CODEWITHSUNDEEP
pythonopencv
Max
Max

Reputation: 105

Sum array in Python

I am trying to sum up the greyscale pixel values of a greyscale image "1.jpg" for each vertical columns of pixels in the image.

Here is the code:

import cv2
img = cv2.imread("1.jpg", 0)
for i in range (img.shape[0]):
        aaa = img[i]
        print aaa

Doing this i get something like

aaa = [1,2,3] [2,3,4] [3,4,5] [4,5,6] .....

Now how do I sum up the array to get:

bbb = [6, 9, 12, 15, ....]

If I do:

import cv2
img = cv2.imread("1.jpg", 0)
for i in range (img.shape[0]):
        aaa = img[i]
        bbb = sum(aaa, 0)
        print bbb

I get:

6
9
12
15
.
..
...

but thats not what I need !!!

UPDATE : Solved

Was finally able to do it by this:

import cv2
bbb = []
img = cv2.imread("1.jpg", 0)
for i in range (img.shape[0]):
        bbb.append(sum(img[i]))

Upvotes: 0

Views: 3239

Answers (4)

P.Madhukar
P.Madhukar

Reputation: 464

If you get array like :

[1,2,3]
[2,3,4]
[3,4,5] 
[4,5,6]

then to sum up the array and to store it into a different list, try this code:

import cv2

img = cv2.imread("1.jpg", 0)
final_list = []
for i in range (img.shape[0]):
    final_list.append(reduce(lambda x,y: x+y, img[i]))
print final_list

Upvotes: 0

Giridhur
Giridhur

Reputation: 174

Fastest way among all answers perhaps, try using the numpy package side by side. as follows :

import cv2
import numpy as np
img = cv2.imread('your_image_file')
sum_cols = np.sum(img,axis=1)
sum_cols = np.sum(img,axis=1) #if the image is a color image.

This works, and sums along the second axis, ie the column sum for each row and each color channel.

Upvotes: 1

101
101

Reputation: 8999

This should do it (untested). Note that img.shape[1] gives the number of image columns. 

import cv2
results = []
img = cv2.imread('1.jpg', cv2.IMREAD_GRAYSCALE)
for col in range(img.shape[1]):
    results.append(sum(img[col]))

Upvotes: 0

宏杰李
宏杰李

Reputation: 12168

you should put aaa in a container, like a list or set
aaa = []
for i in range (img.shape[0]):
        aaa.append(img[i])
        print aaa

or 

aaa = [ i for i in range (img.shape[0])]


aaa = [[1,2,3],[2,3,4],[3,4,5],[4,5,6]]
[sum(a)for a in aaa]

out:

[6, 9, 12, 15]

Upvotes: 0

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