Converting multi-dimensional array to a tuple in python

Question

I am getting some frame data from a web cam in the form of rgb values.

import numpy as np    
frame = get_video()
print np.shape(frame)

The output is (480, 640, 3). Now I want to construct image from these values. So, I want to use

im = Image.new("RGB", (480, 640),frame)

But, here the third argument takes a tuple. I get this error

SystemError: new style getargs format but argument is not a tuple

So, my question is what is the best way to convert this frame data to a tuple, so that I can construct my image.

get_video() gets the RGB values of the video frame. So basically frame contains 480x640 RGB values. — kosta
– kosta, Commented Jun 20, 2015 at 5:37

Antonio Lutfi · Accepted Answer · 2015-06-20 19:55:38Z

1

I am assuming here that you are importing the class Image from PIL.

The documentation for Image.new(), accessed with console command Image.new? is:

In [3]: Image.new?
Type: function
Base Class:
String Form:
Namespace: Interactive
File: /usr/lib/python2.7/dist-packages/PIL/Image.py
Definition: Image.new(mode, size, color=0)
Docstring: Create a new image

The third parameter is an RGB color, such as (255,255,255), to fill the hole image. You can't initialize individual pixels with this function.

I am also assuming that frame is a 3D array. As your output suggests, it's 480 lines and 640 rows of RGB tuples.

I don't know if there is a simpler way to do this, but I would set the pixel values by the putpixel() function, something like:

im = Image.new( "RGB", (480, 640), (0, 0, 0) ) #initialize 480:640 black image
for i in range(480):
    for j in range(640):
        im.putpixel( (i, j), tuple(frame[i][j]) )

Always check the docstring via console, it saves a lot of time. I also recommend using ipython as your console.

edited Jun 20, 2015 at 19:55

answered Jun 20, 2015 at 6:45

Antonio Lutfi

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2 Comments

kosta Over a year ago

Thanks a lot. I will accept your answer if you replace im.putpixel( (i, j), frame[i][j] ) with im.putpixel( (i, j), tuple(frame[i][j]) ). It works well, but I am actually trying to live stream this video and it works very slow. Is there a better way to do this?

Antonio Lutfi Over a year ago

Done. It could be a better way, I've never actually used PIL.

kosta · Accepted Answer · 2015-06-20 08:27:12Z

0

I found this implementation to be faster

from PIL import Image

im = Image.new("RGB", (480, 640), (0, 0, 0) ) #initialize 480:640 black image
while True:
 frame = get_video()
 im = Image.fromarray(frame)
 im.save('some-name', 'JPEG')

answered Jun 20, 2015 at 8:27

kosta

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