Add a screen-to-backlight module.

This is a heavily optimised (~20ms -> ~4.4ms frame) version of PrestoLight.

Co-authored-by: Phil Howard <[email protected]>

modules/py_frozen/backlight.py

@@ -0,0 +1,75 @@
+import plasma
+import micropython
+
+
+class Zone(object):
+    SIZE = 80
+
+    # A section of the screen we'll use for sampling.
+    # We're using 80 x 80 sections and sampling 49 points within that space
+    def __init__(self, x, y, width=240):
+        self.colours = []
+
+        # Pre calculate the ranges to use later
+        # Calculates the coordinates in terms of RGB56 / two bytes per pixel
+        self.x_range = range(x * 2, (x + self.SIZE) * 2, 10 * 2)
+        self.y_range = range(y * 2, (y + self.SIZE) * 2, 10 * 2)
+
+        # Calculate the offsets for every pixel we need to sample
+        # A tuple is slightly less expensive than a list to iterate
+        self.pixels = tuple([y * width + x for y in self.y_range for x in self.x_range])
+        self.samples = len(self.pixels)
+
+    @micropython.native
+    def return_avg(self, mv):
+        # Running total of the RGB values for our average calculation later
+        r_value, g_value, b_value = 0, 0, 0
+
+        for offset in self.pixels:
+            # Grab the pixel colour value back from the framebuffer
+            # This will be in RGB565 - RRRRRGGGGGGBBBBB
+            rgb = (mv[offset] << 8) | mv[offset + 1]
+
+            # Now we need to sort and arrange those bits into their R G and B values
+            # We can't get back the exact value due to the destructive nature of converting to RGB565
+            # But it's close enough for displaying a colour on the backlight :)
+            # We're shifting the 5, 6 and 5 bits into the most significant places
+            r_value += (rgb >> 8) & 0b11111000
+            g_value += (rgb >> 3) & 0b11111100
+            b_value += (rgb << 3) & 0b11111000
+
+        # Now we finish the average calculation and return the value as an integer
+        return (
+            int(r_value / self.samples),
+            int(g_value / self.samples),
+            int(b_value / self.samples)
+        )
+
+
+class Reactive(object):
+    def __init__(self, surface, width=240, height=240):
+        self.mv = surface if isinstance(surface, memoryview) else memoryview(surface)
+
+        MAX = width - Zone.SIZE
+        MID = width // 2 - Zone.SIZE // 2
+        MIN = 0
+        W = width
+
+        # The index for each section matches the index for the Backlight LED
+        # Zone 0 is in the bottom right corner LED as you're looking at the screen
+        # And the LEDs proceed around counter-clockwise
+        # A tuple is slightly less expensive than a list to iterate
+        self.zones = (Zone(MAX, MAX, W), Zone(MAX, MID, W), Zone(MAX, MIN, W), Zone(MID, MIN, W),
+                      Zone(MIN, MIN, W), Zone(MIN, MID, W), Zone(MIN, MAX, W))
+
+        self.bl = plasma.WS2812(7, 0, 0, 33)
+        self.bl.start()
+
+    @micropython.native
+    def update(self):
+        mv = self.mv
+        i = 0
+        # For each section we get the average colour in that area and set the backlight LED to that colour
+        for zone in self.zones:
+            self.bl.set_rgb(i, *zone.return_avg(mv))
+            i += 1