Creating an array of images in python \ openCV \ numpy

Question

I'm trying to implement an "LOG blob detector" using python and openCV. the idea is to create 10-15 levels of LOG filters, apply each of them to my original gray scale image and save the images in an array of size height x width x numOfLevels and then find the local maximums on the 3D array.

The problem is I'm not sure how to save these in an array.

I tried to do the following:

myImage = cv2.imread('butterfly.jpg')
gray_image = cv2.cvtColor(myImage, cv2.COLOR_BGR2GRAY)
sigma = 2
k = 2**(0.25)
std2 = float(sigma**2)
arr = []
for i in range(10):
    filt_size =  2*np.ceil(3*sigma)+1
    H = log_filt( filt_size, sigma)
    H *= sigma**2
    dst = cv2.filter2D(gray_image,-1,H)
    arr.append(dst)
    cv2.imshow('Gray', dst)
    cv2.waitKey(0)
    cv2.destroyAllWindows()
    sigma = sigma * k
    std2 = float(sigma**2)
    plt.imshow(H,interpolation='nearest')

But then if I try to take on the of the images and use cv2.imshow(arr[0]) I get the following error:

TypeError: Required argument 'mat' (pos 2) not found

What am I doing wrong here?

Is there a better way to save these in an array?

Maybe using np.array somehow?

Please always include the full error traceback, not just the error message. — cel
– cel, Commented Nov 7, 2015 at 16:18

agold · Accepted Answer · 2015-11-07 19:11:10Z

3

Your error:

cv2.imshow(arr[0]) I get the following error: TypeError: Required argument 'mat' (pos 2) not found

Is because you pass the image (arr[0]) as first parameter, but you should pass it as second:

cv2.imshow('WindowName', arr[0])

See the OpenCV 2.4 and 3.0 documentation of imshow:

cv2.imshow(winname, mat)

answered Nov 7, 2015 at 19:11

agold

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