How to display the coordinates of the points clicked on the image in Google Colab?

Question

I need to locate the mouse click location on an image in a google colab notebook. I tried the following script but nothing happened. The following code should work in Jupyter notebooks but it doesn't work on google colab:

import matplotlib
matplotlib.use('TKAgg')
import matplotlib.pyplot as plt
import matplotlib.image as mpimg

f1 = 'sample.tif'

fig = plt.figure(figsize=(20,30))

img = mpimg.imread(f1)

def onclick(event):
    ix, iy = event.xdata, event.ydata
    print(ix, iy)

cid = fig.canvas.mpl_connect('button_press_event', onclick)

imgplot = plt.imshow(img)
plt.show()

Answer 1

You need to use an interactive IPython backend, e.g. ipympl:

1. Installation in Colab:

!pip install ipympl
from google.colab import output
output.enable_custom_widget_manager()

2. setup matplotlib to use it:

%matplotlib ipympl

3. test it:

import matplotlib
import matplotlib.pyplot as plt

fig, ax = plt.subplots()

def onclick(event):
    ix, iy = event.xdata, event.ydata
    print(ix, iy)

cid = fig.canvas.mpl_connect('button_press_event', onclick)

Output: