Python: Maze generation using PIL

This page uses Python to do recursive maze generation using the PIL (Python Imaging Library).

Here are links to a series on recursive maze generation and visualization

2021-02-19: Maze algorithm explanation using GIF images
2021-02-22: Lua: Maze generation with static SVG
2021-02-24: JavaScript: Maze generation with dynamic SVG
2021-02-27: JavaScript: Maze generation with dynamic SVG and D3
2021-02-25: R: Maze generation using grid
2021-03-04: Julia: Maze generation using Luxor
2021-02-26: Python: Maze generation using PIL (this page)
2021-03-04: Java: Maze generation using AWT
2021-03-02: C#: Maze generation

(more coming) It is sometimes useful to create custom images in Python. The ImageDraw class in the PIL can be useful for this.

One can create new images or read and annotate existing images.

It as always useful to create a custom class. But, for example purposes, no classes are used.

The ImageDraw class uses colors are represented as a tuple of the integer values for red, green, and blue. I find it easier to work with the hex forms of red, green and blue. The color method converts from hex to a tuple representation.

def color(hex1):
	r1 = int(hex1[0:2],16)
	g1 = int(hex1[2:4],16)
	b1 = int(hex1[4:6],16)
	return (r1,g1,b1)

color of "000000" returns (0,0,0), black.
color of "FF0000" returns (255,0,0), red.
color of "00FF00" returns (0,255,0), green.
color of "0000FF" returns (0,0,255), blue.
color of "FFFFFF" returns (255,255,255), white.

A Lua command line console program is now presented to create a maze as an image.

This may not be the best Lua program for this task, but is sufficient for the present purposes.

The global variable linesCount1 is used, in part to show how global variables can be used, when appropriate, as some languages require special handling or access mechanisms for global variables.

Here is a pseudo-code for the maze generation algorithm as described to make a maze of rows and columns.

Main: Start with an empty canvas. Outline the maze limits with an entry and exit point on opposite sides. Call MazeGenerate with the rows and columns to be filled in. MazeGenerate: If the rows and columns requested are both greater than 1 Then If the height is greater than the width Then Divide the grid into top and bottom parts. Draw a (horizontal) line between the parts, leaving a gap to pass through. Call MazeGenerate on the top part Call MazeGenerate on the bottom part Else Divide the grid into left and right parts. Draw a (vertical) line between the parts, leaving a gap to pass through. Call MazeGenerate on the left part Call MazeGenerate on the right part End If End If

The actual code fills in details that are not needed at the higher level of the algorithm description. For example, the side and gap lengths, and exact x and y coordinates are omitted. As another example, the division into parts can be done using pseudo-random numbers, but that is omitted from the algorithm.

For more information, see the following: Maze algorithm explanation using GIF images Here is the Python code [#2]

import os
import random
import math
import PIL
from PIL import Image
from PIL import ImageDraw
linesCount1 = 0
draw1 = None
def color(hex1):
	r1 = int(hex1[0:2],16)
	g1 = int(hex1[2:4],16)
	b1 = int(hex1[4:6],16)
	return (r1,g1,b1)
def lineAdd1(n1, x1, y1, x2, y2):
	if (x1 != x2) or (y1 != y2):
		global linesCount1
		linesCount1 += 1
		draw1.line((x1,y1,x2,y2),fill=color("000000"),width=1)
		print("{0:d}. ( {1:d} , {2:d} ) to ( {3:d} , {4:d} )".format(linesCount1,x1,y1,x2,y2))
def mazeMake2(n1, rlen1, clen1, side1, x1, y1):
	if (rlen1 <= 1) or (clen1 <= 1):
		return
	x3 = x1+side1*clen1
	y3 = y1+side1*rlen1
	n2 = n1+1
	r1 = random.random()
	c1 = random.random()
	if rlen1 > clen1:
		cpos1 = math.floor(c1*clen1)
		rpos1 = math.floor(r1*(rlen1-1))+1
		x2 = x1+side1*cpos1
		y2 = y1+side1*rpos1
		lineAdd1(n2,x1,y2,x2,y2)
		lineAdd1(n2,x2+side1,y2,x3,y2)
		mazeMake2(n2,rpos1,clen1,side1,x1,y1)
		mazeMake2(n2,rlen1-rpos1,clen1,side1,x1,y2)
	else:
		cpos1 = math.floor(c1*(clen1-1))+1
		rpos1 = math.floor(r1*rlen1)
		x2 = x1+side1*cpos1
		y2 = y1+side1*rpos1
		lineAdd1(n2,x2,y1,x2,y2)
		lineAdd1(n2,x2,y2+side1,x2,y3)
		mazeMake2(n2,rlen1,cpos1,side1,x1,y1)
		mazeMake2(n2,rlen1,clen1-cpos1,side1,x2,y1)
def mazeMake1(rlen1, clen1, side1, gap1):
	x1 = side1*gap1
	y1 = side1*gap1
	x3 = x1+side1*clen1
	y3 = y1+side1*rlen1
	lineAdd1(0,x1,y3,x3,y3)
	lineAdd1(0,x1,y1,x3,y1)
	lineAdd1(0,x1,y1,x1,y3-side1)
	lineAdd1(0,x3,y1+side1,x3,y3)
	mazeMake2(1,rlen1,clen1,side1,x1,y1)
def mazeMake0():
	rlen1 = 8
	clen1 = 12
	side1 = 10
	gap1 = 1
	random.seed(12345)
	width1 = side1*(gap1+clen1+gap1)
	height1 = side1*(gap1+rlen1+gap1)
	linesCount1 = 0
	imageFs2 = "D:\\W\\PROGRAM1.IMG\\ds1.draw-20-01.png"
	print("Create a {0:d} x {1:d} image as \"{2:s}\".".format(width1,height1,imageFs2))
	print("")
	image1 = Image.new("RGB",(width1,height1),color("FFFFFF"))
	global draw1
	draw1 = ImageDraw.Draw(image1)
	mazeMake1(rlen1,clen1,side1,gap1)
	image1.save(imageFs2)
mazeMake0()

Here is the output of the Python code.

Create a 140 x 100 image as "D:\W\PROGRAM1.IMG\ds1.draw-20-01.png".
1. ( 10 , 90 ) to ( 130 , 90 )
2. ( 10 , 10 ) to ( 130 , 10 )
3. ( 10 , 10 ) to ( 10 , 80 )
4. ( 130 , 20 ) to ( 130 , 90 )
5. ( 20 , 10 ) to ( 20 , 40 )
6. ( 20 , 50 ) to ( 20 , 90 )
7. ( 50 , 10 ) to ( 50 , 70 )
8. ( 50 , 80 ) to ( 50 , 90 )
9. ( 30 , 40 ) to ( 50 , 40 )
10. ( 30 , 10 ) to ( 30 , 20 )
11. ( 30 , 30 ) to ( 30 , 40 )
12. ( 40 , 20 ) to ( 50 , 20 )
13. ( 40 , 20 ) to ( 40 , 30 )
14. ( 20 , 70 ) to ( 30 , 70 )
15. ( 40 , 70 ) to ( 50 , 70 )
16. ( 30 , 40 ) to ( 30 , 60 )
17. ( 40 , 60 ) to ( 50 , 60 )
18. ( 40 , 40 ) to ( 40 , 50 )
19. ( 30 , 70 ) to ( 30 , 80 )
20. ( 40 , 80 ) to ( 40 , 90 )
21. ( 120 , 10 ) to ( 120 , 30 )
22. ( 120 , 40 ) to ( 120 , 90 )
23. ( 50 , 80 ) to ( 100 , 80 )
24. ( 110 , 80 ) to ( 120 , 80 )
25. ( 110 , 20 ) to ( 110 , 80 )
26. ( 50 , 70 ) to ( 90 , 70 )
27. ( 100 , 70 ) to ( 110 , 70 )
28. ( 60 , 10 ) to ( 60 , 20 )
29. ( 60 , 30 ) to ( 60 , 70 )
30. ( 60 , 40 ) to ( 100 , 40 )
31. ( 90 , 10 ) to ( 90 , 20 )
32. ( 90 , 30 ) to ( 90 , 40 )
33. ( 80 , 20 ) to ( 80 , 40 )
34. ( 60 , 30 ) to ( 70 , 30 )
35. ( 70 , 10 ) to ( 70 , 20 )
36. ( 100 , 30 ) to ( 110 , 30 )
37. ( 100 , 10 ) to ( 100 , 20 )
38. ( 90 , 50 ) to ( 90 , 70 )
39. ( 80 , 40 ) to ( 80 , 50 )
40. ( 80 , 60 ) to ( 80 , 70 )
41. ( 70 , 50 ) to ( 80 , 50 )
42. ( 70 , 50 ) to ( 70 , 60 )
43. ( 100 , 50 ) to ( 110 , 50 )
44. ( 100 , 50 ) to ( 100 , 60 )

Here is the image created by the Python code. Maze