well with OpenCV 3.4.1 and now is not working with OpenCV 4.1.0 and gives an error. I do not know how to adapt the code with the newer version, can you help me with that? Thanks a lot

def ImageProcessing(image):
    image = cv2.absdiff(image, background)
    h, gray = cv2.threshold(image, 65, 255, cv2.THRESH_BINARY_INV);
    gray = cv2.medianBlur(gray,5)

    kernel = np.ones((3,3), np.uint8)

    gray = cv2.erode(gray, kernel, iterations=1)#1

    des = cv2.bitwise_not(gray)
    tmp = cv2.findContours(des,cv2.RETR_CCOMP,cv2.CHAIN_APPROX_SIMPLE)
    contour, hier = tmp[1], tmp[0]

    for cnt in contour:
        cv2.drawContours(des,[cnt],0,255,-1)

    gray = cv2.bitwise_not(des)

    gray = cv2.dilate(gray, kernel, iterations=1)#1

    return gray

错误是

cv2.error: OpenCV(4.1.0)/io/opencv/modules/imgproc/src/drawing.cpp:2509: 错误: (-215:Assertion failed) npoints > 0 in function 'drawContours'

cv2.error: OpenCV(4.1.0) /io/opencv/modules/imgproc/src/drawing.cpp:2509: error: (-215:Assertion failed) npoints > 0 in function 'drawContours'

解决方案

根据 OpenCV 版本，cv2.findContours() 有不同的返回签名.

Depending on the OpenCV version, cv2.findContours() has varying return signatures.

在 OpenCV 3.4.X 中，cv2.findContours() 返回 3 个项目

In OpenCV 3.4.X, cv2.findContours() returns 3 items

image, contours, hierarchy = cv.findContours(image, mode, method[, contours[, hierarchy[, offset]]])

在 OpenCV 4.1.X 中，cv2.findContours() 返回 2 项

In OpenCV 4.1.X, cv2.findContours() returns 2 items

contours, hierarchy = cv.findContours(image, mode, method[, contours[, hierarchy[, offset]]])

无论版本如何，您都可以轻松获取轮廓:

You can easily obtain the contours regardless of the version like this:

tmp = cv2.findContours(des,cv2.RETR_CCOMP,cv2.CHAIN_APPROX_SIMPLE)
contours = tmp[0] if len(tmp) == 2 else tmp[1]

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