Changed out dithering algorithm and added auto brighting

src/dithering.rs

@@ -1,35 +1,32 @@
-use image::{DynamicImage, imageops};
+use image::{
+    DynamicImage, GrayImage,
+    imageops::{self, colorops},
+};
+pub fn auto_brighten(gray: &mut GrayImage) -> () {
+    let avg = gray.pixels().map(|p| p.0[0] as u32).sum::<u32>() / gray.len() as u32;
 
-pub fn atkinson_mono(img: &DynamicImage) -> Vec<u8> {
-    let mut gray = img.to_luma8();
-    imageops::dither(&mut gray, &imageops::colorops::BiLevel);
+    if avg < 100 {
+        colorops::brighten_in_place(gray, 40);
+        colorops::contrast_in_place(gray, 25.0);
+    } else if avg > 180 {
+        colorops::brighten_in_place(gray, -15);
+    }
+}
+
+pub fn dither(gray: &mut GrayImage) -> Vec<u8> {
+    imageops::dither(gray, &imageops::colorops::BiLevel);
 
     let (w, h) = (gray.width() as usize, gray.height() as usize);
-    let stride = (w + 7) >> 3;
-    let mut bits = vec![0u8; stride * h];
-    let pix = gray.as_raw();
+    let pitch = (w + 7) >> 3;
+    let mut bits = vec![0u8; pitch * h];
 
     for y in 0..h {
-        let row_off = y * w;
-        let bit_off = y * stride;
-        let chunks = w >> 3;
-        let tail = w & 7;
-
-        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);
+        for x in 0..w {
+            let byte = y * pitch + (x >> 3);
+            let bit = 7 - (x & 7);
+            if gray[(x as u32, y as u32)].0[0] == 0 {
+                bits[byte] |= 1 << bit;
             }
-            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

src/escpos.rs

@@ -1,5 +1,8 @@
-use crate::dithering::atkinson_mono;
-use image::{DynamicImage, imageops::FilterType};
+use crate::dithering::{auto_brighten, dither};
+use image::{
+    DynamicImage,
+    imageops::{FilterType, colorops},
+};
 
 const MAX_WIDTH: u32 = 384;
 
@@ -26,7 +29,10 @@ pub fn escpos_raster(
     let img = if swap { &img.rotate90() } else { &img };
     let img = img.resize(w, h, FilterType::Triangle);
 
-    let mono = atkinson_mono(&img);
+    let mut gray = img.to_luma8();
+    auto_brighten(&mut gray);
+
+    let mono = dither(&mut gray);
     let (width_px, height_px) = (img.width() as u16, img.height() as u16);
     let width_bytes = ((width_px + 7) >> 3) as u16;