Problems saving arrays as greyscale 'L' images using matplotlib? - arrays

Question

I'm trying to save an array as an image using plt.imsave(). The original image is a 16 greyscale 'L' tiff. But I keep on getting the error:
Attribute error: 'str' object has no attribute 'shape'
figsize = [x / float(dpi) for x in (arr.shape[1], arr.shape[0])]
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
import numpy as np
from PIL import Image
im2=plt.imread('C:\Documents\Image\pic.tif')
plt.imsave(im2, '*.tif')
The image is 2048x2048, the array is 2048Lx2048L. Everything I've tried doesn't work: shape=[2048,2048], im2.shape(2048,2048). Can anybody tell me out how to add shape as a keyword argument? Or is there any easier way to do this, preferably avoiding PIL, since it seems to have issues with 16-bit greyscale tiffs and I absolutely have to use that format?

Answer 1

I think you've got the arguments backwards. From help(plt.imsave):
Help on function imsave in module matplotlib.pyplot:
imsave(*args, **kwargs)
Saves a 2D :class:`numpy.array` as an image with one pixel per element.
The output formats available depend on the backend being used.
Arguments:
*fname*:
A string containing a path to a filename, or a Python file-like object.
If *format* is *None* and *fname* is a string, the output
format is deduced from the extension of the filename.
*arr*:
A 2D array.
i.e.:
>>> im2.shape
(256, 256)
>>> plt.imsave(im2, "pic.tif")
Traceback (most recent call last):
File "<ipython-input-36-a7bbfaeb1a4c>", line 1, in <module>
plt.imsave(im2, "pic.tif")
File "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 1753, in imsave
return _imsave(*args, **kwargs)
File "/usr/lib/pymodules/python2.7/matplotlib/image.py", line 1230, in imsave
figsize = [x / float(dpi) for x in arr.shape[::-1]]
AttributeError: 'str' object has no attribute 'shape'
>>> plt.imsave("pic.tif", im2)
>>>