Clone a NumPy array multiple times… here is a solution to the problem.
Clone a NumPy array multiple times
I load a picture into a numpy array and need to threshold the picture at 2 different thresholds.
import numpy as np
import cv2
cap = cv2. Videocapture(0)
_,pic = cap.read()
pic1 = pic
pic2 = pic
pic1[pic1 > 100] = 255
pic2[pic2 > 200] = 255
When I only want them to modify pic1 and pic2, this code will always edit pic
Solution
In Python, there is a difference between objects and variables. A variable is a name assigned to an object; And an object can have multiple names in memory.
Via pic1 = pic; pic2 = pic
, you assign the same object to several different variable names, so you end up modifying the same object.
What you want is to create a copy using np.ndarray.copy
pic1 = pic.copy()
pic2 = pic.copy()
Or, very similarly, use np.copy
—
pic1, pic2 = map(np.copy, (pic, pic))
This syntax actually makes it really easy to clone pic
as many times :
pic1, pic2, ... picN = map(np.copy, [pic] * N)
where N
is the number of replicas you want to create.