Python Tkinter – Canvas Widget

Tkinter is a GUI toolkit used in python to make user-friendly GUIs.Tkinter is the most commonly used and the most basic GUI framework available in python. Tkinter uses an object-oriented approach to make GUIs.
Note: For more information, refer to Python GUI – tkinter

Canvas widget

The Canvas widget lets us display various graphics on the application. It can be used to draw simple shapes to complicated graphs. We can also display various kinds of custom widgets according to our needs.

Syntax:

C = Canvas(root, height, width, bd, bg, ..)

Optional parameters: 

• root = root window.
• height = height of the canvas widget.
• width = width of the canvas widget.
• bg = background colour for canvas.
• bd = border of the canvas window.
• scrollregion (w, n, e, s)tuple defined as a region for scrolling left, top, bottom and right.
• highlightcolor colour shown in the focus highlight.
• cursor It can be defined as a cursor for the canvas which can be a circle, a do, an arrow etc.
• confine decides if canvas can be accessed outside the scroll region.
• relief type of the border which can be SUNKEN, RAISED, GROOVE and RIDGE. 
  

Some common drawing methods:

• Creating an Oval

 oval = C.create_oval(x0, y0, x1, y1, options)

• Creating an arc

 arc = C.create_arc(20, 50, 190, 240, start=0, extent=110, fill="red")

• Creating a Line

 line = C.create_line(x0, y0, x1, y1, ..., xn, yn, options)

• Creating a polygon

 oval = C.create_polygon(x0, y0, x1, y1, ...xn, yn, options)

Example 1: Simple Shapes Drawing 

Python3

from tkinter import *


root = Tk()

C = Canvas(root, bg="yellow",
           height=250, width=300)

line = C.create_line(108, 120,
                     320, 40,
                     fill="green")

arc = C.create_arc(180, 150, 80,
                   210, start=0,
                   extent=220,
                   fill="red")

oval = C.create_oval(80, 30, 140,
                     150,
                     fill="blue")

C.pack()
mainloop()

Output:

Example 2: Simple Paint App 

Python3

from tkinter import *


root = Tk()

# Create Title
root.title(  "Paint App ")

# specify size
root.geometry("500x350")

# define function when
# mouse double click is enabled
def paint( event ):

    # Co-ordinates.
    x1, y1, x2, y2 = ( event.x - 3 ),( event.y - 3 ), ( event.x + 3 ),( event.y + 3 )

    # Colour
    Colour = "#000fff000"

    # specify type of display
    w.create_line( x1, y1, x2,
                  y2, fill = Colour )


# create canvas widget.
w = Canvas(root, width = 400, height = 250)

# call function when double
# click is enabled.
w.bind( "<B1-Motion>", paint )

# create label.
l = Label( root, text = "Double Click and Drag to draw." )
l.pack()
w.pack()

mainloop()

Output: