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：
