88 lines
3.2 KiB
Rust
88 lines
3.2 KiB
Rust
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//! Image → terminal-art conversion, used wherever the player shows pictures
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//! (artist tiles, release covers, now-playing).
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//!
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//! The format is "half-block art": each terminal cell renders `▀` with the
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//! foreground colored as the top pixel and the background as the bottom
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//! pixel, giving 2 vertical pixels per cell. This needs no terminal image
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//! protocol (sixel/kitty), so it works everywhere crossterm does, and it
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//! looks far better than glyph-luminance ASCII at tile sizes. The UI layer
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//! converts `ArtImage` cells into styled spans.
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use anyhow::{Context as _, Result};
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/// Cache key for the shared artwork cache: the same image can be cached at
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/// several cell sizes (grid tile vs page header).
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pub fn cache_key(url: &str, width_cells: u16, height_cells: u16) -> String {
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format!("{url}#{width_cells}x{height_cells}")
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}
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/// Decoded, cell-sized art. `pixels` holds `width_cells * height_cells * 2`
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/// RGB triples, row-major, two pixel rows per cell row (top, then bottom).
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct ArtImage {
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pub width_cells: u16,
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pub height_cells: u16,
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pixels: Vec<[u8; 3]>,
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}
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impl ArtImage {
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/// Top and bottom pixel of the cell at (column, cell row).
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pub fn cell(&self, x: u16, y: u16) -> ([u8; 3], [u8; 3]) {
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let width = self.width_cells as usize;
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let top = (y as usize * 2) * width + x as usize;
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let bottom = (y as usize * 2 + 1) * width + x as usize;
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(self.pixels[top], self.pixels[bottom])
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}
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}
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/// Decode image bytes (jpeg/png/webp/gif/bmp) and scale them to fill a
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/// `width_cells` × `height_cells` terminal area, center-cropping overflow
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/// like CSS object-fit: cover.
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pub fn decode_to_cells(bytes: &[u8], width_cells: u16, height_cells: u16) -> Result<ArtImage> {
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let width_px = u32::from(width_cells.max(1));
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let height_px = u32::from(height_cells.max(1)) * 2;
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let image = image::load_from_memory(bytes).context("unsupported or corrupt image")?;
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let image = image
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.resize_to_fill(width_px, height_px, image::imageops::FilterType::Triangle)
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.into_rgb8();
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let pixels = image.pixels().map(|p| p.0).collect();
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Ok(ArtImage {
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width_cells: width_cells.max(1),
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height_cells: height_cells.max(1),
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pixels,
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})
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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fn png_2x2() -> Vec<u8> {
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// red, green / blue, white
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let mut img = image::RgbImage::new(2, 2);
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img.put_pixel(0, 0, image::Rgb([255, 0, 0]));
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img.put_pixel(1, 0, image::Rgb([0, 255, 0]));
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img.put_pixel(0, 1, image::Rgb([0, 0, 255]));
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img.put_pixel(1, 1, image::Rgb([255, 255, 255]));
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let mut out = std::io::Cursor::new(Vec::new());
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image::DynamicImage::ImageRgb8(img)
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.write_to(&mut out, image::ImageFormat::Png)
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.unwrap();
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out.into_inner()
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}
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#[test]
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fn decodes_to_requested_cell_grid() {
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let art = decode_to_cells(&png_2x2(), 2, 1).unwrap();
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assert_eq!((art.width_cells, art.height_cells), (2, 1));
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let (top, bottom) = art.cell(0, 0);
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assert_eq!(top, [255, 0, 0]);
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assert_eq!(bottom, [0, 0, 255]);
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}
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#[test]
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fn rejects_garbage() {
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assert!(decode_to_cells(b"not an image", 4, 4).is_err());
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}
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}
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