BathymetryModel/parallel_offset.py at master · ssvassiliev/BathymetryModel · GitHub

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#!/usr/bin/python

import shapefile, sys, os, fiona
from shapely.geometry import Point, LineString
import matplotlib.pyplot as plt

print "\n***************** Parallel offset *****************"
# This script generates a set of polylines  parallel to all input
# polylines found in the input ESRI shapefile. The lines are generated
# at the distance offDist from the input line, inside or outside of the
# input polygons. The output is in  ESRI polyline Z format where Z is
# (constant) depth. In addition depth is also saved in the record #1 "Depth".

# Required input:
#----------------
offDist = 1.0
Depth = -0.2
WorkDir = os.getcwd()+"/"
InputFile = "Opinicon/Data/opinicon_perimeter_ed_simpl_0.4-3.shp"
#----------------
# Offset the following shapes to the right, default is offset left.
ShapesRight = [0,12,13,25,31,32,33,36,38,39,40,41,42,45,46,47,50,51,52,53,54]
#----------------
OutFile = "Opinicon/Output/opinicon_offset_ed_simpl_0.4-3."
#----------------
# If parallel offset algorithm crashes try to adjust the coordinate shifts
dX = -100
dY = -100
#---------------------------------------------------------------
InputFile = WorkDir + InputFile
OutFile = WorkDir + OutFile
print "<<< Reading perimeter >>>\n...", os.path.basename(InputFile)
# Read shoreline points
sh = shapefile.Reader(InputFile)
# Shape records
sh_records = sh.shapeRecords()
# Shapes:
sh_shapes = sh.shapes()

# Make temporary coordinates (perimeter + islands) and
# an array of pointers [ind] to starting points of the records
xt=[];yt=[];zt=[];
nShapes=range(0,len(sh_shapes))

j=0; ii=0; ind=[0]
shiftX=sh_shapes[0].points[0][0]
shiftY=sh_shapes[0].points[0][1]

for i in nShapes:
   n=len(sh_shapes[j].points)
   ii=ii+n
   ind.append(ii)
   j+=1
   for k in range(0,n):
       xt.append(sh_shapes[i].points[k][0] - shiftX + dX)
       yt.append(sh_shapes[i].points[k][1] - shiftY + dY)
       zt.append(0.0)

# Perimeter parallel offset line
#----------------------------------------------------------------------------
# all shapes, left offset is 1, right is 0
print "<<< Generating parallel offset lines >>>"
Shapes=[]
for i in range(0,len(sh_records)):
  Shapes.append(1)
for i in ShapesRight:
  Shapes[i]=0

# Initialize output shapefile
ShapeType=shapefile.POLYLINEZ
w=shapefile.Writer(ShapeType)
w.autobalance=1
w.field("Depth", "F",10,5)

# Compute offset for the following records
#-----------------------------------------
dist=0
for j in range(len(sh_records)):
  xf=[]; yf=[]; p=[]
# prepare shapely polyline from the list of coordinates
  for i in range(ind[j],ind[j+1]):
       p.append(Point(xt[i],yt[i]))
       xf.append(xt[i]); yf.append(yt[i])
  line=LineString(p)
  dist += line.length
# generate parallel offset. 1 - interior offset; 0 - exterior offset
  if Shapes[j] == 1:
    try:
       offsetLine = line.parallel_offset(distance=offDist, side='left', join_style=2, mitre_limit=5.0)
    except ValueError:
       sys.exit("Bug in parallel offset, try different dX/dY")
  else:
    try:
       offsetLine = line.parallel_offset(distance=offDist, side='right', join_style=2, mitre_limit=5.0)
    except ValueError:
       sys.exit("Bug in parallel offset, try different dX/dY ")

  try:
  # try to process offset line as a list of polylines
    print  "S" + str(j),
    for i in range(len(list(offsetLine))):
       vertex=[]
       x1off,y1off=offsetLine[i].xy
       for k in range(0,len(x1off)):
          vertex.append([x1off[k] + shiftX - dX, y1off[k] + shiftY - dY, Depth])
       print len(x1off),"|",
       w.record(Depth)
       w.poly([vertex])
       plt.plot(x1off,y1off,c='r')

  except TypeError:
  # if multiline reader fails process offsetLine as a single line
    vertex=[]
    x1off,y1off=offsetLine.xy
    print len(x1off),"|",
    for k in range(0, len(x1off)):
       vertex.append([x1off[k] + shiftX - dX, y1off[k] + shiftY - dY, Depth])
    w.record(Depth)
    w.poly([vertex])
    plt.plot(x1off,y1off,c='r')

  plt.plot(xf,yf,c='lightgrey')
#  print ""
  sys.stdout.flush()

print "\n<<< Writing perimeter offset >>>\n...", os.path.basename(OutFile)+'shp'
print "... perimeter including islands =",dist,"m"
for s in w.shapes():
  s.shapeType = ShapeType
w.save(OutFile)

# write projection
with fiona.open(InputFile) as fp:
 prj=open(OutFile+"prj","w")
 prj.write(fp.crs_wkt)
 prj.close()

# plot results
# plt.show()