Finding whether the lines in the image are straight (linear) or curved

Question

I have the following image, this image takes values between 0 and 9. Our matrix size is a 512*512 matrix. Here, my aim is to look at this matrix and I want to find out whether the lines in the image are straight (linear) or curved. I added an image as an example, but I don't know how to do it. i need help on this.

This is my matrix : https://drive.google.com/file/d/14h0OD316tMNP-JKhTP4xpFI9Y293-5QN/view?usp=sharing

To read this array you have to use :

with open('test.npy', 'rb') as f:
    a = np.load(f)
print(a)