J. Castro - 7 months ago 37

Python Question

You see, most of the posts that discuss image creation deal with a 3D Matrix[0][1][2] that effectively contains the necessary info to apply directly

`img = Image.fromarray(Matrix, 'RGB')`

However, I'm stuck with a massive matrix that has "3n" columns and "n" rows. As you might see, the "image" is coded in a fashion reminding me of P3/P6 formats:

`[ 0 0 0 255 255 255 0 0 0`

0 0 0 255 255 255 0 0 0

255 255 255 0 0 0 255 255 255]

The above 2D matrix represents 3x3 "pixels", and using Image.fromarray produces an image full of holes. I've thinking of splitting it into three (!!!) 2 dimensional arrays and then using

This is what I'm thinking of doing, btw:

`R = np.zeros((Y, X), dtype = np.uint8) # Same for G & B`

for Row in range(Y):

for Column in range(3*X):

if Column % 3 == 0: # With Column-1 for G and -2 for B

R[Row][Column/3] = 2DMatrix[Row][Column]

#After populating R, G, B

RGB0 = np.dstack([R, G, B])

img = Image.fromarray(RGB0, 'RGB')

Thanks!

Answer

`numpy.reshape`

should work for this. It's also important that the color values are 8-bit unsigned:

```
>>> import numpy as np
>>> a = [[0, 0, 0, 255, 255, 255, 0, 0, 0],
... [0, 0, 0, 255, 255, 255, 0, 0, 0],
... [255, 255, 255, 0, 0, 0, 255, 255, 255]]
>>> a = np.array(a)
>>> a.astype('u1').reshape((3,3,3))
array([[[ 0, 0, 0],
[255, 255, 255],
[ 0, 0, 0]],
[[ 0, 0, 0],
[255, 255, 255],
[ 0, 0, 0]],
[[255, 255, 255],
[ 0, 0, 0],
[255, 255, 255]]], dtype=uint8)
>>> import PIL.Image
>>> i = PIL.Image.fromarray(a.astype('u1').reshape((3,3,3)), 'RGB')
```

This seems to work the way we would expect:

```
>>> i.size
(3, 3)
>>> i.getpixel((0,0))
(0, 0, 0)
>>> i.getpixel((1,0))
(255, 255, 255)
>>> i.getpixel((2,0))
(0, 0, 0)
>>> i.getpixel((0,1))
(0, 0, 0)
>>> i.getpixel((1,1))
(255, 255, 255)
>>> i.getpixel((2,1))
(0, 0, 0)
>>> i.getpixel((0,2))
(255, 255, 255)
>>> i.getpixel((1,2))
(0, 0, 0)
>>> i.getpixel((2,2))
(255, 255, 255)
```

Source (Stackoverflow)