Fundamental Drawing Algorithms in Computer Graphics - Chapter 4 - [Part 1]

import pygame

# Function to draw a line using the line equation (y = mx + c)
def draw_line_equation(x0, y0, x1, y1):
    # 1. Handle Vertical Line (Infinite slope)
    if x0 == x1:
        for y in range(min(y0, y1), max(y0, y1) + 1):
            screen.set_at((x0, y), Red)
        return  # بنعمل return عشان الكود ميحسبش الميل ويضرب Division by zero

    # 2. Calculate Slope (m) and Y-intercept (c)
    m = (y1 - y0) / (x1 - x0)  # Slope
    c = y0 - m * x0            # Y-intercept

    # 3. Draw the line based on the slope type
    if abs(x1 - x0) > abs(y1 - y0):
        # Shallow line (more horizontal) -> Loop over x
        for x in range(min(x0, x1), max(x0, x1) + 1):
            y = m * x + c
            screen.set_at((x, round(y)), Black)
    else:
        # Steep line (more vertical) -> Loop over y
        for y in range(min(y0, y1), max(y0, y1) + 1):
            x = (y - c) / m
            screen.set_at((round(x), y), Blue)

# ==========================================
# Main Execution Block
# ==========================================
if __name__ == "__main__":
    # Initialize pygame
    pygame.init()

    # Define colors
    Black = (0, 0, 0)
    Red = (255, 0, 0)
    Blue = (0, 0, 255)
    White = (255, 255, 255)

    # Get user input from the console
    print("Enter coordinates (x0, y0, x1, y1) separated by commas:")
    input_str = input("Example -> 50,50,700,500: ")
    x0, y0, x1, y1 = map(int, input_str.split(','))

    # Set up display
    screen = pygame.display.set_mode((800, 600))
    pygame.display.set_caption("Line Drawing Using Line Equation")
    screen.fill(White)

    # Draw the line
    draw_line_equation(x0, y0, x1, y1)

    # Add text labels for start and end points
    font = pygame.font.Font("freesansbold.ttf", 13)

    text_surface1 = font.render(f"({x0},{y0})", True, Black)
    screen.blit(text_surface1, (x0 + 5, y0 - 17))

    text_surface2 = font.render(f"({x1},{y1})", True, Black)
    screen.blit(text_surface2, (x1 + 5, y1 + 3))

    # Update the display to show everything
    pygame.display.flip()

    # Main loop to keep the window open
    running = True
    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_ESCAPE:
                    running = False

        pygame.time.wait(10)  # Reduce CPU usage

    pygame.quit()