Matplotlib imshow() orientation
In imshow(), the second index is aligned with the “x” axis. And [0,0] is in the upper left. So both `origin=”lower”’ and a transpose are needed in most cases to align [i,j] with [x,y].
nx = 512
ny = 512
image = np.zeros((nx,ny))
for i in range(nx):
for j in range(ny):
image[i,j] = np.sin(2*np.pi*float(i)/float(nx)) + np.sin(6*np.pi*float(y)/float(ny))
plt.imshow(image.T,origin="lower")