add img_encode utility function

mapboxgl/utils.py

@@ -1,5 +1,11 @@
+import json
+import base64
+from io import BytesIO
+
+from matplotlib.image import imsave
+
 from .colors import color_ramps
-import geojson, json, re
+import geojson
 from colour import Color
 
 
@@ -147,3 +153,20 @@ def create_color_stops(breaks, colors='RdYlGn', color_ramps=color_ramps):
                 stops.append([b, ramp[i]])
 
     return stops
+
+
+def img_encode(arr, **kwargs):
+    """Encode ndarray to base64 string image data
+
+    Parameters
+    ----------
+    arr: ndarray (rows, cols, depth)
+    kwargs: passed directly to matplotlib.image.imsave
+    """
+    sio = BytesIO()
+    imsave(sio, arr, **kwargs)
+    sio.seek(0)
+    img_format = kwargs['format'] if kwargs.get('format') else 'png'
+    img_str = base64.b64encode(sio.getvalue()).decode()
+
+    return 'data:image/{};base64,{}'.format(img_format, img_str)

mapboxgl/viz.py

@@ -289,7 +289,7 @@ def __init__(self,
                  **kwargs):
         """Construct a Mapviz object
 
-        :param coordinates: property to determine image coordinates.
+        :param coordinates: property to determine image coordinates (UL, UR, LR, LL).
             EX. [[-80.425, 46.437], [-71.516, 46.437], [-71.516, 37.936], [-80.425, 37.936]]
         :param image: image url or base64 encoded.  EX. "https://www.mapbox.com/mapbox-gl-js/assets/radar.gif"]
 

setup.py

@@ -31,6 +31,6 @@
         'mapboxgl': ['templates/*']},
     include_package_data=True,
     zip_safe=False,
-    install_requires=['jinja2', 'geojson', 'colour'],
+    install_requires=['jinja2', 'geojson', 'colour', 'matplotlib'],
     extras_require={
         'test': ['pytest', 'pytest-cov', 'codecov', 'mock', 'jupyter', 'Sphinx', 'pandas']})