Added some tests and a couple of icns files.

PIL/IcnsImagePlugin.py

@@ -74,7 +74,7 @@ def read_32(fobj, start_length, size):
                     "Error reading channel [%r left]" % bytesleft
                     )
             band = Image.frombuffer(
-                "L", size, b"".join(data), "raw", "L", 0, 1
+                "L", pixel_size, b"".join(data), "raw", "L", 0, 1
                 )
             im.im.putband(band.im, band_ix)
     return {"RGB": im}

Tests/test_file_icns.py

@@ -0,0 +1,42 @@
+from tester import *
+
+from PIL import Image
+
+# sample icon file
+file = "Images/pillow.icns"
+data = open(file, "rb").read()
+
+def test_sanity():
+    # Loading this icon by default should result in the largest size
+    # (512x512@2x) being loaded
+    im = Image.open(file)
+    im.load()
+    assert_equal(im.mode, "RGBA")
+    assert_equal(im.size, (1024, 1024))
+    assert_equal(im.format, "ICNS")
+
+def test_sizes():
+    # Check that we can load all of the sizes, and that the final pixel
+    # dimensions are as expected
+    im = Image.open(file)
+    for w,h,r in im.info['sizes']:
+        wr = w * r
+        hr = h * r
+        im2 = Image.open(file)
+        im2.size = (w, h, r)
+        im2.load()
+        assert_equal(im2.mode, 'RGBA')
+        assert_equal(im2.size, (wr, hr))
+
+def test_older_icon():
+    # This icon was made with Icon Composer rather than iconutil; it still
+    # uses PNG rather than JP2, however (since it was made on 10.9).
+    im = Image.open('Tests/images/pillow2.icns')
+    for w,h,r in im.info['sizes']:
+        wr = w * r
+        hr = h * r
+        im2 = Image.open('Tests/images/pillow2.icns')
+        im2.size = (w, h, r)
+        im2.load()
+        assert_equal(im2.mode, 'RGBA')
+        assert_equal(im2.size, (wr, hr))