Building a paint application with Python and Tkinter

Python Tkinter Canvas and Graphics: Exercise-2 with Solution

Write a Python program to design a paint application using Tkinter where the user can draw on the Canvas widget with different colors.

Sample Solution:

Python Code:

import tkinter as tk

# Global variables to track drawing state
drawing = False
last_x, last_y = None, None
pen_color = "black"

def start_drawing(event):
    global drawing
    drawing = True
    global last_x, last_y
    last_x, last_y = event.x, event.y

def stop_drawing(event):
    global drawing
    drawing = False

def draw(event):
    global last_x, last_y

    if drawing:
        x, y = event.x, event.y
        canvas.create_line((last_x, last_y, x, y), fill=pen_color, width=2)
        last_x, last_y = x, y

def change_color(new_color):
    global pen_color
    pen_color = new_color

root = tk.Tk()
root.title("Paint Application")

canvas = tk.Canvas(root, width=400, height=300, bg="white")
canvas.pack()

colors = ["red", "green", "blue", "black", "orange", "pink"]

color_buttons = []
for color in colors:
    color_buttons.append(tk.Button(root, text=color.capitalize(), bg=color, command=lambda c=color: change_color(c)))
    color_buttons[-1].pack(side=tk.LEFT)

canvas.bind("<Button-1>", start_drawing)
canvas.bind("<ButtonRelease-1>", stop_drawing)
canvas.bind("<B1-Motion>", draw)

root.mainloop()

Explanation:

In the exercise above -

• Import the Tkinter library (tkinter).
• Define global variables to track drawing state (drawing), last position ('last_x', 'last_y'), and pen color ('pen_color').
• Define functions to handle drawing: start_drawing(event): Sets drawing to True and records the initial mouse position. stop_drawing(event): Sets drawing to False when the mouse button is released.
• draw(event): Draws lines on the canvas if drawing is True, connecting the last recorded position to the current mouse position.
• Create the main "Tkinter" window (root) with the title "Paint Application."
• Create a canvas (canvas) for drawing with a white background.
• Define a list of color names (colors) for the pen.
• Create color buttons for each color in the list, associating each button with the change_color() function to change the pen color.
• Bind mouse events to the canvas:
• The main event loop, root.mainloop(), starts the Tkinter application.

Output:

Flowchart:

Python Code Editor:

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