Tkinter - Canvas

https://tkinter-docs.readthedocs.io/en/latest/widgets/canvas.html

https://python-course.eu/tkinter/canvas-widgets-in-tkinter.php

INTRODUCTION

The Canvas widget supplies graphics facilities for Tkinter.

# canvas1.py
import tkinter as tk

root = tk.Tk()

canvas_width, canvas_height = 400, 300
canvas = tk.Canvas(root, width=canvas_width, height=canvas_height)
canvas.grid()

# adding items ...
y = canvas_height // 2
canvas.create_line(0, y, canvas_width, y, fill="red", width=5)

root.mainloop()

Selected keyword arguments in Canvas()

master=root   # the first argument
width=canvas_width
height=canvas_height
bg="white"   # or background="white"
bd=5   # borderwidth
relief="flat"

Selected methods [canvas1a.py]

# item_id = canvas.create_line(xy, **options)
# xy : x1, y1, x2, y2   # 4 positional arguments
# or (x1, y1, x2, y2)   # 4-tuple (left, top, right, bottom)
# or ((x1, y1), (x2, y2))   # 2 pairs
# options : fill="red", dash=(4, 4), width=3

# item_id = canvas.create_rectangle(xy, **options)
# xy : top left, bottom right
# options : fill="blue", outline="red", width=2

# item_id = canvas.create_arc(xy, **options)

# item_id = canvas.create_oval(xy, **options)
# xy : top left, bottom right (the bounding box)
# options : fill="yellow", outline="red", width=3

# item_id = canvas.create_polygon(xy, **options)
# xy : minimum 3 points (3 pairs or 6 numbers)
# options : fill="yellow", outline="red", width=3

# item_id = canvas.create_text(xy, **options)
canvas.create_text(x1, y1, text="Python", font="Times 20 bold")

# item_id = canvas.create_window(xy, **options)
canvas.create_window(x1, y1, window=widget)   # embed a widget [canvas4.py]

canvas.coords(item_id, new_xy)   # change coordinates
canvas.itemconfig(item_id, fill="blue")   # change color for the item [canvas1b.py]
canvas.delete(item_id)   # remove item
canvas.delete(tk.ALL)   # remove all items
canvas.tkraise(item_id)   # raise item to front
canvas.lower(item_id)   # lower item below others
canvas.move(item_id, offset_x, offset_y)   # move item by offset

def create_circle(canvas, x, y, r):
   item_id = canvas.create_oval(x-r, y-r, x+r, y+r)
   return item_id

INTERACTIVE PAINTING

# canvas2.py
import tkinter as tk

def paint(event):
    radius = 2
    x1, y1 = (event.x - radius), (event.y - radius)
    x2, y2 = (event.x + radius), (event.y + radius)
    canvas.create_oval(x1, y1, x2, y2, fill="green")

root = tk.Tk()   # root widget

canvas_width, canvas_height = 400, 300
canvas = tk.Canvas(root, width=canvas_width, height=canvas_height)
canvas.grid()
canvas.bind("<B1-Motion>", paint)

message = tk.Label(root, text="Press and Drag the mouse to draw")
message.grid()

root.mainloop()

IMAGES

# canvas3.py
import tkinter as tk
from PIL import Image, ImageTk

root = tk.Tk()   # root widget

canvas_width, canvas_height = 600, 300
canvas = tk.Canvas(root, width=canvas_width, height=canvas_height)
canvas.grid()

#logo = tk.PhotoImage(file="img/python_logo.png")
#logo = tk.PhotoImage(file="img/python_logo.gif")
#logo = tk.PhotoImage(file="img/python_logo.jpg")   # _tkinter.TclError, we need PIL

im = Image.open("img/python_logo.jpg")
logo = ImageTk.PhotoImage(im)
print("width {} height {}".format(logo.width(), logo.height()))

canvas.create_image(20, 20, anchor=tk.NW, image=logo)

root.mainloop()