Basic POC cli working

src/dithering.rs

@@ -0,0 +1,46 @@
+use image::DynamicImage;
+
+pub fn atkinson_mono(img: &DynamicImage) -> Vec<u8> {
+    let mut gray = img.to_luma8();
+    let (w, h) = (gray.width() as usize, gray.height() as usize);
+    let pitch = (w + 7) >> 3;
+    let mut bits = vec![0u8; pitch * h];
+    let buf = gray.as_mut();
+
+    for y in 0..h {
+        let row = y * w;
+        for x in 0..w {
+            let i = row + x;
+            let old = buf[i];
+            let new = if old < 128 { 0 } else { 255 };
+            buf[i] = new;
+            let bit = new == 0;
+            if bit {
+                let byte = y * pitch + (x >> 3);
+                bits[byte] |= 128 >> (x & 7);
+            }
+            let err = ((old as i16) - (new as i16)) / 8;
+
+            if x + 1 < w {
+                buf[i + 1] = (buf[i + 1] as i16 + err).clamp(0, 255) as u8;
+            }
+            if x + 2 < w {
+                buf[i + 2] = (buf[i + 2] as i16 + err).clamp(0, 255) as u8;
+            }
+            if y + 1 < h {
+                let down = i + w;
+                if x > 0 {
+                    buf[down - 1] = (buf[down - 1] as i16 + err).clamp(0, 255) as u8;
+                }
+                buf[down] = (buf[down] as i16 + err).clamp(0, 255) as u8;
+                if x + 1 < w {
+                    buf[down + 1] = (buf[down + 1] as i16 + err).clamp(0, 255) as u8;
+                }
+                if y + 2 < h {
+                    buf[down + w] = (buf[down + w] as i16 + err).clamp(0, 255) as u8;
+                }
+            }
+        }
+    }
+    bits
+}