draw565: Switch to a different palette for RLE 2-bit images

This is an incompatible change... older 2-bit images will need to be
re-encoded to display correctly.

5 files changed, 182 insertions, 66 deletions

diff --git a/res/app_icon.png b/res/app_icon.png
index 574f75f..438cded 100644
--- a/res/app_icon.png
+++ b/res/app_icon.png
diff --git a/tools/rle_encode.py b/tools/rle_encode.py
index 36ada32..6dccbd7 100755
--- a/tools/rle_encode.py
+++ b/tools/rle_encode.py
@@ -8,6 +8,109 @@ import sys
 import os.path
 from PIL import Image
 
+def clut8_rgb888(i):
+    """Reference CLUT for wasp-os.
+
+    Technically speaking this is not a CLUT because the we lookup the colours
+    algorithmically to avoid the cost of a genuine CLUT. The palette is
+    designed to be fairly easy to generate algorithmically.
+
+    The palette includes all 216 web-safe colours together 4 grays and
+    36 additional colours that target "gaps" at the brighter end of the web
+    safe set. There are 11 greys (plus black and white) although two are
+    fairly close together.
+
+    :param int i: Index (from 0..255 inclusive) into the CLUT
+    :return:      24-bit colour in RGB888 format
+    """
+    if i < 216:
+        rgb888  = ( i  % 6) * 0x33
+        rg = i // 6
+        rgb888 += (rg  % 6) * 0x3300
+        rgb888 += (rg // 6) * 0x330000
+    elif i < 252:
+        i -= 216
+        rgb888  =     0x7f + (( i  % 3) * 0x33)
+        rg = i // 3
+        rgb888 +=   0x4c00 + ((rg  % 4) * 0x3300)
+        rgb888 += 0x7f0000 + ((rg // 4) * 0x330000)
+    else:
+        i -= 252
+        rgb888 = 0x2c2c2c + (0x101010 * i)
+
+    return rgb888
+
+def clut8_rgb565(i):
+    """RBG565 CLUT for wasp-os.
+
+    This CLUT implements the same palette as :py:meth:`clut8_888` but
+    outputs RGB565 pixels.
+
+    .. note::
+
+        This function is unused within this file but needs to be
+        maintained alongside the reference clut so it is reproduced
+        here.
+
+    :param int i: Index (from 0..255 inclusive) into the CLUT
+    :return:      16-bit colour in RGB565 format
+    """
+    if i < 216:
+        rgb565  = (( i  % 6) * 0x33) >> 3
+        rg = i // 6
+        rgb565 += ((rg  % 6) * (0x33 << 3)) & 0x07e0
+        rgb565 += ((rg // 6) * (0x33 << 8)) & 0xf800
+    elif i < 252:
+        i -= 216
+        rgb565  = (0x7f + (( i  % 3) * 0x33)) >> 3
+        rg = i // 3
+        rgb565 += ((0x4c << 3) + ((rg  % 4) * (0x33 << 3))) & 0x07e0
+        rgb565 += ((0x7f << 8) + ((rg // 4) * (0x33 << 8))) & 0xf800
+    else:
+        i -= 252
+        gr6 = (0x2c + (0x10 * i)) >> 2
+        gr5 = gr6 >> 1
+        rgb565 = (gr5 << 11) + (gr6 << 5) + gr5
+
+    return rgb565
+
+class ReverseCLUT:
+    def __init__(self, clut):
+        l = []
+        for i in range(256):
+            l.append(clut(i))
+        self.clut = tuple(l)
+        self.lookup = {}
+
+    def __call__(self, rgb888):
+        """Compare rgb888 to every element of the CLUT and pick the
+        closest match.
+        """
+        if rgb888 in self.lookup:
+            return self.lookup[rgb888]
+
+        best = 200000
+        index = -1
+        clut = self.clut
+        r = rgb888 >> 16
+        g = (rgb888 >> 8) & 0xff
+        b = rgb888 & 0xff
+
+        for i in range(256):
+            candidate = clut[i]
+            rd = r - (candidate >> 16)
+            gd = g - ((candidate >> 8) & 0xff)
+            bd = b - (candidate & 0xff)
+            # This is the Euclidian distance (squared)
+            distance = rd * rd + gd * gd + bd * bd
+            if distance < best:
+                best = distance
+                index = i
+
+        self.lookup[rgb888] = index
+        #print(f'# #{rgb888:06x} -> #{clut8_rgb888(index):06x}')
+        return index
+
 def varname(p):
     return os.path.basename(os.path.splitext(p)[0])
 
@@ -62,15 +165,18 @@ def encode_2bit(im):
     assert(im.width <= 255)
     assert(im.height <= 255)
 
+    full_palette = ReverseCLUT(clut8_rgb888)
+
     rle = []
     rl = 0
     px = pixels[0, 0]
-    palette = [0, 0xfc, 0x2d, 0xff]
+    # black, grey25, grey50, white
+    palette = [0, 254, 219, 215]
     next_color = 1
 
     def encode_pixel(px, rl):
         nonlocal next_color
-        px = (px[0] & 0xe0) | ((px[1] & 0xe0) >> 3) | ((px[2] & 0xc0) >> 6)
+        px = full_palette((px[0] << 16) + (px[1] << 8) + px[2])
         if px not in palette:
             rle.append(next_color << 6)
             rle.append(px)
diff --git a/wasp/apps/gameoflife.py b/wasp/apps/gameoflife.py
index 080c214..80c5528 100644
--- a/wasp/apps/gameoflife.py
+++ b/wasp/apps/gameoflife.py
@@ -118,11 +118,11 @@ def game_of_life(b, xmax: int, ymax: int, nb):
 icon = (
     b'\x02'
     b'`@'
-    b'?\xff\xff\xee@\xd7B\x02B\x02B?\x16L?\x15'
+    b'?\xff\xff\xee@\xf8B\x02B\x02B?\x16L?\x15'
     b'L?\x16B\x02B\x02B?\x1bB?\x1eD?\x1d'
-    b'D?\x1eB?\x17\x80\xbe\x82\x02\x82\x06\x82\x02\x82?'
+    b'D?\x1eB?\x17\x80\xee\x82\x02\x82\x06\x82\x02\x82?'
     b'\x0e\x88\x04\x88?\r\x88\x04\x88?\x0e\x82\x02\x82\x06B'
-    b'\x02\x82?\x03\xc0\x97\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02'
+    b'\x02\x82?\x03\xc0\x89\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02'
     b'\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc25\xec4\xec5'
     b'\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02\xc2\x02'
     b'\xc2\x02\xc2\x02\xc2*B\x02B\x12\xc2\x06B\x06\xc2\x12'
diff --git a/wasp/draw565.py b/wasp/draw565.py
index e7914b8..21b23ed 100644
--- a/wasp/draw565.py
+++ b/wasp/draw565.py
@@ -35,15 +35,25 @@ def _bitblit(bitbuf, pixels, bgfg: int, count: int):
             pxp += 1
 
 @micropython.viper
-def _expand_rgb(eightbit: int) -> int:
-    r = eightbit >> 5
-    r = (r << 2) | (r >> 1)
-    g = (eightbit >> 2) & 7
-    g *= 9
-    b = eightbit & 3
-    b *= 10
-
-    return (r << 11) | (g << 5) | b
+def _clut8_rgb565(i: int) -> int:
+    if i < 216:
+        rgb565  = (( i  % 6) * 0x33) >> 3
+        rg = i // 6
+        rgb565 += ((rg  % 6) * (0x33 << 3)) & 0x07e0
+        rgb565 += ((rg // 6) * (0x33 << 8)) & 0xf800
+    elif i < 252:
+        i -= 216
+        rgb565  = (0x7f + (( i  % 3) * 0x33)) >> 3
+        rg = i // 3
+        rgb565 += ((0x4c << 3) + ((rg  % 4) * (0x33 << 3))) & 0x07e0
+        rgb565 += ((0x7f << 8) + ((rg // 4) * (0x33 << 8))) & 0xf800
+    else:
+        i -= 252
+        gr6 = (0x2c + (0x10 * i)) >> 2
+        gr5 = gr6 >> 1
+        rgb565 = (gr5 << 11) + (gr6 << 5) + gr5
+
+    return rgb565
 
 @micropython.viper
 def _fill(mv, color: int, count: int, offset: int):
@@ -183,7 +193,7 @@ class Draw565(object):
             sx *= 2
             sy //= 2
 
-        palette = array.array('H', (0, 0xfffe, 0x7bef, 0xffff))
+        palette = array.array('H', (0, 0x4a69, 0x7bef, 0xffff))
         next_color = 1
         rl = 0
         buf = memoryview(display.linebuffer)[0:2*sx]
@@ -204,7 +214,7 @@ class Draw565(object):
                 if op >= 255:
                     continue
             else:
-                palette[next_color] = _expand_rgb(op)
+                palette[next_color] = _clut8_rgb565(op)
                 if next_color < 3:
                     next_color += 1
                 else:
diff --git a/wasp/icons.py b/wasp/icons.py
index 9bfa92a..dec982a 100644
--- a/wasp/icons.py
+++ b/wasp/icons.py
@@ -21,10 +21,10 @@ bomb = (
 app = (
     b'\x02'
     b'`@'
-    b'\x1e@md<d<d;f?X\xec2\xf0/'
+    b'\x1e@\x81d<d<d;f?X\xec2\xf0/'
     b'\xf2-\xf4,\xc3.\xc3,\xc3.\xc3,\xc3.\xc3,'
-    b'\xc3.\xc3,\xc3.\xc3,\xc3\x0c\x80\xfc\x83\x10\xc0]'
-    b'\xc3\x0c@\xffC,C\n\x87\x0c\xc7\nC,C\t'
+    b'\xc3.\xc3,\xc3.\xc3,\xc3\x0c\x80\xd2\x83\x10\xc0C'
+    b'\xc3\x0c@\xd7C,C\n\x87\x0c\xc7\nC,C\t'
     b'\x83\x02\x84\n\xc4\x02\xc3\tC,C\x08\x82\x07\x82\x08'
     b'\xc2\x07\xc2\x08C,C\x07\x82\t\x82\x06\xc2\t\xc2\x07'
     b'C,C\x06\x82\x0b\x82\x04\xc2\x0b\xc2\x06C,C\x06'
@@ -36,7 +36,7 @@ app = (
     b'C+D\x08\x82\t\x82\x04\xc2\t\xc2\x08C*E\t'
     b'\x8c\x04\xcc\tC*E\n\x8b\x04\xcb\nC*E.'
     b'C*E.C*E.C*E.C*E\n'
-    b'\x80\xe9\x8b\x04\xc0o\xcb\nC+D\t\x8c\x04\xcc\t'
+    b'\x80\xbb\x8b\x04\xc0X\xcb\nC+D\t\x8c\x04\xcc\t'
     b'C,C\x08\x82\t\x82\x04\xc2\t\xc2\x08C,C\x07'
     b'\x82\n\x82\x04\xc2\n\xc2\x07C,C\x06\x82\x0b\x82\x04'
     b'\xc2\x0b\xc1\x07C,C\x06\x82\x0b\x82\x04\xc2\x0b\xc2\x06'
@@ -49,14 +49,14 @@ app = (
     b'C,C\n\x86\x0e\xc6\nC,C\x0c\x83\x10\xc3\x0c'
     b'C,C.C,C.C,C.C,C.'
     b'C,C.C,t-r/p2l?X@'
-    b'mf;d<d<d\x1e'
+    b'\x81f;d<d<d\x1e'
 )
 
 # 2-bit RLE, generated from res/clock_icon.png, 288 bytes
 clock = (
     b'\x02'
     b'`@'
-    b'?\xff\xff\xff\xff\xff\xff\x8e@\xb6F\r\xc6!E\x0b'
+    b'?\xff\xff\xff\xff\xff\xff\x8e@\xacF\r\xc6!E\x0b'
     b'\xc8\x0cH\x0b\xca\x1dI\x07\xcc\nH\n\xcc\x1bK\x06'
     b'\xce\x08C\x02C\n\xc4\x05\xc4\x1aD\x03D\x06\xc2\x08'
     b'\xc4\rC\t\xc4\x07\xc3\x19D\x05D\x10\xc4\x0cC\t'
@@ -76,62 +76,62 @@ clock = (
     b'E\t\xcf?\xff\xff\xff\xff\xff\xff\xff\xffk'
 )
 
-# 2-bit RLE, generated from res/settings_icon.png, 472 bytes
+# 2-bit RLE, generated from res/settings_icon.png, 468 bytes
 settings = (
     b'\x02'
     b'`@'
-    b'\x1e@md<d<d;f?X\xec2\xf0/'
-    b'\xf2-\xf4,\xc3.\xc3,\xc3.\xc3,\xc3.\xc3,'
-    b'\xc3\x14\x80\xb7\x86\x14\xc3,\xc3\x13\x88\x13\xc3,\xc3\x13'
-    b'\x88\x13\xc3,\xc3\x12\x83\x04\x83\x12\xc3,\xc3\n\x84\x04'
-    b'\x83\x04\x83\x04\x84\n\xc3,\xc3\t\x86\x01\x85\x04\x85\x01'
-    b'\x86\t\xc3,\xc3\x08\x8c\x05\x8d\x08\xc3,\xc3\x07\x84\x02'
-    b'\x86\x08\x86\x02\x84\x07\xc3,\xc3\x07\x83\x05\x81\x0e\x81\x05'
-    b'\x83\x07\xc3,\xc3\x07\x83\x1a\x83\x07\xc3,\xc3\x07\x84\x18'
-    b'\x84\x07\xc3,\xc3\x08\x83\n\xc0o\xc4\n\x83\x08@\xff'
-    b'C,C\t\x83\x06\xca\x06\x83\tC,C\x08\x83\x06'
-    b'\xcc\x06\x83\x08C,C\x08\x83\x05\xc4\x06\xc4\x05\x83\x08'
-    b'C+D\x06\x85\x04\xc4\x08\xc4\x04\x85\x06C*E\x04'
-    b'\x86\x05\xc3\n\xc3\x05\x86\x04C*E\x03\x87\x05\xc2\x0c'
-    b'\xc2\x05\x87\x03C*E\x03\x83\x08\xc3\x0c\xc3\x08\x83\x03'
-    b'C*E\x03\x83\x08\xc3\x0c\xc3\x08\x83\x03C*E\x03'
-    b'\x83\x08\xc3\x0c\xc3\x08\x83\x03C*E\x03\x83\x08\xc3\x0c'
-    b'\xc3\x08\x83\x03C*E\x03\x86\x06\xc2\x0c\xc2\x05\x87\x03'
-    b'C+D\x04\x86\x05\xc3\n\xc3\x05\x86\x04C,C\x05'
-    b'\x86\x04\xc4\x08\xc4\x04\x85\x06C,C\x08\x83\x05\xc4\x06'
-    b'\xc4\x05\x83\x08C,C\x08\x83\x06\xcc\x06\x83\x08C,'
-    b'C\t\x83\x06\xca\x06\x83\tC,C\x08\x83\n\xc4\n'
-    b'\x83\x08C,C\x07\x84\x18\x84\x07C,C\x07\x83\x1a'
-    b'\x83\x07C,C\x07\x83\x05\x81\x0e\x81\x05\x83\x07C,'
-    b'C\x07\x84\x03\x85\x08\x86\x02\x84\x07C,C\x08\x8d\x04'
-    b'\x8d\x08C,C\t\x86\x01\x85\x04\x85\x01\x86\tC,'
-    b'C\n\x84\x04\x83\x04\x83\x04\x84\nC,C\x12\x83\x04'
-    b'\x83\x12C,C\x13\x88\x13C,C\x13\x88\x13C,'
-    b'C\x14\x86\x14C,C.C,C.C,C.'
-    b'C,t-r/p2l?X\x80m\xa6;\xa4'
-    b'<\xa4<\xa4\x1e'
+    b'\x1e\xa4<\xa4<\xa4;\xa6?X\xec2\xf0/\xf2-'
+    b'\xf4,\xc3.\xc3,\xc3.\xc3,\xc3.\xc3,\xc3\x14'
+    b'@\xadF\x14\xc3,\xc3\x13H\x13\xc3,\xc3\x13H\x13'
+    b'\xc3,\xc3\x12C\x04C\x12\xc3,\xc3\nD\x04C\x04'
+    b'C\x04D\n\xc3,\xc3\tF\x01E\x04E\x01F\t'
+    b'\xc3,\xc3\x08L\x05M\x08\xc3,\xc3\x07D\x02F\x08'
+    b'F\x02D\x07\xc3,\xc3\x07C\x05A\x0eA\x05C\x07'
+    b'\xc3,\xc3\x07C\x1aC\x07\xc3,\xc3\x07D\x18D\x07'
+    b'\xc3,\xc3\x08C\n\x80\xdd\x84\nC\x08\xc3,\xc3\t'
+    b'C\x06\x8a\x06C\t\xc3,\xc3\x08C\x06\x8c\x06C\x08'
+    b'\xc3,\xc3\x08C\x05\x84\x06\x84\x05C\x08\xc3+\xc4\x06'
+    b'E\x04\x84\x08\x84\x04E\x06\xc3*\xc5\x04F\x05\x83\n'
+    b'\x83\x05F\x04\xc3*\xc5\x03G\x05\x82\x0c\x82\x05G\x03'
+    b'\xc3*\xc5\x03C\x08\x83\x0c\x83\x08C\x03\xc3*\xc5\x03'
+    b'C\x08\x83\x0c\x83\x08C\x03\xc3*\xc5\x03C\x08\x83\x0c'
+    b'\x83\x08C\x03\xc3*\xc5\x03C\x08\x83\x0c\x83\x08C\x03'
+    b'\xc3*\xc5\x03F\x06\x82\x0c\x82\x05G\x03\xc3+\xc4\x04'
+    b'F\x05\x83\n\x83\x05F\x04\xc3,\xc3\x05F\x04\x84\x08'
+    b'\x84\x04E\x06\xc3,\xc3\x08C\x05\x84\x06\x84\x05C\x08'
+    b'\xc3,\xc3\x08C\x06\x8c\x06C\x08\xc3,\xc3\tC\x06'
+    b'\x8a\x06C\t\xc3,\xc3\x08C\n\x84\nC\x08\xc3,'
+    b'\xc3\x07D\x18D\x07\xc3,\xc3\x07C\x1aC\x07\xc3,'
+    b'\xc3\x07C\x05A\x0eA\x05C\x07\xc3,\xc3\x07D\x03'
+    b'E\x08F\x02D\x07\xc3,\xc3\x08M\x04M\x08\xc3,'
+    b'\xc3\tF\x01E\x04E\x01F\t\xc3,\xc3\nD\x04'
+    b'C\x04C\x04D\n\xc3,\xc3\x12C\x04C\x12\xc3,'
+    b'\xc3\x13H\x13\xc3,\xc3\x13H\x13\xc3,\xc3\x14F\x14'
+    b'\xc3,\xc3.\xc3,\xc3.\xc3,\xc3.\xc3,\xf4-'
+    b'\xf2/\xf02\xec?X\xc0\xdb\xe6;\xe4<\xe4<\xe4'
+    b'\x1e'
 )
 
-# 2-bit RLE, generated from res/torch_icon.png, 247 bytes
+# 2-bit RLE, generated from res/torch_icon.png, 245 bytes
 torch = (
     b'\x02'
     b'`@'
-    b'?\xff\xff\xff\xff\xff\xff\xff&\xc6\x0c@\xfdB?\n'
+    b'?\xff\xff\xff\xff\xff\xff\xff&\xc6\x0c@\xd4B?\n'
     b'\xca\tD?\x08\xc4\x06\xc2\x07F?\x07\xc3\x07\xc2\x06'
     b'H?\x06\xc2\n\xc1\x04G\xc2A8\xc5\x08\xc2\t\xc2'
     b'\x02F\xc3C7\xc7\x06\xc2\x0b\xc1F\xc2F\x1e\xe8\n'
     b'\xc2C\xc3H\x1d\xe8\x0c\xc1N\x1d\xc2%\xc1\x0b\xc2N'
-    b'\x1d\xc2%\xc1\x0c\xc1N\x1d\xc2\x04\x80m\x9d\x04\xc1\x0b'
-    b'\xc2N\x1d\xc2\x06\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81'
-    b'\x03\x81\x06\xc1\x0c\xc1N\x1d\xc2\x04\x9d\x04\xc1\x0b\xc2C'
-    b'\xcaA\x1d\xc2\x06\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81'
-    b'\x03\x81\x06\xc1\x0c\xc1N\x1d\xc2\x04\x9d\x04\xc1\x0b\xc2N'
-    b'\x1d\xc2%\xc1\x0c\xc1N\x1d\xc2%\xc1\x0b\xc2N\x1d\xe8'
-    b'\x0c\xc1N\x1e\xe8\n\xc2C\xc3H?\x05\xc2\x0b\xc1F'
-    b'\xc2F?\x06\xc2\t\xc2\x02F\xc3C?\x06\xc2\n\xc1'
-    b'\x04G\xc2A?\x07\xc3\x07\xc2\x06H?\x08\xc4\x06\xc2'
-    b'\x07F?\n\xca\tD?\r\xc6\x0cB?\xff\xff\xff'
-    b'\xff\xff\xff\x95'
+    b'\x1d\xc2%\xc1\x0c\xc1N\x1d\xc2\x04\x9d\x04\xc1\x0b\xc2N'
+    b'\x1d\xc2\x06\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81'
+    b'\x06\xc1\x0c\xc1N\x1d\xc2\x04\x9d\x04\xc1\x0b\xc2C\xcaA'
+    b'\x1d\xc2\x06\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81\x03\x81'
+    b'\x06\xc1\x0c\xc1N\x1d\xc2\x04\x9d\x04\xc1\x0b\xc2N\x1d\xc2'
+    b'%\xc1\x0c\xc1N\x1d\xc2%\xc1\x0b\xc2N\x1d\xe8\x0c\xc1'
+    b'N\x1e\xe8\n\xc2C\xc3H?\x05\xc2\x0b\xc1F\xc2F'
+    b'?\x06\xc2\t\xc2\x02F\xc3C?\x06\xc2\n\xc1\x04G'
+    b'\xc2A?\x07\xc3\x07\xc2\x06H?\x08\xc4\x06\xc2\x07F'
+    b'?\n\xca\tD?\r\xc6\x0cB?\xff\xff\xff\xff\xff'
+    b'\xff\x95'
 )
 
 # 1-bit RLE, generated from res/up_arrow.png, 16 bytes