I have a python code like this:
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
img = mpimg.imread('xxx.png')
fig = plt.figure(figsize=(8,10))
ax1 = fig.add_axes([0., 0.92, 0.1, 0.08])
ax1.imshow(img)
ax1.axvline(0.5, 0, 1, color='gray')
plt.show()
Running this code shows the img in the axes area. However, the vline does not show up.
If I remove the line: ax1.imshow(img) and run again I do see the vline.
Any suggestion?
Your line is probably being drawn over on the left hand y-axis. The x coordinate of ax.axvline is in data coordinates. The x-axis limits from the ax.imshow will be the number of pixels in the x-direction of the image. So, an x coordinate of 0.5 will be in the centre of the left-most pixel of the imshow.
Try increasing the x coordinate of the axvline to a bigger number, and you will probably see it.
From the axvline docs:
x : scalar, optional, default: 0 x position in data coordinates of the vertical line.
Consider this example:
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
img = mpimg.imread('stinkbug.png')
fig, ax = plt.subplots(1)
ax.imshow(img)
ax.axvline(0.5, 0, 1, color='blue')
ax.axvline(200, 0, 1, color='red')
plt.show()
Note the blue line right against the left hand y-axis.
