皮耶·蒙德里安是 20 世纪的荷兰画家，也是抽象艺术运动“新塑料主义”的创始人之一。他最具标志性的画作依赖于原色（蓝、黄、红）、黑色和白色。他采用极简主义的方法，用水平和垂直的元素将这些颜色分开。
这个程序随机生成遵循蒙德里安风格的绘画。你可以在en.wikipedia.org/wiki/Piet_Mondrian找到更多关于皮特·蒙德里安的信息。
bext模块允许我们的 Python 程序在文本输出中显示明亮的原色，尽管这本书只显示黑白图像。图 47-1 显示了运行mondrian.py时的输出。
图 47-1 :蒙德里安艺术程序的计算机生成艺术。程序每次运行都会生成不同的图像。
该算法通过创建一个带有随机间隔的垂直线和水平线的数据结构（canvas字典）来工作，如图图 47-2 。
:蒙德里安艺术算法的第一步是创建一个网格。
接下来，它移除一些线段来创建更大的矩形，如图图 47-3 所示。
:蒙德里安艺术算法的第二步随机去掉一些线条。
最后，算法用黄色、红色、蓝色或黑色随机填充一些矩形，如图图 47-4 。
:蒙德里安艺术算法第三步随机选择矩形填充颜色。
你可以在github.com/asweigart/mondrian_art_generator找到这个蒙德里安艺术生成器的另一个版本，还有一些样本图片。
"""Mondrian Art Generator, by Al Sweigart email@protected
Randomly generates art in the style of Piet Mondrian.
More info at: https://en.wikipedia.org/wiki/Piet_Mondrian
This code is available at https://nostarch.com/big-book-small-python-programming
Tags: large, artistic, bext"""
import sys, random
try:
import bext
except ImportError:
print('This program requires the bext module, which you')
print('can install by following the instructions at')
print('https://pypi.org/project/Bext/')
sys.exit()
# Set up the constants:
MIN_X_INCREASE = 6
MAX_X_INCREASE = 16
MIN_Y_INCREASE = 3
MAX_Y_INCREASE = 6
WHITE = 'white'
BLACK = 'black'
RED = 'red'
YELLOW = 'yellow'
BLUE = 'blue'
# Setup the screen:
width, height = bext.size()
# We can't print to the last column on Windows without it adding a
# newline automatically, so reduce the width by one:
width -= 1
height -= 3
while True: # Main application loop.
# Pre-populate the canvas with blank spaces:
canvas = {}
for x in range(width):
for y in range(height):
canvas[(x, y)] = WHITE
# Generate vertical lines:
numberOfSegmentsToDelete = 0
x = random.randint(MIN_X_INCREASE, MAX_X_INCREASE)
while x < width - MIN_X_INCREASE:
numberOfSegmentsToDelete += 1
for y in range(height):
canvas[(x, y)] = BLACK
x += random.randint(MIN_X_INCREASE, MAX_X_INCREASE)
# Generate horizontal lines:
y = random.randint(MIN_Y_INCREASE, MAX_Y_INCREASE)
while y < height - MIN_Y_INCREASE:
numberOfSegmentsToDelete += 1
for x in range(width):
canvas[(x, y)] = BLACK
y += random.randint(MIN_Y_INCREASE, MAX_Y_INCREASE)
numberOfRectanglesToPaint = numberOfSegmentsToDelete - 3
numberOfSegmentsToDelete = int(numberOfSegmentsToDelete * 1.5)
# Randomly select points and try to remove them.
for i in range(numberOfSegmentsToDelete):
while True: # Keep selecting segments to try to delete.
# Get a random start point on an existing segment:
startx = random.randint(1, width - 2)
starty = random.randint(1, height - 2)
if canvas[(startx, starty)] == WHITE:
continue
# Find out if we're on a vertical or horizontal segment:
if (canvas[(startx - 1, starty)] == WHITE and
canvas[(startx + 1, starty)] == WHITE):
orientation = 'vertical'
elif (canvas[(startx, starty - 1)] == WHITE and
canvas[(startx, starty + 1)] == WHITE):
orientation = 'horizontal'
else:
# The start point is on an intersection,
# so get a new random start point:
continue
pointsToDelete = [(startx, starty)]
canDeleteSegment = True
if orientation == 'vertical':
# Go up one path from the start point, and
# see if we can remove this segment:
for changey in (-1, 1):
y = starty
while 0 < y < height - 1:
y += changey
if (canvas[(startx - 1, y)] == BLACK and
canvas[(startx + 1, y)] == BLACK):
# We've found a four-way intersection.
break
elif ((canvas[(startx - 1, y)] == WHITE and
canvas[(startx + 1, y)] == BLACK) or
(canvas[(startx - 1, y)] == BLACK and
canvas[(startx + 1, y)] == WHITE)):
# We've found a T-intersection; we can't
# delete this segment:
canDeleteSegment = False
break
else:
pointsToDelete.append((startx, y))
elif orientation == 'horizontal':
# Go up one path from the start point, and
# see if we can remove this segment:
for changex in (-1, 1):
x = startx
while 0 < x < width - 1:
x += changex
if (canvas[(x, starty - 1)] == BLACK and
canvas[(x, starty + 1)] == BLACK):
# We've found a four-way intersection.
break
elif ((canvas[(x, starty - 1)] == WHITE and
canvas[(x, starty + 1)] == BLACK) or
(canvas[(x, starty - 1)] == BLACK and
canvas[(x, starty + 1)] == WHITE)):
# We've found a T-intersection; we can't
# delete this segment:
canDeleteSegment = False
break
else:
pointsToDelete.append((x, starty))
if not canDeleteSegment:
continue # Get a new random start point.
break # Move on to delete the segment.
# If we can delete this segment, set all the points to white:
for x, y in pointsToDelete:
canvas[(x, y)] = WHITE
# Add the border lines:
for x in range(width):
canvas[(x, 0)] = BLACK # Top border.
canvas[(x, height - 1)] = BLACK # Bottom border.
for y in range(height):
canvas[(0, y)] = BLACK # Left border.
canvas[(width - 1, y)] = BLACK # Right border.
# Paint the rectangles:
for i in range(numberOfRectanglesToPaint):
while True:
startx = random.randint(1, width - 2)
starty = random.randint(1, height - 2)
if canvas[(startx, starty)] != WHITE:
continue # Get a new random start point.
else:
break
# Flood fill algorithm:
colorToPaint = random.choice([RED, YELLOW, BLUE, BLACK])
pointsToPaint = set([(startx, starty)])
while len(pointsToPaint) > 0:
x, y = pointsToPaint.pop()
canvas[(x, y)] = colorToPaint
if canvas[(x - 1, y)] == WHITE:
pointsToPaint.add((x - 1, y))
if canvas[(x + 1, y)] == WHITE:
pointsToPaint.add((x + 1, y))
if canvas[(x, y - 1)] == WHITE:
pointsToPaint.add((x, y - 1))
if canvas[(x, y + 1)] == WHITE:
pointsToPaint.add((x, y + 1))
# Draw the canvas data structure:
for y in range(height):
for x in range(width):
bext.bg(canvas[(x, y)])
print(' ', end='')
print()
# Prompt user to create a new one:
try:
input('Press Enter for another work of art, or Ctrl-C to quit.')
except KeyboardInterrupt:
sys.exit() 在输入源代码并运行几次之后，尝试对其进行实验性的修改。你也可以自己想办法做到以下几点：
- 用不同的调色板创建程序。
- 使用
Pillow模块制作蒙德里安艺术的图像文件。你可以从《Python 自动化指南》第 19 章了解这个模块，automatetheboringstuff.com/2e/chapter19。
试着找出下列问题的答案。尝试对代码进行一些修改，然后重新运行程序，看看这些修改有什么影响。
- 如果把第 41 行的
canvas[(x, y)] = WHITE改成canvas[(x, y)] = RED会出现什么错误？ - 如果把 176 行的
print(' ', end='')改成print('A', end='')会怎么样？