adding inline image_overlay test

Author: andrewgiessel

tests/folium_tests.py

@@ -484,10 +484,14 @@ def test_fit_bounds(self):
     def test_image_overlay(self):
         """Test image overlay"""
         from numpy.random import random
-        import imageio
+        from folium.utilities import write_png
+        import base64
 
         data = random((100,100))
-        imageio.imwrite('test.png', data)
+        png_str = write_png(data)
+        with open('data.png', 'wb') as f:
+            f.write(png_str)
+        inline_image_url = "data:image/png;base64,"+base64.b64encode(png_str)
 
         image_tpl = self.env.get_template('image_layer.js')
         image_name = 'Image_Overlay'
@@ -502,8 +506,17 @@ def test_image_overlay(self):
                                            'image_opacity': image_opacity
         })
 
-        self.map.image_overlay(data)
+        self.map.image_overlay(data, filename=image_url)
+        assert image_rendered in self.map.template_vars['image_layers']
+
 
+        image_rendered = image_tpl.render({'image_name': image_name,
+                                           'image_url': inline_image_url,
+                                           'image_bounds': image_bounds,
+                                           'image_opacity': image_opacity
+        })
+
+        self.map.image_overlay(data)
         assert image_rendered in self.map.template_vars['image_layers']
-        
+