diff --git a/bob/io/image/data/img_gray_alpha.png b/bob/io/image/data/img_gray_alpha.png
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diff --git a/bob/io/image/data/img_indexed_color_alpha.png b/bob/io/image/data/img_indexed_color_alpha.png
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diff --git a/bob/io/image/data/img_trns.png b/bob/io/image/data/img_trns.png
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diff --git a/bob/io/image/test.py b/bob/io/image/test.py
index 48fa152238deb082bd3c1a1373f4233736952a83..16cc98e04c9f64508afd3b5de3c26d8703ee15b9 100644
--- a/bob/io/image/test.py
+++ b/bob/io/image/test.py
@@ -14,26 +14,48 @@ from bob.io.base import load, write, test_utils
 
 # These are some global parameters for the test.
 PNG_INDEXED_COLOR = test_utils.datafile('img_indexed_color.png', __name__)
+PNG_INDEXED_COLOR_ALPHA = test_utils.datafile('img_indexed_color_alpha.png', __name__)
 PNG_RGBA_COLOR = test_utils.datafile('img_rgba_color.png', __name__)
+PNG_GRAY_ALPHA = test_utils.datafile('img_gray_alpha.png', __name__)
+PNG_tRNS = test_utils.datafile('img_trns.png', __name__)
 
 
 def test_png_indexed_color():
-
   # Read an indexed color PNG image, and compared with hardcoded values
   img = load(PNG_INDEXED_COLOR)
   assert img.shape == (3, 22, 32)
   assert img[0, 0, 0] == 255
   assert img[0, 17, 17] == 117
 
-
 def test_png_rgba_color():
-
   # Read an indexed color PNG image, and compared with hardcoded values
   img = load(PNG_RGBA_COLOR)
   assert img.shape == (3, 22, 32)
   assert img[0, 0, 0] == 255
   assert img[0, 17, 17] == 117
 
+def test_png_indexed_color_alpha():
+  # Read an indexed color+alpha PNG image, and compared with hardcoded values
+  img = load(PNG_INDEXED_COLOR_ALPHA)
+  assert img.shape == (3,22,32)
+  assert img[0,0,0] == 255
+  assert img[0,17,17] == 117
+
+def test_png_indexed_trns():
+  # Read an tRNS PNG image (without alpha), and compared with hardcoded values
+  img = load(PNG_tRNS)
+  assert img.shape == (3,22,32)
+  assert img[0,0,0] == 255
+  assert img[0,17,17] == 117
+
+def test_png_gray_alpha():
+  # Read a gray+alpha PNG image, and compared with hardcoded values
+  img = load(PNG_GRAY_ALPHA)
+  assert img.shape == (22,32)
+  assert img[0,0] == 255
+  assert img[17,17] == 51
+
+
 
 def transcode(filename):