Add RPC projection class

gaia/geo/__init__.py

@@ -2,3 +2,4 @@
 from gaia.geo.processes_raster import *
 from gaia.geo.processes_vector import *
 from gaia.geo.geo_inputs import *
+from gaia.geo.rpc import *

gaia/geo/rpc.py

@@ -0,0 +1,124 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+###############################################################################
+#  Copyright 2017 by Kitware Inc.
+#
+#  Licensed under the Apache License, Version 2.0 ( the "License" );
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+###############################################################################
+"""Model RPC (Rational Polynomial Camera) projections
+"""
+
+import numpy
+
+
+class RPC_Model(object):
+    """Represents a Rational Polynomial Camera (RPC) model
+    """
+
+    def __init__(self):
+        """Constructor from a GDAL RPC dictionary
+        """
+        # This constructs something like an identity camera
+        # (Lon, Lat, Alt) ==> (Lon, Lat)
+        dtype = 'float64'
+        self.coeff = numpy.zeros((4,20), dtype=dtype)
+        self.coeff[0,1] = 1
+        self.coeff[2,2] = 1
+        self.world_offset = numpy.zeros((1,3), dtype=dtype)
+        self.world_scale = numpy.ones((1,3), dtype=dtype)
+        self.image_offset = numpy.zeros((1,2), dtype=dtype)
+        self.image_scale = numpy.ones((1,2), dtype=dtype)
+
+    @staticmethod
+    def power_vector(point):
+        """Compute the vector of polynomial terms
+        """
+        x,y,z = point
+        xx = x * x
+        xy = x * y
+        xz = x * z
+        yy = y * y
+        yz = y * z
+        zz = z * z
+        xxx = xx * x
+        xxy = xx * y
+        xxz = xx * z
+        xyy = xy * y
+        xyz = xy * z
+        xzz = xz * z
+        yyy = yy * y
+        yyz = yy * z
+        yzz = yz * z
+        zzz = zz * z
+        # This is the standard order of terms used in NITF metadata
+        return numpy.array([1, x, y, z, xy, xz, yz, xx, yy, zz, xyz, xxx, xyy, xzz, xxy, yyy, yzz, xxz, yyz, zzz])
+
+    def project(self, point):
+        """Project a long, lat, alt point into image coordinates
+        """
+        norm_pt = (numpy.array(point) - self.world_offset) / self.world_scale
+        polys = numpy.dot(self.coeff, self.power_vector( norm_pt ))
+        img_pt = numpy.array([polys[0] / polys[1], polys[2] / polys[3]])
+        return img_pt * self.image_scale + self.image_offset
+
+
+def rpc_from_gdal_dict(md_dict):
+    """Construct a RPC_Model from a GDAL RPC meta-data dictionary
+
+    The format of the dictionary matches what GDAL returns and contains
+    the standard fields from the RPC00B standard
+    """
+    def data_from_keys(keys):
+        """Extract from the data dictionary by list of keys"""
+        if keys in md_dict:
+            return numpy.array(md_dict[keys].split(), dtype='float64')
+        if all (k in md_dict for k in keys):
+            return numpy.array([md_dict[k] for k in keys], dtype='float64')
+        raise KeyError("Unable to find "+str(keys)+" in the dictionary")
+
+    rpc = RPC_Model()
+    rpc.world_offset = data_from_keys(('LONG_OFF', 'LAT_OFF', 'HEIGHT_OFF'))
+    rpc.world_scale = data_from_keys(('LONG_SCALE', 'LAT_SCALE', 'HEIGHT_SCALE'))
+    rpc.image_offset = data_from_keys(('SAMP_OFF', 'LINE_OFF'))
+    rpc.image_scale = data_from_keys(('SAMP_SCALE', 'LINE_SCALE'))
+    rpc.coeff[0,:] = data_from_keys('SAMP_NUM_COEFF')
+    rpc.coeff[1,:] = data_from_keys('SAMP_DEN_COEFF')
+    rpc.coeff[2,:] = data_from_keys('LINE_NUM_COEFF')
+    rpc.coeff[3,:] = data_from_keys('LINE_DEN_COEFF')
+    return rpc
+
+
+def rpc_to_gdal_dict(rpc, precision=12):
+    """Construct a GDAL RPC meta-data dictionary from a RPC_Model
+
+    The format of the dictionary matches what GDAL returns and contains
+    the standard fields from the RPC00B standard
+    """
+    md_dict = dict()
+    fmt = '%0.' + str(int(precision)) + 'f'
+    md_dict['LONG_OFF']       = fmt % rpc.world_offset[0]
+    md_dict['LAT_OFF']        = fmt % rpc.world_offset[1]
+    md_dict['HEIGHT_OFF']     = fmt % rpc.world_offset[2]
+    md_dict['LONG_SCALE']     = fmt % rpc.world_scale[0]
+    md_dict['LAT_SCALE']      = fmt % rpc.world_scale[1]
+    md_dict['HEIGHT_SCALE']   = fmt % rpc.world_scale[2]
+    md_dict['SAMP_OFF']       = fmt % rpc.image_offset[0]
+    md_dict['LINE_OFF']       = fmt % rpc.image_offset[1]
+    md_dict['SAMP_SCALE']     = fmt % rpc.image_scale[0]
+    md_dict['LINE_SCALE']     = fmt % rpc.image_scale[1]
+    md_dict['SAMP_NUM_COEFF'] = ' '.join(fmt % c for c in rpc.coeff[0,:])
+    md_dict['SAMP_DEN_COEFF'] = ' '.join(fmt % c for c in rpc.coeff[1,:])
+    md_dict['LINE_NUM_COEFF'] = ' '.join(fmt % c for c in rpc.coeff[2,:])
+    md_dict['LINE_DEN_COEFF'] = ' '.join(fmt % c for c in rpc.coeff[3,:])
+    return md_dict