Reputation: 359
Updating RGB image values given a list of indexes
l have an image of (240,320,3)
l would like to set some values to [255,0,0].
l give the indexes as follow:
indexes
[array([0, 0]),
array([0, 1]),
array([0, 2]),
array([0, 3]),
array([0, 4]),
array([0, 5]),
array([0, 6]),
array([0, 7]),
array([0, 8]),
array([0, 9]),
array([ 0, 10]),
array([ 0, 11]),
array([ 0, 12]),
array([ 0, 13]),
array([ 0, 14]),
array([ 0, 15]),
array([ 0, 16]),
array([ 0, 17]),
array([ 0, 18]),
array([ 0, 19]),
array([ 0, 20]),
array([ 0, 21]),
array([ 0, 22]),
array([ 0, 23]),
array([ 0, 24]),
array([ 0, 25]),
array([ 0, 26]),
array([ 0, 27]),
array([ 0, 28]),
array([ 0, 29]),
array([ 0, 30]),
array([ 0, 31]),
array([ 0, 32]),
array([ 0, 33]),
array([ 0, 34]),
array([ 0, 35]),
array([ 0, 36]),
array([ 0, 37]),
array([1, 0]),
array([1, 1]),
array([1, 2]),
array([1, 3]),
array([1, 4]),
array([1, 5]),
array([1, 6]),
array([1, 7]),
array([1, 8]),
array([1, 9]),
array([ 1, 10]),
array([ 1, 11]),
array([ 1, 12]),
array([ 1, 13]),
array([ 1, 14]),
array([ 1, 15]),
array([ 1, 16]),
array([ 1, 17]),
array([ 1, 18]),
array([ 1, 19]),
array([ 1, 20]),
array([ 1, 21]),
array([ 1, 22]),
array([ 1, 23]),
array([ 1, 24]),
array([ 1, 25]),
array([ 1, 26]),
array([ 1, 27]),
array([ 1, 28]),
array([13, 34]),
array([13, 35]),
array([13, 36]),
array([13, 37]),
array([14, 0]),
array([14, 1]),
array([14, 2]),
array([14, 3]),
array([14, 4]),
array([14, 5]),
array([14, 6]),
array([14, 7]),
array([14, 8]),
array([14, 9]),
array([14, 10]),
array([14, 11]),
array([14, 12]),
array([14, 13]),
array([14, 14]),
array([14, 15]),
array([14, 16]),
array([14, 17]),
array([14, 18]),
array([14, 19]),
array([14, 20]),
array([14, 21]),
array([14, 22]),
array([14, 23]),
array([14, 24]),
array([14, 25]),
array([14, 26]),
array([14, 27]),
array([14, 28]),
array([14, 29]),
array([14, 30]),
array([14, 31]),
array([14, 32]),
array([14, 33]),
array([14, 34]),
array([14, 35]),
array([14, 36]),
array([14, 37]),
array([15, 0]),
array([15, 1]),
array([15, 2]),
array([15, 3]),
array([15, 4]),
array([15, 5]),
array([16, 13]),
array([16, 14]),
array([16, 15]),
array([16, 16]),
array([16, 17]),
array([16, 18]),
array([16, 19]),
array([17, 24]),
array([17, 25]),
array([17, 26]),
array([17, 27]),
array([17, 28]),
array([17, 29]),
array([17, 30]),
array([17, 31]),
array([17, 32]),
array([18, 0]),
array([18, 1]),
array([22, 18]),
array([22, 19]),
array([22, 20]),
array([22, 21]),
array([22, 22]),
array([22, 23]),
array([22, 24]),
array([22, 25]),
array([22, 26]),
array([22, 27]),
array([22, 28]),
array([22, 29]),
array([22, 30]),
array([22, 31]),
array([22, 32]),
array([22, 33]),
array([22, 34]),
array([22, 35]),
array([22, 36]),
array([22, 37]),
array([22, 38]),
array([22, 39]),
array([22, 40]),
array([22, 41]),
array([22, 42]),
array([22, 43]),
array([22, 44]),
array([22, 45]),
array([22, 46]),
array([26, 1]),
...]
Now l load the image
from PIL import Image
img=Image.open(image)
img=np.array(img)
Given the list of indexes, l would like to set img[indexes]=[255,0,0]
What is wrong with img[indexes]=[255,0,0] ?
It doesn't seem to do the job :
img[indexes[0]] where indexes[0]=[0,0]
returns a an array of arrays, however l'm supposed to get the RGB vector at index (0,0).
Than l tried img[[0,0]] l got the same result.
It means that img[[0,0]]==img[indexes[0]] returns an array of arrays rather than the RGB vector at the index (0,0)
However, img[indexes[0,0],indexes[0,1]] returns the correct RGB vector.
My question
How can l pass a list of indexes to my image to update the values at the given indexes as follow;
img[indexes]=[255,0,0]
Thank you
EDIT 1 img[index[0]] returns
array([[[0, 0, 0],
[0, 0, 0],
[0, 0, 0],
...,
[0, 0, 0],
[0, 0, 0],
[0, 0, 0]],
[[0, 0, 0],
[0, 0, 0],
[0, 0, 0],
...,
[0, 0, 0],
[0, 0, 0],
[0, 0, 0]]], dtype=uint8)
where l'm supposed to get an RGB vector [223,15,78] corresponding to index(0,0)
and img[indexes] retruns
array([[[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]],
[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]]],
[[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]],
[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]]],
[[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]],
[[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0],
...,
[ 0, 0, 0],
[ 0, 0, 0],
[ 0, 0, 0]]],
...,
[[[ 0, 0, 2],
[ 0, 0, 2],
[ 0, 0, 2],
...,
[ 0, 2, 0],
[ 0, 2, 0],
[ 0, 2, 0]],
[[108, 106, 93],
[108, 106, 93],
[109, 105, 93],
...,
[170, 165, 143],
[177, 175, 150],
[173, 171, 146]]],
[[[ 0, 0, 2],
[ 0, 0, 2],
[ 0, 0, 2],
...,
[ 0, 2, 0],
[ 0, 2, 0],
[ 0, 2, 0]],
[[129, 127, 114],
[129, 127, 114],
[130, 126, 114],
...,
[155, 150, 128],
[164, 164, 138],
[172, 172, 146]]],
[[[ 0, 0, 2],
[ 0, 0, 2],
[ 0, 0, 2],
...,
[ 0, 2, 0],
[ 0, 2, 0],
[ 0, 2, 0]],
[[150, 133, 126],
[149, 132, 125],
[147, 130, 123],
...,
[162, 135, 124],
[179, 152, 143],
[184, 157, 148]]]], dtype=uint8)
image sample :
img[140:200]
array([[[159, 146, 114],
[115, 100, 71],
[ 90, 73, 45],
...,
[245, 187, 183],
[252, 197, 194],
[253, 198, 195]],
[[206, 193, 159],
[164, 149, 118],
[119, 102, 72],
...,
[243, 188, 185],
[246, 192, 190],
[251, 197, 195]],
[[195, 182, 148],
[182, 167, 134],
[150, 134, 101],
...,
[241, 185, 184],
[245, 191, 189],
[251, 200, 197]],
...,
[[251, 234, 244],
[251, 234, 244],
[251, 234, 244],
...,
[104, 77, 70],
[102, 75, 68],
[102, 75, 68]],
[[251, 234, 244],
[251, 234, 244],
[251, 234, 244],
...,
[ 94, 69, 62],
[ 91, 66, 59],
[ 89, 64, 57]],
[[251, 234, 244],
[251, 234, 244],
[251, 234, 244],
...,
[ 85, 62, 56],
[ 81, 58, 52],
[ 78, 58, 51]]], dtype=uint8)
Upvotes: 1
Views: 239
Answers (1)
Reputation: 1599
I believe the problem you're running into is advanced indexing vs simple indexing, as described within the numpy documentation.
given a dummy img array of shape (240,320,3), we have something like this:
img = np.random.randint(1,255, (240,320,3))
print img
array([[[ 25, 160, 160],
[238, 222, 252],
[ 7, 73, 81],
...,
[144, 198, 83],
[186, 204, 150],
[249, 234, 105]],
[[ 52, 242, 214],
[230, 139, 165],
[ 95, 69, 168],
...,
[ 40, 226, 111],
[190, 114, 165],
[235, 189, 108]],
[[146, 245, 22],
[ 88, 156, 27],
[120, 112, 13],
...,
[220, 31, 119],
[ 67, 117, 65],
[108, 145, 196]],
...,
If we want to access the first element in the first nested array ([25, 160, 160]), we would call it with simple indexing:
print img[0,0] # array([ 25, 160, 160])
However, when you pass in an index array, numpy interprets the indexing as advanced: img[[0,0]] return img[0] twice!; img[[0,0,0]] returns img[0] three times! This is why you're seeing oddly shaped arrays when you call img[indexes].
To achieve the desired result of updating img values to [255,0,0] as indicated in your indexes list, you need to first convert each index within indexes to a tuple; this will signal to numpy to interpret your arrays as simple indexing:
an_index = np.array([0,0])
( img[0,0] == img[tuple(an_index)] ).all() # True
To convert your indexes to tuples, you can use map:
indexes = np.random.randint(0,10,(100,2))
index_of_tuples = map(tuple, indexes)
img[index_of_tuples] = [255,0,0]
Now, value of img will be updated to [255,0,0], as indicated within your original indexes.
Upvotes: 1
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