text: import glob
  import os
  from opendm import log
  from opendm import location
  from pyproj import CRS
  
  class GCPFile:
      def __init__(self, gcp_path):
          self.gcp_path = gcp_path
          self.entries = []
          self.raw_srs = ""
          self.srs = None
          self.read()
      
      def read(self):
          if self.exists():
              with open(self.gcp_path, 'r') as f:
                  contents = f.read().strip()
      
              lines = list(map(str.strip, contents.split('\n')))
              if lines:
                  self.raw_srs = lines[0] # SRS
                  self.srs = location.parse_srs_header(self.raw_srs)
  
                  for line in lines[1:]:
                      if line != "" and line[0] != "#":
                          parts = line.split()
                          if len(parts) >= 6:
                              self.entries.append(line)                          
                          else:
                              log.ODM_WARNING("Malformed GCP line: %s" % line)
  
      def iter_entries(self):
          for entry in self.entries:
              yield self.parse_entry(entry)
      
      def parse_entry(self, entry):
          if entry:
              parts = entry.split()
              x, y, z, px, py, filename = parts[:6]
              extras = " ".join(parts[6:])
              return GCPEntry(float(x), float(y), float(z), float(px), float(py), filename, extras)
  
      def get_entry(self, n):
          if n < self.entries_count():
              return self.parse_entry(self.entries[n])
  
      def entries_count(self):
          return len(self.entries)
     
      def exists(self):
          return bool(self.gcp_path and os.path.exists(self.gcp_path))
  
      def wgs84_utm_zone(self):
          """
          Finds the UTM zone where the first point of the GCP falls into
          :return utm zone string valid for a coordinates header
          """
          if self.entries_count() > 0:
              entry = self.get_entry(0)
              longlat = CRS.from_epsg("4326")
              lon, lat = location.transform2(self.srs, longlat, entry.x, entry.y)
              utm_zone, hemisphere = location.get_utm_zone_and_hemisphere_from(lon, lat)
              return "WGS84 UTM %s%s" % (utm_zone, hemisphere)
  
      def create_utm_copy(self, gcp_file_output, filenames=None, rejected_entries=None, include_extras=True):
          """
          Creates a new GCP file from an existing GCP file
          by optionally including only filenames and reprojecting each point to 
          a UTM CRS. Rejected entries can recorded by passing a list object to 
          rejected_entries.
          """
          if os.path.exists(gcp_file_output):
              os.remove(gcp_file_output)
  
          output = [self.wgs84_utm_zone()]
          target_srs = location.parse_srs_header(output[0])
          transformer = location.transformer(self.srs, target_srs)
  
          for entry in self.iter_entries():
              if filenames is None or entry.filename in filenames:
                  entry.x, entry.y, entry.z = transformer.TransformPoint(entry.x, entry.y, entry.z)
                  if not include_extras:
                      entry.extras = ''
                  output.append(str(entry))
              elif isinstance(rejected_entries, list):
                  rejected_entries.append(entry)
  
          with open(gcp_file_output, 'w') as f:
              f.write('\n'.join(output) + '\n')
  
          return gcp_file_output
  
      def make_filtered_copy(self, gcp_file_output, images_dir, min_images=3):
          """
          Creates a new GCP file from an existing GCP file includes
          only the points that reference images existing in the images_dir directory.
          If less than min_images images are referenced, no GCP copy is created.
          :return gcp_file_output if successful, None if no output file was created.
          """
          if not self.exists() or not os.path.exists(images_dir):
              return None
          
          if os.path.exists(gcp_file_output):
              os.remove(gcp_file_output)
  
          files = list(map(os.path.basename, glob.glob(os.path.join(images_dir, "*"))))
  
          output = [self.raw_srs]
          files_found = 0
          
          for entry in self.iter_entries():
              if entry.filename in files:
                  output.append(str(entry))
                  files_found += 1
  
          if files_found >= min_images:
              with open(gcp_file_output, 'w') as f:
                  f.write('\n'.join(output) + '\n')
  
              return gcp_file_output
  
      def make_micmac_copy(self, output_dir, precisionxy=1, precisionz=1, utm_zone = None):
          """
          Convert this GCP file in a format compatible with MicMac.
          :param output_dir directory where to save the two MicMac GCP files. The directory must exist.
          :param utm_zone UTM zone to use for output coordinates (UTM string, PROJ4 or EPSG definition). 
              If one is not specified, the nearest UTM zone will be selected.
          :param precisionxy horizontal precision of GCP measurements in meters.
          :param precisionz vertical precision of GCP measurements in meters.
          """
          if not os.path.isdir(output_dir):
              raise IOError("{} does not exist.".format(output_dir))
          if not isinstance(precisionxy, float) and not isinstance(precisionxy, int):
              raise AssertionError("precisionxy must be a number")
          if not isinstance(precisionz, float) and not isinstance(precisionz, int):
              raise AssertionError("precisionz must be a number")
  
          gcp_3d_file = os.path.join(output_dir, '3d_gcp.txt')
          gcp_2d_file = os.path.join(output_dir, '2d_gcp.txt')
  
          if os.path.exists(gcp_3d_file):
              os.remove(gcp_3d_file)
          if os.path.exists(gcp_2d_file):
              os.remove(gcp_2d_file)
  
          if utm_zone is None:
              utm_zone = self.wgs84_utm_zone()
  
          target_srs = location.parse_srs_header(utm_zone)
          transformer = location.transformer(self.srs, target_srs)
  
          gcps = {}
          for entry in self.iter_entries():
              utm_x, utm_y, utm_z = transformer.TransformPoint(entry.x, entry.y, entry.z)
              k = "{} {} {}".format(utm_x, utm_y, utm_z)
              if not k in gcps:
                  gcps[k] = [entry]
              else:
                  gcps[k].append(entry)
              
  
          with open(gcp_3d_file, 'w') as f3:
              with open(gcp_2d_file, 'w') as f2:
                  gcp_n = 1
                  for k in gcps:
                      f3.write("GCP{} {} {} {}\n".format(gcp_n, k, precisionxy, precisionz))
  
                      for entry in gcps[k]:
                          f2.write("GCP{} {} {} {}\n".format(gcp_n, entry.filename, entry.px, entry.py))
                      
                      gcp_n += 1
              
          return (gcp_3d_file, gcp_2d_file)
  
  class GCPEntry:
      def __init__(self, x, y, z, px, py, filename, extras=""):
          self.x = x
          self.y = y
          self.z = z
          self.px = px
          self.py = py
          self.filename = filename
          self.extras = extras
      
      def __str__(self):
          return "{} {} {} {} {} {} {}".format(self.x, self.y, self.z, 
                                               self.px, self.py, 
                                               self.filename, 
                                               self.extras).rstrip()