perf: cache ascii image resizes

Cargo.toml

@@ -43,8 +43,7 @@ vte = "0.15"
 rstest = { version = "0.25", default-features = false }
 
 [features]
-# TODO
-default = ["sixel"]
+default = []
 sixel = ["sixel-rs"]
 
 [profile.dev]

src/terminal/image/protocols/ascii.rs

@@ -5,26 +5,34 @@ use crate::{
         printer::{TerminalCommand, TerminalIo},
     },
 };
-use image::{DynamicImage, GenericImageView, Pixel, Rgba, imageops::FilterType};
+use image::{DynamicImage, GenericImageView, Pixel, Rgba, RgbaImage, imageops::FilterType};
 use itertools::Itertools;
-use std::{fs, ops::Deref, sync::Arc};
+use std::{
+    collections::HashMap,
+    fs,
+    ops::Deref,
+    sync::{Arc, Mutex},
+};
 
 const TOP_CHAR: &str = "▀";
 const BOTTOM_CHAR: &str = "▄";
 
 #[derive(Clone)]
-pub(crate) struct AsciiImage(Arc<DynamicImage>);
+pub(crate) struct AsciiImage {
+    image: Arc<DynamicImage>,
+    cached_sizes: Arc<Mutex<HashMap<(u16, u16), RgbaImage>>>,
+}
 
 impl ImageProperties for AsciiImage {
     fn dimensions(&self) -> (u32, u32) {
-        self.0.dimensions()
+        self.image.dimensions()
     }
 }
 
 impl From<DynamicImage> for AsciiImage {
     fn from(image: DynamicImage) -> Self {
         let image = image.into_rgba8();
-        Self(Arc::new(image.into()))
+        Self { image: Arc::new(image.into()), cached_sizes: Default::default() }
     }
 }
 
@@ -32,7 +40,7 @@ impl Deref for AsciiImage {
     type Target = DynamicImage;
 
     fn deref(&self) -> &Self::Target {
-        &self.0
+        &self.image
     }
 }
 
@@ -74,18 +82,29 @@ impl PrintImage for AsciiPrinter {
                 image::load_from_memory(&contents)?
             }
         };
-        Ok(AsciiImage(image.into()))
+        Ok(AsciiImage::from(image))
     }
 
     fn print<T>(&self, image: &Self::Image, options: &PrintOptions, terminal: &mut T) -> Result<(), PrintImageError>
     where
         T: TerminalIo,
     {
+        let columns = options.columns;
+        let rows = options.rows * 2;
+        let mut cached_sizes = image.cached_sizes.lock().unwrap();
+        // lookup on cache/resize the image and store it in cache
+        let cache_key = (columns, rows);
+        let image = match cached_sizes.get(&cache_key) {
+            Some(image) => image,
+            None => {
+                let image = image.image.resize_exact(columns as u32, rows as u32, FilterType::Triangle);
+                cached_sizes.insert(cache_key, image.into_rgba8());
+                cached_sizes.get(&cache_key).unwrap()
+            }
+        };
         // The strategy here is taken from viuer: use half vertical ascii blocks in combination
         // with foreground/background colors to fit 2 vertical pixels per cell. That is, cell (x, y)
         // will contain the pixels at (x, y) and (x, y + 1) combined.
-        let image = image.0.resize_exact(options.columns as u32, 2 * options.rows as u32, FilterType::Triangle);
-        let image = image.into_rgba8();
         let default_background = options.background_color.map(Color::from);
 
         // Iterate pixel rows in pairs to be able to merge both pixels in a single iteration.