在numpy数组中绘制多边形 [英] Drawing polygons in numpy arrays

问题描述

我正在尝试绘制这样的多边形:

I'm trying to draw polygons like this:

In [1]: canvas = numpy.zeros((12, 12), dtype=int)

In [2]: mahotas.polygon.fill_polygon(
   ...: [(1, 1), (1, 10), (10, 10), (10, 1)],
   ...: canvas)

In [3]: canvas
Out[3]: 
array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]])

不过，我希望得到以下输出:

I'd expect the following output though:

array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]])

为什么[(10,2):(10:10)]仍为零?还有另一种方法可以将填充的多边形绘制到数组上?

Why are [(10,2):(10:10)] still zeros? Is there another way to draw a filled polygon to an array?

推荐答案

这是一个奇怪的结果.我发现，如果您颠倒了点的顺序，则会绘制出完整的图形.换句话说:

It is a strange result. I found that if you reverse the order of the points it draws the complete figure. In other words:

# this is broken
pts = [(1, 1), (1, 10), (10, 10), (10, 1)]
# this works
pts = [(1, 1), (10, 1), (10, 10), (1, 10)]

这是一个测试程序:

import numpy
import mahotas.polygon

def run(n, reverse=0):
    canvas = numpy.zeros((n, n), dtype=int)
    lim = n-2
    print '\n%d x %d, lim=%d reverse=%d' % (n, n, lim, reverse)
    pts = [(1, 1), (1, lim), (lim, lim), (lim, 1), (1, 1)]
    if reverse:
        pts.reverse()
    mahotas.polygon.fill_polygon(pts, canvas)
    return canvas

for rev in (0, 1):
    for n in range(3, 14):
        print run(n, rev)

示例:

6 x 6, lim=4 reverse=0
[[0 0 0 0 0 0]
 [0 1 0 0 1 0]
 [0 1 1 1 1 0]
 [0 1 1 1 1 0]
 [0 1 0 0 0 0]
 [0 0 0 0 0 0]]

6 x 6, lim=4 reverse=1
[[0 0 0 0 0 0]
 [0 1 1 1 1 0]
 [0 1 1 1 1 0]
 [0 1 1 1 1 0]
 [0 1 1 1 1 0]
 [0 0 0 0 0 0]]

这篇关于在numpy数组中绘制多边形的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！