add make terrain sample data function (#439)

* add make terrain sample data function

* add noise requirement

* add noise requirement

* add noise requirement

* change noise to be an optional requirement

* move make terrain function inside datasets module init

Author: giancastro

requirements.txt

@@ -1,3 +1,4 @@
 datashader
 xarray
 bokeh>2
+noise >=1.2.2

setup.py

@@ -27,7 +27,7 @@
     'pyct <=0.4.6',
     'param >=1.6.1',
     'distributed >=2021.03.0',
-    'spatialpandas'
+    'spatialpandas',
 ]
 
 examples = [
@@ -37,6 +37,7 @@
 extras_require = {
     'tests': [
         'pytest',
+        'noise >=1.2.2',
     ],
     'examples': examples,
 }

xrspatial/datasets/__init__.py

@@ -1,8 +1,18 @@
 import os
+
+import dask.array as da
+import datashader as ds
+import noise
+import numpy as np
+import pandas as pd
 import xarray as xr
 
 
-__all__ = ["available", "get_data"]
+__all__ = [
+    'available',
+    'get_data',
+    'make_terrain',
+]
 
 _module_path = os.path.dirname(os.path.abspath(__file__))
 _available_datasets = [p for p in next(os.walk(_module_path))[1]
@@ -34,3 +44,77 @@ def get_data(dataset):
         msg += f'Available folders are {available_datasets}.'
         raise ValueError(msg)
     return data
+
+
+def make_terrain(
+    shape=(1024, 1024),
+    scale=100.0,
+    octaves=6,
+    persistence=0.5,
+    lacunarity=2.0,
+    chunks=(512, 512)
+):
+    """
+    Generate a pseudo-random terrain data dask array.
+
+    Parameters
+    ----------
+    shape : int or tuple of int, default=(1024, 1024)
+        Output array shape.
+    scale : float, default=100.0
+        Noise factor scale.
+    octaves : int, default=6
+        Number of waves when generating the noise.
+    persistence : float, default=0.5
+        Amplitude of each successive octave relative.
+    lacunarity : float, default=2.0
+        Frequency of each successive octave relative.
+    chunks : int or tuple of int, default=(512, 512)
+        Number of samples on each block.
+
+    Returns
+    -------
+    terrain : xarray.DataArray
+        2D array of generated terrain values.
+    """
+    def _func(arr, block_id=None):
+        block_ystart = block_id[0] * arr.shape[0]
+        block_xstart = block_id[1] * arr.shape[1]
+        out = np.zeros(arr.shape)
+        for i in range(out.shape[0]):
+            for j in range(out.shape[1]):
+                out[i][j] = noise.pnoise2(
+                    (block_ystart + i)/scale,
+                    (block_xstart + j)/scale,
+                    octaves=octaves,
+                    persistence=persistence,
+                    lacunarity=lacunarity,
+                    repeatx=1024,
+                    repeaty=1024,
+                    base=42,
+                )
+        return out
+
+    data = (
+        da.zeros(shape=shape, chunks=chunks, dtype=np.float32)
+        .map_blocks(_func, dtype=np.float32)
+    )
+
+    cvs = ds.Canvas(
+        x_range=(0, 500),
+        y_range=(0, 500),
+        plot_width=shape[1],
+        plot_height=shape[0],
+    )
+
+    hack_agg = cvs.points(pd.DataFrame({'x': [], 'y': []}), 'x', 'y')
+
+    agg = xr.DataArray(
+        data,
+        name='terrain',
+        coords=hack_agg.coords,
+        dims=hack_agg.dims,
+        attrs={'res': 1},
+    )
+
+    return agg

xrspatial/tests/test_datasets.py

@@ -0,0 +1,11 @@
+import dask.array as da
+import xarray as xr
+
+from xrspatial.datasets import make_terrain
+
+
+def test_make_terrain():
+    terrain = make_terrain()
+    assert terrain is not None
+    assert isinstance(terrain, xr.DataArray)
+    assert isinstance(terrain.data, da.Array)