braille output

src/main.rs

@@ -1,6 +1,16 @@
-use std::{env, error::Error};
+use std::{
+    env,
+    error::Error,
+    io::{self, BufWriter, Write},
+};
 
-use image::{DynamicImage, ImageReader, Luma};
+use image::{ImageReader, Luma};
+
+const BRAILLE_FIRST_BYTE: u8 = 0xe2;
+const BRAILLE_SECOND_BYTE: u8 = 0xa0;
+const BRAILLE_HEIGHT: u8 = 4;
+const BRAILLE_BIT_MAPPING: [[u8; BRAILLE_HEIGHT as usize]; 2] =
+    [[0x1, 0x2, 0x4, 0x40], [0x8, 0x10, 0x20, 0x80]];
 
 #[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
 fn main() -> Result<(), Box<dyn Error>> {
@@ -12,16 +22,25 @@ fn main() -> Result<(), Box<dyn Error>> {
     ];
 
     let src = env::args().nth(1).ok_or("i need a source path")?;
-    let out_path = env::args().nth(2).ok_or("i need an output path")?;
     let mut img = ImageReader::open(&src)?.decode()?.to_luma32f();
-    let mut out = img.clone();
+
+    let mut out = BufWriter::new(io::stdout().lock());
+
+    let mut output_line = vec![0u8; img.width().div_ceil(2) as usize];
+    let mut lines_buffered: u8 = 0;
+
     for y in 0..img.height() {
         for x in 0..img.width() {
             let old_pixel = img.get_pixel(x, y);
             let old_luma = old_pixel.0[0];
-            let luma = if old_luma < 0.5 { 0. } else { 1. };
+            let white = old_luma > 0.5;
+            let luma = if white { 1. } else { 0. };
 
-            out.put_pixel(x, y, Luma([luma]));
+            // white pixels are filled because i'm targetting a dark mode site
+            if white {
+                output_line[(x / 2) as usize] |=
+                    BRAILLE_BIT_MAPPING[(x % 2) as usize][(y % 4) as usize];
+            }
 
             let error = old_luma - luma;
             for (dx, dy, quant) in kernel {
@@ -39,7 +58,29 @@ fn main() -> Result<(), Box<dyn Error>> {
                 img.put_pixel(x, y, Luma([corrected]));
             }
         }
+
+        lines_buffered += 1;
+        if lines_buffered == BRAILLE_HEIGHT {
+            for byte in &output_line {
+                if *byte == 0 {
+                    out.write_all(b" ").unwrap();
+                    continue;
+                }
+
+                let upper_2 = byte >> 6;
+                let lower_6 = byte & 0b111_111;
+                out.write_all(&[
+                    BRAILLE_FIRST_BYTE,
+                    BRAILLE_SECOND_BYTE | upper_2,
+                    0b10_000000 | lower_6,
+                ])
+                .unwrap();
+            }
+            out.write_all(b"\n").unwrap();
+
+            output_line.fill(0);
+            lines_buffered = 0;
+        }
     }
-    DynamicImage::from(out).into_luma8().save(out_path)?;
     Ok(())
 }