onefetch_image/
sixel.rs

1use crate::get_dimensions;
2use anyhow::{Context, Result};
3use color_quant::NeuQuant;
4use image::{
5    imageops::{colorops, FilterType},
6    DynamicImage, GenericImageView, ImageBuffer, Pixel, Rgb,
7};
8use libc::{
9    c_void, poll, pollfd, read, tcgetattr, tcsetattr, termios, ECHO, ICANON, POLLIN, STDIN_FILENO,
10    TCSANOW,
11};
12use std::io::{stdout, Write};
13use std::time::Instant;
14
15pub struct SixelBackend {}
16
17impl SixelBackend {
18    pub fn new() -> Self {
19        Self {}
20    }
21
22    pub fn supported() -> bool {
23        // save terminal attributes and disable canonical input processing mode
24        let old_attributes = unsafe {
25            let mut old_attributes: termios = std::mem::zeroed();
26            tcgetattr(STDIN_FILENO, &mut old_attributes);
27
28            let mut new_attributes = old_attributes;
29            new_attributes.c_lflag &= !ICANON;
30            new_attributes.c_lflag &= !ECHO;
31            tcsetattr(STDIN_FILENO, TCSANOW, &new_attributes);
32            old_attributes
33        };
34
35        // ask for the primary device attribute string
36        print!("\x1B[c");
37        stdout().flush().unwrap();
38
39        let start_time = Instant::now();
40        let mut stdin_pollfd = pollfd {
41            fd: STDIN_FILENO,
42            events: POLLIN,
43            revents: 0,
44        };
45        let mut buf = Vec::<u8>::new();
46        loop {
47            // check for timeout while polling to avoid blocking the main thread
48            while unsafe { poll(&mut stdin_pollfd, 1, 0) < 1 } {
49                if start_time.elapsed().as_millis() > 50 {
50                    unsafe {
51                        tcsetattr(STDIN_FILENO, TCSANOW, &old_attributes);
52                    }
53                    return false;
54                }
55            }
56            let mut byte = 0;
57            unsafe {
58                read(STDIN_FILENO, &mut byte as *mut _ as *mut c_void, 1);
59            }
60            buf.push(byte);
61            if buf.starts_with(&[0x1B, b'[', b'?']) && buf.ends_with(b"c") {
62                for attribute in buf[3..(buf.len() - 1)].split(|x| *x == b';') {
63                    if attribute == [b'4'] {
64                        unsafe {
65                            tcsetattr(STDIN_FILENO, TCSANOW, &old_attributes);
66                        }
67                        return true;
68                    }
69                }
70            }
71        }
72    }
73}
74
75impl Default for SixelBackend {
76    fn default() -> Self {
77        Self::new()
78    }
79}
80
81impl super::ImageBackend for SixelBackend {
82    #[allow(clippy::map_entry)]
83    fn add_image(&self, lines: Vec<String>, image: &DynamicImage, colors: usize) -> Result<String> {
84        let tty_size = unsafe { get_dimensions() };
85        let cw = tty_size.ws_xpixel / tty_size.ws_col;
86        let lh = tty_size.ws_ypixel / tty_size.ws_row;
87        let width_ratio = 1.0 / cw as f64;
88        let height_ratio = 1.0 / lh as f64;
89
90        // resize image to fit the text height with the Lanczos3 algorithm
91        let image = image.resize(
92            u32::MAX,
93            (lines.len() as f64 / height_ratio) as u32,
94            FilterType::Lanczos3,
95        );
96        let image_columns = width_ratio * image.width() as f64;
97        let image_rows = height_ratio * image.height() as f64;
98
99        let rgba_image = image.to_rgba8(); // convert the image to rgba samples
100        let flat_samples = rgba_image.as_flat_samples();
101        let mut rgba_image = rgba_image.clone();
102        // reduce the amount of colors using dithering
103        let pixels = flat_samples
104            .image_slice()
105            .context("Error while slicing the image")?;
106        colorops::dither(&mut rgba_image, &NeuQuant::new(10, colors, pixels));
107
108        let rgb_image = ImageBuffer::from_fn(rgba_image.width(), rgba_image.height(), |x, y| {
109            let rgba_pixel = rgba_image.get_pixel(x, y);
110            let mut rgb_pixel = rgba_pixel.to_rgb();
111            for subpixel in &mut rgb_pixel.0 {
112                *subpixel = (*subpixel as f32 / 255.0 * rgba_pixel[3] as f32) as u8;
113            }
114            rgb_pixel
115        });
116
117        let mut image_data = Vec::<u8>::new();
118        image_data.extend(b"\x1BPq"); // start sixel data
119        image_data.extend(format!("\"1;1;{};{}", image.width(), image.height()).as_bytes());
120
121        let mut colors = std::collections::HashMap::<Rgb<u8>, u8>::new();
122        // subtract 1 -> divide -> add 1 to round up the integer division
123        for i in 0..((rgb_image.height() - 1) / 6 + 1) {
124            let sixel_row = rgb_image.view(
125                0,
126                i * 6,
127                rgb_image.width(),
128                std::cmp::min(6, rgb_image.height() - i * 6),
129            );
130            for (_, _, pixel) in sixel_row.pixels() {
131                if !colors.contains_key(&pixel) {
132                    // sixel uses percentages for rgb values
133                    let color_multiplier = 100.0 / 255.0;
134                    image_data.extend(
135                        format!(
136                            "#{};2;{};{};{}",
137                            colors.len(),
138                            (pixel[0] as f32 * color_multiplier) as u32,
139                            (pixel[1] as f32 * color_multiplier) as u32,
140                            (pixel[2] as f32 * color_multiplier) as u32
141                        )
142                        .as_bytes(),
143                    );
144                    colors.insert(pixel, colors.len() as u8);
145                }
146            }
147            for (color, color_index) in &colors {
148                let mut sixel_samples = vec![0; sixel_row.width() as usize];
149                sixel_samples.resize(sixel_row.width() as usize, 0);
150                for (x, y, pixel) in sixel_row.pixels() {
151                    if color == &pixel {
152                        sixel_samples[x as usize] |= 1 << y;
153                    }
154                }
155                image_data.extend(format!("#{color_index}").bytes());
156                image_data.extend(sixel_samples.iter().map(|x| x + 0x3F));
157                image_data.push(b'$');
158            }
159            image_data.push(b'-');
160        }
161        image_data.extend(b"\x1B\\");
162
163        image_data.extend(format!("\x1B[{}A", image_rows as u32 - 1).as_bytes()); // move cursor to top-left corner
164        image_data.extend(format!("\x1B[{}C", image_columns as u32 + 1).as_bytes()); // move cursor to top-right corner of image
165        let mut i = 0;
166        for line in &lines {
167            image_data.extend(format!("\x1B[s{line}\x1B[u\x1B[1B").as_bytes());
168            i += 1;
169        }
170        image_data
171            .extend(format!("\n\x1B[{}B", lines.len().max(image_rows as usize) - i).as_bytes()); // move cursor to end of image
172
173        Ok(String::from_utf8(image_data)?)
174    }
175}
onefetch_image/sixel.rs

onefetch_image/
sixel.rs
