Add 256 color support.

Add API function pew.palette([pal], [offset=0]) that takes a sequence of R, G, B, R, G, B... byte values for up to 256 colors (blue component is ignored here) and an optional offset to cyclically shift the palette. Passing no palette preserves the previous one and only adjusts the offset, which may be useful for some animations. Passing an empty palette or None sets a default palette (described at https://hackaday.io/project/167369-picopew/log/171107-256-colors). Changes take effect at the next pew.show().

The palette is preserved by pew.init(), much like pew.brightness(), so that a choice made by the user before starting a program stays in effect, unless the program explicitly sets its own palette. Program tint.py is provided to allow selection of some offsets in the default palette that match the color schemes of other PewPew devices.

Generating the default palette in code is a lot more compact that including it as a bytes literal. Zlib compression and Base64 encoding would be a little better still but I did not examine their memory and time requirements.

pew.py

@@ -36,6 +36,28 @@ def brightness(level):
     _i2c.writeto_mem(80, 0xfd, b'\x01')
 
 
+def palette(pal=False, offset=0):
+    global _palette, _palettesize, _paletteoffset
+    if pal is not False:
+        if not pal:
+            pal = bytearray(768)
+            for i in range(256):
+                if (i & 0xc0) == 0:
+                    b = (255, 121, 42, 7)[(i >> 4) & 3]
+                    pal[3*i] = (b*(0, 0, 255, 160)[i & 3] + 127)//255
+                    pal[3*i+1] = b*(i & 1)
+                elif (i & 0xc0) == 0x40:
+                    b = (0, 15, 89, 255)[i & 3]
+                    pal[3*i] = (b*(0, 64, 255, 255)[(i >> 4) & 3] + 127)//255
+                    pal[3*i+1] = (b*(255, 255, 255, 0)[(i >> 4) & 3] + 127)//255
+                else:
+                    pal[3*i] = (0, 1, 2, 4, 8, 15, 24, 35, 50, 68, 89, 114, 143, 176, 213, 255)[(i >> 3) & 15]
+                    pal[3*i+1] = (0, 2, 10, 28, 60, 106, 171, 255)[i & 7]
+        _palette = pal
+    _palettesize = len(_palette)//3
+    _paletteoffset = offset % _palettesize
+
+
 def show(pix):
     global _buffer, _i2c
 
@@ -45,11 +67,11 @@ def show(pix):
     for y in range(8):
         position = y*width
         for x in range(8):
-            pixel = buffer[position]
+            pixel = 3*((buffer[position] + _paletteoffset) % _palettesize)
             position += 1
-            _buffer[index] = 0xff if pixel & 1 else 0
+            _buffer[index] = _palette[pixel + 1]
             index += 1
-            _buffer[index] = 0xa0 if pixel & 2 else 0
+            _buffer[index] = _palette[pixel]
             index += 1
     _i2c.writeto_mem(80, 0x00, _buffer)
 
@@ -246,4 +268,5 @@ def handler(p):
     _i2c.writeto_mem(80, 0xfd, b'\x00') # go to LED control page
     _i2c.writeto_mem(80, 0x00, b'\xff'*16) # all 128 LEDs on
 
+    palette(None)
     brightness(7)

programs/tint.py

@@ -0,0 +1,44 @@
+import pew
+
+pew.init()
+choice = {64: 1, 80: 2, 96: 3, 112: 4}.get(pew._paletteoffset, 0)
+pew.palette(None)
+screen = pew.Pix()
+
+keyhistory = 0
+def keyevents():
+	global keyhistory
+	keys = pew.keys()
+	events = keys & (~keyhistory | (keyhistory & (keyhistory >> 8) & (keyhistory >> 16) & (keyhistory >> 24)))
+	keyhistory = ((keyhistory & 0x3FFFFF) << 8) | keys
+	return events
+
+def paint():
+	if choice == 0:
+		for i in range(3):
+			screen.box(i+1, 2*i+1, 1, 2, 2)
+	else:
+		for i in range(3):
+			screen.box(32+i+1, 2*i+1, 1, 2, 1)
+	for c in range(1, 5):
+		if choice == c:
+			for i in range(3):
+				screen.box(48+c*16+i+1, 2*i+1, 1+c, 2, 2)
+		else:
+			screen.box(48+c*16+1, 1, 1 + c + (0 if choice > c else 1), 6, 1)
+	pew.show(screen)
+
+paint()
+while pew.keys():
+	pew.tick(0.1)
+while True:
+	k = keyevents()
+	if k & pew.K_UP:
+		choice = (choice - 1) % 5
+	if k & pew.K_DOWN:
+		choice = (choice + 1) % 5
+	if k & pew.K_O:
+		pew.palette(offset = (0, 64, 80, 96, 112)[choice])
+		break
+	paint()
+	pew.tick(0.06)