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When reading an image for RGB pixel values ​​there is a different green value in matlab and python

I want to get pixel values ​​for RGB from image. I did it in Matlab and Python, but I got different values, especially on the green value. I would be grateful if you have any advice on this matter. thanks Here is my code in python

from PIL import Image
import numpy as np

im = Image.open("lena.jpg")
imPixelVal = np.ones(np.size(im))
imSize = np.size(im)

for i in range (0,imSize[0]):
            for j in range (0,imSize[1]):         
                ij = i , j
                p = im.getpixel(ij)
                imPixelVal[i,j] = (0.2989 * p[0]) + (0.5870 * p[1]) + (0.1140 * p[2])
                print p[0]
                print p[1] 
                print p[2]

Also this is the code in Matlab:

Im=imread('lena.jpg');
Img = (ones(size(Im,1),size(Im,2))); 

for i=1:size(Im,1)
      for j=1:size(Im,2)
          Img(i,j)=0.2989*Im(i,j,1)+0.5870*Im(i,j,2)+0.1140*Im(i,j,3);
      end
end
Im(1,1,1)
Im(1,1,2)
Im(1,1,3)
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1 answer


It looks like images are read in a different "direction" in Python compared to Matlab.
If you change your python code to:

ij = j , i

instead

ij = i , j

you will get the same result as in Matlab.



If you want to Matlab gave the same results as the Python, you'll have to turn i

and j

there:

Img(j,i)=0.2989*Im(j,i,1)+0.5870*Im(j,i,2)+0.1140*Im(j,i,3);


This is how I figured it out through simple debugging:

  • I first got the image here and saved it as .jpg

    .

  • Then I changed the Matlab loops to

    for i=1:2
    for j=1:2

    So, I would get the first 4 pixels.

  • Print to i

    , j

    and the contents Im

    , I got:

    i = 1, j = 1
225, 137, 125

i = 1, j = 2
227, 139, 127

i = 2, j = 1
224, 136, 124

i = 2, j = 2
226, 138, 126

  • Now I have done the same in python:

    for i in range (0,2):
    for j in range (0,2):

  • This gave me:

    (0, 0)
225 137 125
(0, 1)
224 136 124
(1, 0)
227 139 127
(1, 1)
226 138 126

  • This showed me that the order is different from Matlab and Python.

  • Hence, changing i

    and j

    in Python from ij = i, j

    to ij = j, i

    will reproduce the Matlab results.
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