From 322a951d51ce8b13ab5ec1b3cab35bbf92922e75 Mon Sep 17 00:00:00 2001
From: Jurn Wubben <jsw@jsw.tf>
Date: Thu, 25 Sep 2025 21:26:07 +0200
Subject: [PATCH] Changing the dithering algorithm

---
 src/dithering.rs | 56 ++++++++++++++++++++----------------------------
 1 file changed, 23 insertions(+), 33 deletions(-)

diff --git a/src/dithering.rs b/src/dithering.rs
index 8006276..cb25727 100644
--- a/src/dithering.rs
+++ b/src/dithering.rs
@@ -1,45 +1,35 @@
-use image::DynamicImage;
+use image::{DynamicImage, imageops};
 
 pub fn atkinson_mono(img: &DynamicImage) -> Vec<u8> {
     let mut gray = img.to_luma8();
+    imageops::dither(&mut gray, &imageops::colorops::BiLevel);
+
     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();
+    let stride = (w + 7) >> 3;
+    let mut bits = vec![0u8; stride * h];
+    let pix = gray.as_raw();
 
     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;
+        let row_off = y * w;
+        let bit_off = y * stride;
+        let chunks = w >> 3;
+        let tail = w & 7;
 
-            if x + 1 < w {
-                buf[i + 1] = (buf[i + 1] as i16 + err).clamp(0, 255) as u8;
+        for x8 in 0..chunks {
+            let p = &pix[row_off + (x8 << 3)..][..8];
+            let mut byte = 0u8;
+            for (bit, &v) in p.iter().enumerate() {
+                byte |= ((v < 128) as u8) << (7 - bit);
             }
-            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[bit_off + x8] = byte;
+        }
+
+        if tail != 0 {
+            let mut last = 0u8;
+            for (bit, &v) in pix[row_off + (chunks << 3)..][..tail].iter().enumerate() {
+                last |= ((v < 128) as u8) << (7 - bit);
             }
+            bits[bit_off + chunks] = last;
         }
     }
     bits