Image plotted from a FITS file with matplotlib oriented incorrectly

问题

I'm having a little issue with something regarding plotting a fits image using matplotlib's imshow. It seems that my image is flipped both horizontally and vertically. I'm sure there is something simple I am overlooking, if anyone could point me in the right direction that would be great.

This is what my image should look like:

So, I'm loading my image as:

from astropy.io import fits
import matplotlib
import matplotlib.pyplot as pyplot
#Opening/reading in my fits file
hdulist = fits.open('.../myfits.fits')
#Accessing the image data and specifying the dimensions I wish to use
my_image = hdulist[0].data[0,0:,0:]
#Plotting the image
pyplot.imshow(image_SWIFT_uvm2_plot, cmap='gray', vmin=0, vmax=0.5)
pyplot.show()

This is what my image in the plot looks like (the plot is a little more complex than the code I have included, but I have given the critical lines as, hopefully, a self-sufficient code):

Those of you with keen eyes should see that the image has flipped both horizontally and vertically.

回答1:

For FITS files the convention is that the origin is at the lower left hand corner of the image, so you need to use origin='lower' (by default Matplotlib uses origin='upper').

回答2:

I have never used the astropy module, but I know that PyFITS opens the image data as a NumPy array (and from what I'm reading, astropy.io.fits has inherited the functionality of PyFITS anyway, so it should work the same way). If that is the case, then you may use numpy.fliplr and numpy.flipud to flip the array to your desired orientation. Just replace the line

pyplot.imshow(image_SWIFT_uvm2_plot, cmap='gray', vmin=0, vmax=0.5)

with

import numpy as np
pyplot.imshow(np.fliplr(np.flipud(image_SWIFT_uvm2_plot)), cmap='gray',
    vmin=0, vmax=0.5)

Alternatively, you could do a little linear algebra to flip it, or just note that performing both of these flips is the same as using np.rot90 twice

pyplot.imshow(np.rot90(image_SWIFT_uvm2_plot, k=2), cmap='gray', vmin=0, vmax=0)

来源：https://stackoverflow.com/questions/37778651/image-plotted-from-a-fits-file-with-matplotlib-oriented-incorrectly