Jupyter notebook: let a user inputs a drawing

Question

Simple question but I'm not able to find something out there...

Is there a simple and user friendly tool that can be used within a jupyter-notebook to let the user draw something in black on a white space (let say of size (x,y) pixels) after running a cell?

The drawing has to be returned (or even temporarily saved) as an array/image which can then be used by numpy for example.

Answer 1

you can do that using PIL and tkinter libraries, like:

from PIL import ImageTk, Image, ImageDraw
import PIL
from tkinter import *

width = 200  # canvas width
height = 200 # canvas height
center = height//2
white = (255, 255, 255) # canvas back

def save():
    # save image to hard drive
    filename = "user_input.jpg"
    output_image.save(filename)

def paint(event):
    x1, y1 = (event.x - 1), (event.y - 1)
    x2, y2 = (event.x + 1), (event.y + 1)
    canvas.create_oval(x1, y1, x2, y2, fill="black",width=5)
    draw.line([x1, y1, x2, y2],fill="black",width=5)

master = Tk()

# create a tkinter canvas to draw on
canvas = Canvas(master, width=width, height=height, bg='white')
canvas.pack()

# create an empty PIL image and draw object to draw on
output_image = PIL.Image.new("RGB", (width, height), white)
draw = ImageDraw.Draw(output_image)
canvas.pack(expand=YES, fill=BOTH)
canvas.bind("<B1-Motion>", paint)

# add a button to save the image
button=Button(text="save",command=save)
button.pack()

master.mainloop()

You can modify the save function to read the image using PIL and numpy to have it as an numpy array. hope this helps!

Answer 2

Try ipycanvas with interactive drawing mode. It actually has a demo notebook with interactive drawing that could be easily modified to do exactly what you want. It also has numpy support.