add test for #997- closes #997

tests/data/good_maps/raster-alpha-gradient.xml

@@ -1,15 +1,15 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!DOCTYPE Map[]>
-<Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" background-color="transparent">
+<Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" background-color="blue">
 
-<Style name="white" filter-mode="first">
+<Style name="transp">
   <Rule>
     <RasterSymbolizer opacity="1" scaling="bilinear" />
   </Rule>
 </Style>
-<Layer name="white"
+<Layer name="transp"
   srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over">
-    <StyleName>white</StyleName>
+    <StyleName>transp</StyleName>
     <Datasource>
        <Parameter name="file">../raster/transp.tiff</Parameter>
        <Parameter name="type">gdal</Parameter>

tests/data/good_maps/raster-alpha.xml

@@ -2,7 +2,7 @@
 <!DOCTYPE Map[]>
 <Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" background-color="red">
 
-<Style name="white" filter-mode="first">
+<Style name="white">
   <Rule>
     <RasterSymbolizer opacity="1" scaling="bilinear" />
   </Rule>

tests/python_tests/raster_alpha_test.py

@@ -23,6 +23,18 @@ def test_map_alpha_compare():
     expected_im = mapnik.Image.open(expected)
     eq_(im.tostring(),expected_im.tostring(), 'failed comparing actual (%s) and expected(%s)' % (actual,'tests/python_tests/'+ expected))
 
+def test_map_alpha_gradient_compare():
+    m = mapnik.Map(600,400)
+    mapnik.load_map(m,'../data/good_maps/raster-alpha-gradient.xml')
+    m.zoom_all()
+    actual = '/tmp/mapnik-raster-alpha-gradient.png'
+    expected = 'images/support/raster-alpha-gradient.png'
+    im = mapnik.Image(m.width,m.height)
+    mapnik.render(m,im)
+    im.save(actual)
+    expected_im = mapnik.Image.open(expected)
+    eq_(im.tostring(),expected_im.tostring(), 'failed comparing actual (%s) and expected(%s)' % (actual,'tests/python_tests/'+ expected))
+
 
 if __name__ == "__main__":
     setup()