Implement a measure of similarity for two bool arrays and use it to measure

how close we are getting to encoding the target image.

main.py

@@ -8,7 +8,7 @@ import screen
 CYCLES = 1024 * 1024
 MAX_OUT = 20 * 1024
 VIDEO_FPS = 30
-APPLE_FPS = 10
+APPLE_FPS = 5
 
 
 def main():
@@ -25,6 +25,7 @@ def main():
             im = Image.fromarray(frame)
             im = im.resize((screen.Frame.XMAX, screen.Frame.YMAX))
             im = im.convert("1")
+            im = np.array(im)
             # im.show()
 
             f = screen.Frame(im)
@@ -34,18 +35,18 @@ def main():
             decoder.from_stream(iter(stream))
             assert np.array_equal(decoder.screen, s.screen)
 
-            #print(" ".join("%02x(%02d)" % (b, b) for b in stream))
+            # print(" ".join("%02x(%02d)" % (b, b) for b in stream))
             # assert that the screen decodes to the original bitmap
-            #bm = s.to_bitmap()
+            bm = s.to_bitmap()
+
             #           print(np.array(im)[0:5,0:5])
             #            print(bm[0:5,0:5])
 
-
-            #print("Comparing bitmaps")
-            #print(np.array(im))
-            #print(bm)
-            #print(s.screen)
-            #assert np.array_equal(bm, im), np.ma.masked_array(
+            # print("Comparing bitmaps")
+            # print(np.array(im))
+            # print(bm)
+            # print(s.screen)
+            # assert np.array_equal(bm, im), np.ma.masked_array(
             #    bm, np.logical_not(np.logical_xor(bm, im)))
 
             # d = Image.fromarray(s.screen)
@@ -55,7 +56,8 @@ def main():
             if bytes_out > MAX_OUT:
                 break
 
-            print("Frame %d, %d bytes" % (idx, len(stream)))
+            print("Frame %d, %d bytes, similarity = %f" % (
+                idx, len(stream), s.similarity(im,bm)))
             out.write(stream)
 
         out.write(bytes(s.done()))

screen.py

@@ -169,6 +169,13 @@ class Screen:
         cycles_per_pixel = cycles / xor_weight
         return cycles_per_pixel
 
+    @staticmethod
+    def similarity(a1: np.array, a2: np.array) -> float:
+        """Measure bitwise % similarity between two arrays"""
+        bits_different = np.sum(np.logical_xor(a1, a2))
+
+        return 1 - (bits_different / (np.shape(a1)[0] * np.shape(a1)[1]))
+
     def encoded_byte_stream(self, deltas: np.array,
                             target: np.array) -> Iterator[int]:
         """Emit encoded byte stream for rendering the image.
@@ -201,6 +208,9 @@ class Screen:
         page = 0x20
         content = 0x7f
 
+        # TODO: strictly picking the highest next score might end up
+        #  thrashing around between pages/content bytes.  Maybe score over
+        #  larger runs of bytes?
         scores = []
         while changes:
             if not scores:
@@ -227,7 +237,7 @@ class Screen:
 
                 # Invalidate scores
                 # TODO: we don't need to invalidate all of them, just those
-                #  for the current page
+                #  for the old and new page
                 scores = []
 
             if new_content != content:
@@ -237,7 +247,7 @@ class Screen:
 
                 # Invalidate scores
                 # TODO: we don't need to invalidate all of them, just those
-                #  for the current page
+                #  for the old and new content byte
                 scores = []
 
             self._write(page << 8 | offset, content)