Merge pull request #69 from ioam/project_ops

Added project_points and general project operation

geoviews/__init__.py

@@ -9,6 +9,7 @@
 from .element import (_Element, Feature, Tiles,     # noqa (API import)
                       WMTS, LineContours, FilledContours, Text, Image,
                       Points, Path, Polygons, Shape, Dataset)
+from . import operation                             # noqa (API import)
 from . import plotting                              # noqa (API import)
 from . import feature                               # noqa (API import)
 

geoviews/operation.py

@@ -1,11 +1,11 @@
 import param
 import numpy as np
 from cartopy import crs as ccrs
-from cartopy.img_transform import regrid
+from cartopy.img_transform import warp_array
 
 from holoviews.operation import ElementOperation
 
-from .element import Image, Shape, Polygons, Path
+from .element import Image, Shape, Polygons, Path, Points
 from .util import project_extents
 
 class project_shape(ElementOperation):
@@ -19,13 +19,38 @@ class project_shape(ElementOperation):
                                      instantiate=False, doc="""
         Projection the shape type is projected to.""")
 
+    supported_types = [Shape, Polygons, Path]
+
     def _process_element(self, element):
         geom = self.p.projection.project_geometry(element.geom(),
                                                   element.crs)
         return element.clone(geom, crs=self.p.projection)
 
     def _process(self, element, key=None):
-        return element.map(self._process_element, [Shape, Polygons, Path])
+        return element.map(self._process_element, self.supported_types)
+
+
+class project_points(ElementOperation):
+
+    projection = param.ClassSelector(default=ccrs.GOOGLE_MERCATOR,
+                                     class_=ccrs.Projection,
+                                     instantiate=False, doc="""
+        Projection the shape type is projected to.""")
+
+    supported_types = [Points]
+
+    def _process_element(self, element):
+        xdim, ydim = element.dimensions()[:2]
+        xs, ys = (element.dimension_values(i) for i in range(2))
+        coordinates = self.p.projection.transform_points(element.crs, xs, ys)
+        new_data = element.columns()
+        new_data[xdim.name] = coordinates[:, 0]
+        new_data[ydim.name] = coordinates[:, 1]
+        return element.clone(new_data, crs=self.p.projection,
+                             datatype=[element.interface.datatype]+element.datatype)
+
+    def _process(self, element, key=None):
+        return element.map(self._process_element, self.supported_types)
 
 
 class project_image(ElementOperation):
@@ -41,23 +66,38 @@ class project_image(ElementOperation):
                                      instantiate=False, doc="""
         Projection the image type is projected to.""")
 
+    supported_types = [Image]
+
     def _process(self, img, key=None):
         proj = self.p.projection
         if proj == img.crs:
             return img
-        arr = img.dimension_values(2, flat=False).T
-        xs = img.dimension_values(0)
-        ys = img.dimension_values(1)
+        arr = img.dimension_values(2, flat=False)
         x0, x1 = img.range(0)
         y0, y1 = img.range(1)
         xn, yn = arr.shape
         px0, py0, px1, py1 = project_extents((x0, y0, x1, y1),
                                              img.crs, proj)
-        px = np.linspace(px0, px1, xn)
-        py = np.linspace(py0, py1, yn)
-        pxs, pys = np.meshgrid(px, py)
-        pxs = pxs.reshape((yn, xn))
-        pys = pys.reshape((yn, xn))
-        parray = regrid(arr, xs, ys, img.crs, proj, pxs, pys)
-        return Image((px, py, parray), kdims=img.kdims,
+        src_ext, trgt_ext = (x0, x1, y0, y1), (px0, px1, py0, py1)
+        projected, extents = warp_array(arr, proj, img.crs, (xn, yn),
+                                        src_ext, trgt_ext)
+        bounds = (extents[0], extents[2], extents[1], extents[3])
+        data = np.flipud(projected)
+        return Image(data, bounds=bounds, kdims=img.kdims,
                      vdims=img.vdims, crs=proj)
+
+
+class project(ElementOperation):
+    """
+    Projects GeoViews Element types to the specified projection.
+    """
+
+    projection = param.ClassSelector(default=ccrs.GOOGLE_MERCATOR,
+                                     class_=ccrs.Projection,
+                                     instantiate=False, doc="""
+        Projection the image type is projected to.""")
+
+    def _process(self, element, key=None):
+        element = element.map(project_image, project_image.supported_types)
+        element = element.map(project_shape, project_shape.supported_types)
+        return element.map(project_points, project_points.supported_types)

geoviews/util.py

@@ -38,11 +38,11 @@ def project_extents(extents, src_proj, dest_proj, tol=1e-6):
     domain_in_src_proj = Polygon([[x1, y1], [x2, y1],
                                   [x2, y2], [x1, y2],
                                   [x1, y1]])
-    boundary_poly = Polygon(dest_proj.boundary)
+    boundary_poly = Polygon(src_proj.boundary)
     if src_proj != dest_proj:
         # Erode boundary by threshold to avoid transform issues.
         # This is a workaround for numerical issues at the boundary.
-        eroded_boundary = boundary_poly.buffer(-dest_proj.threshold)
+        eroded_boundary = boundary_poly.buffer(-src_proj.threshold)
         geom_in_src_proj = eroded_boundary.intersection(
             domain_in_src_proj)
         geom_in_crs = dest_proj.project_geometry(geom_in_src_proj, src_proj)