Python Forum

Hi,
I have a problem with my array list in pyhton while using cv2.
I have an array list that looks like that:
A=[[[RGB],[RGB]],....,[[RGB],[RGB]]]
A[i] = heigh of the image
A[][j] = the lenght of the picture
I need to shorten the heigh and the lenght of A,
to do so
A=A[a:b] (with [a,b] the only portion i need)
and i'd like to do :

for i in range(len(A)):
     A[i]=A[i][c:d] #(to shorten each A[i] the portion i need)

but it doesn't work as it doesn't do what i'd suppose it'd do... is there is a way to remove those unwanted part ? (because del and remove doesn't work as for del, it's an array and it doesn't like it, and for remove i don't know what color is in that pixel so i can't remove the specific pixel i don't want...

Yuky

How is it not working? It looks good to me. I made my own version:

x = [[1, 2, 3], [1, 2, 3], [1, 2, 3]]

for index in range(len(x)):
    x[index] = x[index][:2]
x = x[:2]

print(x)

Which prints [[1, 2], [1, 2]]. However, you generally want to iterate directly over the list instead of it's indexes, so I would do something like this:

y = [[1, 2, 3], [1, 2, 3], [1, 2, 3]]

z = []
for row in y[:2]:
    z.append(row[:2])
y = z

print(z)

Which has the same result.

Traceback (most recent call last):
File "<console>", line 1, in <module>
File "C:\Users\User\Desktop\CPGE\Test Recadrage.py", line 98, in recadrer
frame[i]=frame[i][d[l]:b[l]]
ValueError: could not broadcast input array from shape (1310,3) into shape (1920,3)

import cv2
cap = cv2.VideoCapture('185012.mov')
frame = cap.read()[1]
frame=frame[c[l]:a[l]]
for i in range(len(frame)): 
    frame[i]=frame[i][d[l]:b[l]]

That's the error it shows me...

So it's not a standard Python list. Is cv2 using numpy arrays, or does it have it's own arrays? I would look into the documentation for whatever array type it is. Also, my preferred method above of building a new list might get around the reshaping issue.

yeah it's an array, it works as
A[a:b,c:d]
thanks for your help :)