image dilation with python - python-3.x

Question

I'm trying to execute a piece of code I found online and it is giving me the following error.
I'm new to opencv so please help me.
error:
<ipython-input-1-7fe9c579ec14> in image_masking(filepath)
15 gray = cv2.imread(filepath,0)
16 edges = cv2.Canny(gray, CANNY_THRESH_1, CANNY_THRESH_2)
---> 17 edges = cv2.dilate(edges,None)
18 edges = cv2.erode(edges, None)
19
error: OpenCV(3.4.1) C:\Miniconda3\conda-bld\opencv-
suite_1533128839831\work\modules\core\src\matrix.cpp:760: error: (-215)
dims <= 2 && step[0] > 0 in function cv::Mat::locateROI
code:
import cv2
import numpy as np
def image_masking(filepath):
BLUR = 21
CANNY_THRESH_1 = 100
CANNY_THRESH_2 = 100
MASK_DILATE_ITER = 10
MASK_ERODE_ITER = 10
MASK_COLOR = (0.0,0.0,0.0) # In BGR format
gray = cv2.imread(filepath,0)
edges = cv2.Canny(gray, CANNY_THRESH_1, CANNY_THRESH_2)
edges = cv2.dilate(edges,None)
edges = cv2.erode(edges, None)
contour_info = []
_, contours, __ = cv2.findContours(edges, cv2.RETR_LIST, cv2.CHAIN_APPROX_NONE)
for c in contours:
contour_info.append((c, cv2.isContourConvex(c), cv2.contourArea(c),))
contour_info = sorted(contour_info, key=lambda c: c[2], reverse=True)
max_contour = contour_info[0]
for c in contour_info:
cv2.fillConvexPoly(mask, c[0], (255))
mask = cv2.dilate(mask, None, iterations=MASK_DILATE_ITER)
mask = cv2.erode(mask, None, iterations=MASK_ERODE_ITER)
mask = cv2.GaussianBlur(mask, (BLUR, BLUR), 0)
mask_stack = np.dstack([mask]*3)
mask_stack = mask_stack.astype('float32') / 255.0
img = img.astype('float32') / 255.0
masked = (mask_stack * img) + ((1-mask_stack) * MASK_COLOR)
masked = (masked * 255).astype('uint8')
fileName, fileExtension = filepath.split('.')
fileName += '-masked.'
filepath = fileName + fileExtension
print(filepath)
cv2.imwrite(filepath, masked)
if __name__ == '__main__':
filepath = 'C:\\Users\HP\Downloads\test3.jpg'
image_masking(filepath)
i tried replacing None in dilate function with kernel but it is giving me the same error

Answer 1

The second argument to cv2.dilate and cv2.erode should be the kernel with which you want to perform dilation/erosion as it is shown in the docs: opencv documentation
For example, you can try to do it like that:
kernel = np.ones((3, 3), np.uint8)
edges = cv2.dilate(edges, kernel)
edges = cv2.erode(edges, kernel)
Good luck with further opencv exploration!