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 2048×2048, 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)
>>>