graphics: ssd1306: reimplement dithering using an ordered dither map

src/graphics/ssd1306.rs

@@ -1,12 +1,12 @@
 #![cfg(feature="oled")]
-use core::cmp::min;
+use core::{cmp::min, ops::{BitAnd, Shr}};
 
 use display_interface::DisplayError;
 use embedded_graphics::prelude::*;
 use esp_hal::{gpio::Output, i2c::master::I2c, Async};
 use figments::{liber8tion::{interpolate::Fract8, noise}, mappings::embedded_graphics::Matrix2DSpace, prelude::*};
 use embedded_graphics::pixelcolor::BinaryColor;
-use figments::pixels::PixelSink;
+use figments::pixels::AdditivePixelSink;
 use figments_render::output::OutputAsync;
 use ssd1306::{prelude::DisplayRotation, size::DisplaySize128x64, I2CDisplayInterface, Ssd1306Async};
 use embassy_time::Delay;
@@ -38,29 +38,38 @@ impl SsdPixel {
     }
 }
 
-impl PixelSink<BinaryColor> for SsdPixel {
-    fn set(&mut self, pixel: &BinaryColor) {
-        self.set_pixel(*pixel);
-    }
-}
+const DITHER_MAP: [u32;15] = [
+    0b1000_0000_0000_0000,
+    0b1000_0000_0010_0000,
+    0b1010_0000_0010_0000,
+    0b1010_0000_1010_0000,
+    0b1010_0100_1010_0000,
+    0b1010_0100_1010_0001,
+    0b1010_0101_1010_0001,
+    0b1010_0101_1010_0101,
+    0b1110_0101_1010_0101,
+    0b1110_0101_1011_0101,
+    0b1111_0101_1011_0101,
+    0b1111_0101_1111_0101,
+    0b1111_1101_1111_0101,
+    0b1111_1101_1111_0111,
+    0b1111_1111_1111_0111,
+];
 
-impl PixelBlend<BinaryColor> for SsdPixel {
-    fn blend_pixel(self, overlay: BinaryColor, opacity: Fract8) -> Self {
-        let scale = 48;
-        let x = self.coords.x * scale;
-        let y = self.coords.y * scale;
-        let stiple_idx = noise::inoise8(x as i16, y as i16);
-        if opacity >= stiple_idx {
-            self.set_pixel(overlay);
+impl AdditivePixelSink<BinaryColor> for SsdPixel {
+    fn add(&mut self, pixel: BinaryColor, opacity: Fract8) {
+        match opacity {
+            0 => (),
+            255 => self.set_pixel(pixel),
+            _ => {
+                let dither_value = DITHER_MAP[opacity as usize / 16];
+                let dither_x = self.coords.x % 4;
+                let dither_y = self.coords.x % 4;
+                if dither_value.shr(dither_x).shr(dither_y * 4).bitand(0x01) == 1 {
+                    self.set_pixel(pixel);
+                }
+            }
         }
-        self
-    }
-
-    fn multiply(self, overlay: BinaryColor) -> Self {
-        if overlay != self.get_pixel() {
-            self.set_pixel(overlay);
-        }
-        self
     }
 }
 
@@ -195,9 +204,9 @@ impl DrawTarget for SsdOutput {
 
     fn clear(&mut self, color: Self::Color) -> Result<(), Self::Error> {
         if color.is_on() {
-            self.pixbuf.fill(255);
+            self.pixbuf.fill_with(|| { 255 });
         } else {
-            self.pixbuf.fill(0);
+            self.pixbuf.fill_with(|| { 0 });
         }
         Ok(())
     }