tools: rle_encode: Rework into proper functions

tools/rle_encode.py

@@ -1,6 +1,9 @@
+#!/usr/bin/env python3
+
+import sys
 from PIL import Image
 
-im = Image.open('pine64.png')
+def encode(im):
     pixels = im.load()
 
     rle = []
@@ -11,26 +14,33 @@ for y in range(im.height):
         for x in range(im.width):
             newpx = pixels[x, y]
             if newpx == px:
+                if rl < 255:
                     rl += 1
+                else:
+                    # Handle overflow
+                    rle.append(255)
+                    rle.append(0)
+                    rl = 1
                 continue
-        assert(rl < 255)
+
+            # Start a new run
             rle.append(rl)
             rl = 1
             px = newpx
+    # Handle the final run
     rle.append(rl)
 
-sx = 240
+    return (im.width, im.height, bytes(rle))
-sy = 240
-image = bytes(rle)
-
 
+def decode_to_ascii(image):
+    (sx, sy, rle) = image
     data = bytearray(2*sx)
     dp = 0
     black = ord('#')
     white = ord(' ')
     color = black
 
-for rl in image:
+    for rl in rle:
         while rl:
             data[dp] = color
             data[dp+1] = color
@@ -46,6 +56,12 @@ for rl in image:
         else:
             color = black
 
+    # Check the image is the correct length
     assert(dp == 0)
 
+image = encode(Image.open(sys.argv[1]))
+# This is kinda cool for testing but let's leave this disabled until we add
+# proper argument processing!
+#decode_to_ascii(image)
+print(f'# 1-bit RLE, generated from {sys.argv[1]}')
 print(image)