Tidy

image.py

@@ -1,6 +1,5 @@
 """Image transformation functions."""
 
-import colour
 import numpy as np
 from PIL import Image
 

palette.py

@@ -25,11 +25,31 @@ class Palette:
                 self.CAM16UCS[k] = colour.convert(
                     v / 255, "sRGB", "CAM16UCS").astype(np.float32)
 
-    def pixels_to_idx(self, pixels: np.array) -> int:
+    def _pixel_phase_shifts(self, phase_0_rgb):
+        rgb_phases = {}
+        for pixels, rgb in phase_0_rgb.items():
+            rgb_phases[pixels, 0] = rgb
+            for phase in range(1, 4):
+                msb = pixels & (1 << (self.PALETTE_DEPTH - 1))
+                pixels <<= 1 | (msb >> (self.PALETTE_DEPTH - 1))
+                rgb_phases[pixels, phase] = rgb
+        return rgb_phases
+
+    def bitmap_to_idx(self, pixels: np.array) -> int:
+        """Converts a bitmap of pixels into integer representation.
+
+        Args:
+            pixels: 1-D array of booleans, representing a window of pixels from
+              L to R.  Must be of size <= 8
+
+        Returns:
+            8-bit integer representation of pixels, suitable for use as an
+            index into palette arrays
+        """
         return np.packbits(
             # numpy uses big-endian representation which is the opposite
             # order to screen representation (i.e. LSB is the left-most
-            # screen pixel)
+            # screen pixel), so we need to flip the order
             np.flip(pixels, axis=0)
         )[0]
 

screen.py

@@ -59,13 +59,13 @@ class DHGRScreen:
         """
         image_rgb = np.empty((self.Y_RES, self.X_RES, 3), dtype=np.uint8)
         for y in range(self.Y_RES):
-            pixels = [False] * self.palette.PALETTE_DEPTH
+            bitmap_window = [False] * self.palette.PALETTE_DEPTH
             for x in range(self.X_RES):
                 # Maintain a sliding window of pixels of width PALETTE_DEPTH
-                pixels = pixels[1:] + [bitmap[y, x]]
+                bitmap_window = bitmap_window[1:] + [bitmap[y, x]]
                 image_rgb[y, x, :] = self.palette.RGB[
-                    self.palette.pixels_to_idx(
-                        np.array(pixels, dtype=bool)), x % 4]
+                    self.palette.bitmap_to_idx(
+                        np.array(bitmap_window, dtype=bool)), x % 4]
         return image_rgb
 
     @staticmethod