如何匀称地去除短隔离线

问题描述

我想从MultiLinestring过滤掉所有短（例如，length MultiLinestring。对于孤立的行，我的意思是那些不会touch或intersect其他人。

from shapely.geometry import MultiLinestring
from pprint import pprint
from matplotlib import pyplot
from figures import SIZE,set_limits,plot_line,plot_bounds,color_issimple
from figures import plot_coords as _plot_coords

def plot_coords(ax,ob):
    for line in ob:
        _plot_coords(ax,line,zorder=1)

def plot_lines(ax,ob):
    color = color_issimple(ob)
    for line in ob:
        plot_line(ax,color=color,alpha=0.7,zorder=2)

fig = pyplot.figure(1,figsize=SIZE,dpi=90)

#1: line1 original
ax = fig.add_subplot(121)
mline1 = MultiLinestring([((0,0),(2,0)),((1,(1,1)),2),(3,2)),((3,1))])


plot_coords(ax,mline1)
plot_bounds(ax,mline1)
plot_lines(ax,mline1)

ax.set_title('a) original')
set_limits(ax,-1,4,3)

#2: line2 goal
ax = fig.add_subplot(122)

mline2 = MultiLinestring([((0,2))])

plot_coords(ax,mline2)
plot_bounds(ax,mline2)
plot_lines(ax,mline2)

ax.set_title('b) goal')
set_limits(ax,3)

pyplot.show()

因此，这可以分为两个子问题：

如何选择所有隔离的行？
如何按长度过滤这些隔离的线？

第二个问题大概可以这样解决：

filtered = [line for line in list(mline1) if line.length<2]

如何解决第一个问题？

解决方法

解决方案：

from shapely.geometry import MultiLineString
from pprint import pprint
from matplotlib import pyplot
from figures import SIZE,set_limits,plot_line,plot_bounds,color_issimple
from figures import plot_coords as _plot_coords

def plot_coords(ax,ob):
    for line in ob:
        _plot_coords(ax,line,zorder=1)


def plot_lines(ax,ob):
    color = color_issimple(ob)
    for line in ob:
        plot_line(ax,color=color,alpha=0.7,zorder=2)


fig = pyplot.figure(1,figsize=SIZE,dpi=90)

# 3: line3 lines that intersecting each other
mline1 = MultiLineString([((0,0),(2,0)),((1,(1,1)),2),(3,2)),((3,1))])
ax = fig.add_subplot(121)

# append all intersecting lines,this will create duplicates for lines
# intersecting more than one line
intersection = []
for i in range(len(mline1)):
    for j in range(i + 1,len(mline1)):
        if mline1[i].intersects(mline1[j]):
            intersection.append(mline1[i])
            intersection.append(mline1[j])

# remove duplicates
uniq_intersection = []
for line in intersection:
    if not any(p.equals(line) for p in uniq_intersection):
        uniq_intersection.append(line)

uniq_intersection = MultiLineString(uniq_intersection)
plot_coords(ax,uniq_intersection)
plot_bounds(ax,uniq_intersection)
plot_lines(ax,uniq_intersection)

ax.set_title('c) intersection')
set_limits(ax,-1,4,3)

# 4: line4 filtered lines
ax = fig.add_subplot(122)
isolated = [line for line in mline1 if line not in uniq_intersection]

# filter by length
isolated_short = [line for line in isolated if line.length < 2]
filtered = [line for line in mline1 if line not in isolated_short]

filtered = MultiLineString(filtered)
plot_coords(ax,filtered)
plot_bounds(ax,filtered)
plot_lines(ax,filtered)

ax.set_title('d) filtered')
set_limits(ax,3)

pyplot.show()

python shapely