Fix some issues with compositing rgba geotiffs

CHANGELOG.md

@@ -27,7 +27,7 @@
 - Be more consistent in source class name attribute assignment ([884](../../pull/884))
 
 ### Bug Fixes
-- Fix alpha on GDAL sources with a projection that have an explicit alpha channel ([909](../../pull/909))
+- Fix alpha on GDAL sources with a projection that have an explicit alpha channel ([909](../../pull/909), [915](../../pull/915))
 
 ## 1.15.1
 

sources/gdal/large_image_source_gdal/__init__.py

@@ -279,7 +279,10 @@ def _setDefaultStyle(self):
                     bstyle['nodata'] = bandInfo.get('nodata', None)
             if not hasAlpha and self.projection:
                 style.append({
-                    'band': len(self.getBandInformation()) + 1,
+                    'band': (
+                        self._bandNumber('alpha', False)
+                        if self._bandNumber('alpha', False) is not None else
+                        (len(self.getBandInformation()) + 1)),
                     'min': 0,
                     'max': 'auto',
                     'composite': 'multiply',

test/test_source_gdal.py

@@ -580,3 +580,24 @@ def testNoData():
         imagePath, projection='EPSG:3857',
         style={'bands': [{'band': 1, 'max': 100, 'min': 5, 'nodata': 0}]})
     assert source.getThumbnail()[0]
+
+
+def testAlphaProjection():
+    testDir = os.path.dirname(os.path.realpath(__file__))
+    imagePath = os.path.join(testDir, 'test_files', 'rgba_geotiff.tiff')
+    source = large_image_source_gdal.open(
+        imagePath, projection='EPSG:3857')
+    base = source.getThumbnail(encoding='PNG')[0]
+    basenp = source.getThumbnail(format='numpy')[0]
+    assert numpy.count_nonzero(basenp[:, :, 3] == 255) > 30000
+    source = large_image_source_gdal.open(
+        imagePath, projection='EPSG:3857',
+        style={'bands': [
+            {'band': 1, 'palette': 'R'},
+            {'band': 2, 'palette': 'G'},
+            {'band': 3, 'palette': 'B'}]})
+    assert source.getThumbnail(encoding='PNG')[0] == base
+    assert not (source.getThumbnail(format='numpy')[0] - basenp).any()
+    source = large_image_source_gdal.open(
+        imagePath)
+    assert numpy.count_nonzero(source.getThumbnail(format='numpy')[0][:, :, 3] == 255) > 30000