docs(python): add example_coordinate_transform.py

Fixes #517.

python/examples/example_coordinate_transform.py

@@ -0,0 +1,45 @@
+import argparse
+
+import neuroglancer
+import neuroglancer.cli
+import numpy as np
+
+if __name__ == "__main__":
+    ap = argparse.ArgumentParser()
+    neuroglancer.cli.add_server_arguments(ap)
+    args = ap.parse_args()
+    neuroglancer.cli.handle_server_arguments(args)
+    viewer = neuroglancer.Viewer()
+
+    ix, iy, iz = np.meshgrid(
+        *[np.linspace(0, 1, n) for n in [100, 100, 100]], indexing="ij"
+    )
+    data = np.cast[np.uint32](
+        np.floor(np.sqrt((ix - 0.5) ** 2 + (iy - 0.5) ** 2 + (iz - 0.5) ** 2) * 10)
+    )
+    data = np.pad(data, 1, "constant")
+    dimensions = neuroglancer.CoordinateSpace(
+        names=["x", "y", "z"], units="nm", scales=[10, 10, 10]
+    )
+
+    with viewer.txn() as s:
+        s.dimensions = dimensions
+        s.layers["original"] = neuroglancer.SegmentationLayer(
+            source=[
+                neuroglancer.LayerDataSource(
+                    neuroglancer.LocalVolume(data=data, dimensions=dimensions)
+                )
+            ],
+        )
+        s.layers["transformed"] = neuroglancer.SegmentationLayer(
+            source=[
+                neuroglancer.LayerDataSource(
+                    neuroglancer.LocalVolume(data=data, dimensions=dimensions),
+                    transform=neuroglancer.CoordinateSpaceTransform(
+                        output_dimensions=dimensions,
+                        matrix=[[1, 0, 0, 0], [1, 1, 0, 0], [0, 0, 1, 0]],
+                    ),
+                )
+            ],
+        )
+    print(viewer)