Fix alpha-blending on Unicorn HAT HD device

rm-hull · May 26, 2019 · 8e847e8 · 8e847e8
1 parent 0adf502
commit 8e847e8
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Showing 4 changed files with 28 additions and 1 deletion.
diff --git a/CHANGES.rst b/CHANGES.rst
@@ -4,6 +4,8 @@ ChangeLog
 +------------+------------------------------------------------------------------------+------------+
 | Version    | Description                                                            | Date       |
 +============+========================================================================+============+
+| *upcoming* | * Fix alpha-channel blending for Unicorn Hat HD display                | TBC        |
++------------+------------------------------------------------------------------------+------------+
 | **1.3.0**  | * Add support for Pimoroni's Unicorn Hat HD                            | 2019/05/26 |
 +------------+------------------------------------------------------------------------+------------+
 | **1.2.0**  | * Add option to control if 8x8 blocks are arranged in reverse order    | 2019/04/20 |

diff --git a/luma/led_matrix/device.py b/luma/led_matrix/device.py
@@ -585,7 +585,7 @@ def display(self, image):
 
         for idx, (r, g, b, a) in enumerate(image.getdata()):
             offset = idx * 3
-            brightness = int(a / 255.0) if a != 0xFF else normalized_brightness
+            brightness = a / 255.0 if a != 255 else normalized_brightness
             buf[offset] = int(r * brightness)
             buf[offset + 1] = int(g * brightness)
             buf[offset + 2] = int(b * brightness)

diff --git a/tests/reference/data/demo_unicornhathd_alphablend.json b/tests/reference/data/demo_unicornhathd_alphablend.json
@@ -0,0 +1,17 @@
+[
+    32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8,
+    32, 16, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8, 32, 16, 8
+]
diff --git a/tests/test_unicornhathd.py b/tests/test_unicornhathd.py
@@ -50,3 +50,11 @@ def test_display():
     with canvas(device) as draw:
         draw.rectangle(device.bounding_box, outline="white")
     serial.data.assert_called_once_with([0x72] + get_json_data('demo_unicornhathd'))
+
+
+def test_alpha_blending():
+    device = unicornhathd(serial)
+    serial.reset_mock()
+    with canvas(device) as draw:
+        draw.rectangle(device.bounding_box, outline=(255, 128, 64, 32))
+    serial.data.assert_called_once_with([0x72] + get_json_data('demo_unicornhathd_alphablend'))