python扫描线填充算法详解

本文实例为大家分享了python扫描线填充算法，供大家参考，具体内容如下

介绍

1.用水平扫描线从上到下扫描由点线段构成的多段构成的多边形。

2.每根扫描线与多边形各边产生一系列交点。将这些交点按照x坐标进行分类，将分类后的交点成对取出，作为两个端点，以所填的色彩画水平直线。

3.多边形被扫描完毕后，填色也就完成。

数据结构

活性边表：

新边表：

代码（使用数组）

import numpy as np
from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont

array = np.ndarray((660, 660, 3), np.uint8)
array[:, :, 0] = 255
array[:, :, 1] = 255
array[:, :, 2] = 255

for i in range(0,660,1):
 array[i,330]=(0,0,0)
for j in range(0,660,1):
 array[330,j]=(0,0,0)

def creat_Net(point, row, y_min,y_max ):
 Net = [([ ] * y_max ) for i in range(y_max )]
 point_count = point.shape[0]
 for j in range(0, point_count):
 x = np.zeros(10)
 first = int(min(point[(j+1)%point_count][1] , point[j][1]))
 x[1] = 1/((point[(j+1)%point_count][1]-point[j][1])/(point[(j+1)%point_count][0]-point[j][0])) # x 的增量
 x[2] = max(point[(j+1)%point_count][1] , point[j][1])
 if(point[(j+1)%point_count][1] < point[j][1]):
  x[0] = point[(j+1)%point_count][0]
 else:
  x[0] = point[j][0]
 Net[first].append(x)
 return Net

def draw_line(i,x ,y ):
 for j in range(int(x),int(y)+1):
 array[330-i,j+330]=(20,20,20)

def polygon_fill(point):
 y_min = np.min(point[:,1])
 y_max = np.max(point[:,1])
 Net = creat_Net(point, y_max - y_min + 1, y_min, y_max)
 x_sort = [] * 3
 for i in range(y_min, y_max):
 x = Net[i]
 if(len(x) != 0):
  for k in x :
  x_sort.append(k)
 x_image = [] * 3
 for cell in x_sort:
  x_image.append(cell[0])
 x_image.sort()
 if(len(x_image) >= 3 and x_image[0]==x_image[1] and x_image[2]>x_image[1]):
  x_image[1] = x_image[2]
 draw_line(i, x_image[0], x_image[1])

 linshi = [] * 3
 for cell in x_sort:
  if cell[2] > i:
  cell[0] += cell[1]
  linshi.append(cell)
 x_sort = linshi[:] 

 x_image = [] * 3
 for cell in x_sort:
 x_image.append(cell[0])
 x_image.sort()

 draw_line(i, x_image[0],x_image[1]) 

def main():
 point = [[55,40], [100,80], [100,160],[55,180], [10,160], [10,80]]
 point = np.array(point)
 polygon_fill( point )
 image = Image.fromarray(array)
 image.save('saomao.jpg')
 image.show() 

if __name__ == "__main__":
 main()

实例：

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