零分区错误（Python）

Question

我得到了一些图像的零除法错误（尽管很多图像工作得很好）：

代码如下：

image = skimage.io.imread('test.png', False)
image_gray = skimage.io.imread('test.png', True)
blurred = cv2.GaussianBlur(img_as_ubyte(image_gray), (5, 5), 0)
thresh = threshold_li(blurred)
binary = blurred > thresh
binary_cv2 = img_as_ubyte(binary)

# find contours in the thresholded image
cnts = cv2.findContours(binary_cv2.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
cnts = cnts[0] if imutils.is_cv2() else cnts[1]

# loop over the contours
for c in cnts:
    # compute the center of the contour
    M = cv2.moments(c)
    cX = int(M["m10"] / M["m00"])
    cY = int(M["m01"] / M["m00"])

    # draw the contour and center of the shape on the image
    cv2.drawContours(img_as_ubyte(image), [c], -1, (0, 255, 0), 2)
    cv2.circle(img_as_ubyte(image), (cX, cY), 7, (255, 255, 255), -1)
    cv2.putText(img_as_ubyte(image), "center", (cX - 20, cY - 20),
    cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 255, 255), 2)

viewer = ImageViewer(image)
viewer.show()

---

Traceback (most recent call last):
  File "Center.py", line 26, in <module>
    cX = int(M["m10"] / M["m00"])
ZeroDivisionError: float division by zero

提前谢谢！

Answer 1

错误是不言而喻的。你不能把一个数字除以零。如果M["m00"]为零，则需要适当地处理它。检查M["m00"]中的0值。

if M["m00"] != 0:
    cX = int(M["m10"] / M["m00"])
    cY = int(M["m01"] / M["m00"])
else:
    # set values as what you need in the situation
    cX, cY = 0, 0

Answer 2

计算质心，例如：

cx = 0
cy = 0
for p in contour:
    cx += p[0][0]
    cy += p[0][1]
cx = int(cx/len(contour))
cy = int(cy/len(contour))

或者看看boundingRect()（3.4.3）。

相关：Finding the center of a contour using opencv and visual c++

Answer 3

可能你的轮廓不好

Note Since the contour moments are computed using Green formula, you may get seemingly odd results for contours with self-intersections, e.g. a zero area (m00) for butterfly-shaped contours.