頂点列で表すPolygonを構成する長いエッジに対しエッジ分割し、頂点を追加する。

頂点列で表すPolygon図形を構成するエッジのうち、任意の長さ以上のエッジに対して分割し頂点を増やす処理。

Process of dividing vertices of arbitrary length and increasing vertex among edges constituting Polygon figure represented by vertex sequence.

(results sample picture)
@red points : Polygon points
@blue pattern : Filled polygon
before

after

(results split edge)
original_points
[[237.894 0. ]
[130.554 105.408]
[ 43.748 0.626]
[ 0. 42.589]
[129.559 189. ]
[280. 42.589]
[237.894 0. ]]

after split points
[[237.894 0. ]
[184.224 52.704 ]
[130.554 105.408 ]
[ 87.151 53.017 ]
[ 43.748 0.626 ]
[ 0. 42.589 ]
[ 64.7795 115.7945 ]
[129.559 189. ]
[179.706 140.19633333]
[229.853 91.39266667]
[280. 42.589 ]
[237.894 0. ]]

sample code

import cv2
import sys
import math
import numpy as np

def calc_vabs(v):
  x1 = v[0]
  y1 = v[1]
  x2 = v[2]
  y2 = v[3]

  xx = x2 - x1
  yy = y2 - y1
  xxyy = xx*xx + yy*yy
  dist = math.sqrt(xxyy)
  return dist

def split_vect(v,slen):
  tp = np.empty((0,2), float)
  dist = calc_vabs(v)
  if dist < slen:
    x1 = v[0]
    y1 = v[1]
    tp = np.append(tp, np.array([[x1,y1]]), axis=0)

  else:
    snum = int(math.ceil(dist/slen))
    x1 = v[0]
    y1 = v[1]
    x2 = v[2]
    y2 = v[3]
    xx = x2 - x1
    yy = y2 - y1
    dx = xx/snum
    dy = yy/snum

    for i in range(snum):
      xx = x1 + dx * i
      yy = y1 + dy * i
      tp = np.append(tp, np.array([[xx,yy]]), axis=0)

  return tp

def split_longedge(oarr, slen):
  """
  if 2points distance is long than slen,
  make new point between 2points.
  return new point list.
  """

  # -----------------------------------
  # convert point list to vector list
  # -----------------------------------
  varr = np.empty((0,4), float)
  for i in range(len(lines)):
    lines[i].strip()
    jj = lines[i].split()
    xx1 = float(jj[0])
    yy1 = float(jj[1])

    if i != len(lines) -1:
      lines[i+1].strip()
      jj = lines[i+1].split()
      xx2 = float(jj[0])
      yy2 = float(jj[1])
    else:
      break

    varr = np.append(varr, np.array([[xx1,yy1,xx2,yy2]]), axis=0)
    i = i + 1

  # -----------------------------------
  # split long vector, and convert vector list to point list
  # -----------------------------------
  arr = np.empty((0,2),float)
  for p in varr:
    tp = split_vect(p,slen)
    arr = np.append(arr, tp, axis=0)

  arr0 = np.array([[arr[0][0], arr[0][1]]])
  arr = np.append(arr, arr0, axis=0)

  return arr

def output2picture(arr, pic_name):
  w = 200 
  h = 300
  img = np.zeros((w, h, 3), np.uint8)

  arr0 = np.empty((0,2), int)
  for p in arr:
    xx = int(p[0])
    yy = int(p[1])
    arr0 = np.append(arr0, np.array([[xx,yy]]), axis=0)
  cv2.fillPoly(img, [arr0], (255, 60, 60))

  for p in arr:
    nnn = np.array([int(p[0]), int(p[1])])
    cv2.drawMarker(img, tuple(nnn), (0, 0, 255), thickness=2)
  cv2.imwrite(pic_name, img)


if __name__ == '__main__':

  in_data = open("./polygon_points.txt")
  lines = in_data.readlines()
  oarr = np.empty((0,2), float)
  for i in range(len(lines)):
    lines[i].strip()
    jj = lines[i].split()
    xx = float(jj[0])
    yy = float(jj[1])
    oarr = np.append(oarr, np.array([[xx,yy]]), axis=0)
    i = i + 1

  arr = np.empty((0,2),float)

  #-------------------------------------------------
  # split function.second argument is split length.
  arr = split_longedge(oarr,100)
  #-------------------------------------------------


  print("\noriginal_points\n",oarr)
  print("\nafter split points\n",arr)
  output2picture(oarr,"01_original_points.png")
  output2picture(arr ,"02_split_points.png")

■polygon_points.txt
237.894 0.000
130.554 105.408
43.748 0.626
0.000 42.589
129.559 189.000
280.000 42.589
237.894 0.000