Problem plotting an image's Fourier transforms. “ValueError: x and y can be no greater than 2-D, but have shapes (2592,) and (2592, 1, 3)”

问题

I'm trying to get the fft of an image and then plot the fraq of that fft with using matplotlib. However, this error message:

"ValueError: x and y can be no greater than 2-D, but have shapes (2592,) and (2592, 1, 3)".

I tried to reshape my np.array like so:

import numpy as np
from PIL import Image
import matplotlib.pyplot as plt
import tkinter
from scipy.fftpack import fft, fft2, fftshift

resim = Image.open(r'yeni.jpg')

resim_data = np.asarray(resim)

fourier = fft2(resim_data)

#psd2D = np.abs(fourier)**2


plt.figure()
plt.semilogy(abs(fourier).astype(np.uint8))
plt.title('fourier transform fraq')
plt.show()

ERROR MESSAGE BLELOW:

Traceback (most recent call last):

File "myfrouier.py", line 21, in

plt.semilogy(abs(fourier).astype(np.uint8)) File

"/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/pyplot.py",

line 2878, in semilogy return gca().semilogy(*args, **kwargs)
File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 1844, in semilogy l = self.plot(*args, **kwargs) File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/init.py", line 1810, in inner return func(ax, *args, **kwargs)
File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 1611, in plot for line in self._get_lines(*args, **kwargs):
File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 393, in _grab_next_args yield from self._plot_args(this, kwargs) File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 370, in _plot_args x, y = self._xy_from_xy(x, y) File "/home/aybarsyildiz/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 234, in _xy_from_xy "shapes {} and {}".format(x.shape, y.shape)) ValueError: x and y can be no greater than 2-D, but have shapes (2592,) and (2592, 1, 3)

回答1:

You don't seem to have the necessary 2d-array, but an array with an additional third dimension. You have to choose what you want to do with that dimension:

• If you only need the information of one channel, you can choose to keep only the n-th values of the third dimension:

  n = 1
  resim_data = resim_data[:, :, n]
  

• Calculate the mean for all values of the third dimension

  resim_data = resim_data.mean(axis=-1)
  

• Choose the maximum value for all values of the third dimension

  resim_data = resim_data.max(axis=-1)
  

• ...

---

Example:

I used your code with an example image with 244x244 pixels and got a similar error to yours:

ValueError: x and y can be no greater than 2-D, but have shapes (244,) and (244, 244, 4)

I was only interested in the first channel, so I dropped all other unnecessary values from the third dimension:

resim_data = np.asarray(resim)
print(resim_data.shape)
n = 0
resim_data = resim_data[:, :, n]
print(resim_data.shape)

Which prints:

(244, 244, 4)
(244, 244)

As you can see, resim_data has no third dimension any more. No errors after that.

来源：https://stackoverflow.com/questions/53944197/problem-plotting-an-images-fourier-transforms-valueerror-x-and-y-can-be-no-g