feat: make HTML export self contained (#575)

#566 did the heavy work to allow HTML exports but the one thing missing
is that images were still referenced on their external paths, which
caused 2 issues:

* Files were not redistributable unless you included images and fixed
their paths.
* Generated images (e.g. mermaid diagrams) were likely pointing to a
temporary directory so they'd be lost.

This changes that so HTML exports are now fully self contained, using
`data:...` notation to inline images within the HTML.

.github/workflows/merge.yaml

@@ -45,7 +45,7 @@ jobs:
           source ./.venv/bin/activate
           uv pip install weasyprint
 
-      - name: Export demo presentation as PDF
+      - name: Export demo presentation as PDF and HTML
         run: |
           cat >/tmp/config.yaml <<EOL
           export:
@@ -54,7 +54,8 @@ jobs:
               columns: 135
           EOL
           source ./.venv/bin/activate
-          cargo run -- -e -c /tmp/config.yaml examples/demo.md
+          cargo run -- --export-pdf -c /tmp/config.yaml examples/demo.md
+          cargo run -- --export-html -c /tmp/config.yaml examples/demo.md
 
   nix-flake:
     name: Validate nix flake

src/export/output.rs

@@ -8,15 +8,11 @@ use crate::{
     presentation::Slide,
     render::{engine::RenderEngine, properties::WindowSize},
     terminal::{
-        image::{
+        image::printer::TerminalImage,
-            Image, ImageSource,
-            printer::{ImageProperties, TerminalImage},
-        },
         virt::{TerminalGrid, VirtualTerminal},
     },
     tools::ThirdPartyTools,
 };
-use image::{ImageEncoder, codecs::png::PngEncoder};
 use std::{
     fs, io,
     path::{Path, PathBuf},
@@ -37,7 +33,7 @@ struct HtmlSlide {
 }
 
 impl HtmlSlide {
-    fn new(grid: TerminalGrid, content_manager: &mut ContentManager) -> Result<Self, ExportError> {
+    fn new(grid: TerminalGrid) -> Result<Self, ExportError> {
         let mut rows = Vec::new();
         rows.push(String::from("<div class=\"container\">"));
         for (y, row) in grid.rows.into_iter().enumerate() {
@@ -58,11 +54,11 @@ impl HtmlSlide {
                     other => current_string.push(other),
                 }
                 if let Some(image) = grid.images.get(&(y as u16, x as u16)) {
-                    let image_path = content_manager.persist_image(&image.image)?;
+                    let TerminalImage::Raw(raw_image) = image.image.image() else { panic!("not in raw image mode") };
-                    let image_path_str = image_path.display();
+                    let image_contents = raw_image.to_inline_html();
                     let width_pixels = (image.width_columns as f64 * FONT_SIZE as f64 * FONT_SIZE_WIDTH).ceil();
                     let image_tag = format!(
-                        "<img width=\"{width_pixels}\" src=\"file://{image_path_str}\" style=\"position: absolute\" />"
+                        "<img width=\"{width_pixels}\" src=\"{image_contents}\" style=\"position: absolute\" />"
                     );
                     current_string.push_str(&image_tag);
                 }
@@ -86,35 +82,11 @@ impl HtmlSlide {
 
 pub(crate) struct ContentManager {
     output_directory: OutputDirectory,
-    image_count: usize,
 }
 
 impl ContentManager {
     pub(crate) fn new(output_directory: OutputDirectory) -> Self {
-        Self { output_directory, image_count: 0 }
+        Self { output_directory }
-    }
-
-    fn persist_image(&mut self, image: &Image) -> Result<PathBuf, ExportError> {
-        match image.source.clone() {
-            ImageSource::Filesystem(path) => Ok(path),
-            ImageSource::Generated => {
-                let mut buffer = Vec::new();
-                let dimensions = image.image().dimensions();
-                let TerminalImage::Ascii(image) = image.image() else { panic!("not in ascii mode") };
-                let image = image.image();
-                PngEncoder::new(&mut buffer).write_image(
-                    image.as_bytes(),
-                    dimensions.0,
-                    dimensions.1,
-                    image.color().into(),
-                )?;
-                let name = format!("img-{}.png", self.image_count);
-                let path = self.output_directory.path().join(name);
-                fs::write(&path, buffer)?;
-                self.image_count += 1;
-                Ok(path)
-            }
-        }
     }
 
     fn persist_file(&self, name: &str, data: &[u8]) -> io::Result<PathBuf> {
@@ -155,7 +127,7 @@ impl ExportRenderer {
         engine.render(slide.iter_operations())?;
 
         let grid = terminal.into_contents();
-        let slide = HtmlSlide::new(grid, &mut self.content_manager)?;
+        let slide = HtmlSlide::new(grid)?;
         if self.background_color.is_none() {
             self.background_color.clone_from(&slide.background_color);
         }

src/main.rs

@@ -293,8 +293,8 @@ impl CoreComponents {
     }
 
     fn select_graphics_mode(cli: &Cli, config: &Config) -> GraphicsMode {
-        if cli.export_pdf {
+        if cli.export_pdf | cli.export_html {
-            GraphicsMode::AsciiBlocks
+            GraphicsMode::Raw
         } else {
             let protocol = cli.image_protocol.as_ref().unwrap_or(&config.defaults.image_protocol);
             match GraphicsMode::try_from(protocol) {

src/terminal/image/mod.rs

@@ -1,7 +1,6 @@
+use self::printer::{ImageProperties, TerminalImage};
 use image::DynamicImage;
 use protocols::ascii::AsciiImage;
-
-use self::printer::{ImageProperties, TerminalImage};
 use std::{
     fmt::Debug,
     ops::Deref,
@@ -43,6 +42,7 @@ impl Image {
                     TerminalImage::Ascii(image) => image.clone(),
                     TerminalImage::Kitty(image) => DynamicImage::from(image.as_rgba8()).into(),
                     TerminalImage::Iterm(image) => DynamicImage::from(image.as_rgba8()).into(),
+                    TerminalImage::Raw(_) => unreachable!("raw is only used for exports"),
                     #[cfg(feature = "sixel")]
                     TerminalImage::Sixel(image) => DynamicImage::from(image.as_rgba8()).into(),
                 };

src/terminal/image/printer.rs

@@ -4,6 +4,7 @@ use super::{
         ascii::{AsciiImage, AsciiPrinter},
         iterm::{ItermImage, ItermPrinter},
         kitty::{KittyImage, KittyMode, KittyPrinter},
+        raw::{RawImage, RawPrinter},
     },
 };
 use crate::{
@@ -54,6 +55,7 @@ pub(crate) enum TerminalImage {
     Kitty(KittyImage),
     Iterm(ItermImage),
     Ascii(AsciiImage),
+    Raw(RawImage),
     #[cfg(feature = "sixel")]
     Sixel(super::protocols::sixel::SixelImage),
 }
@@ -64,6 +66,7 @@ impl ImageProperties for TerminalImage {
             Self::Kitty(image) => image.dimensions(),
             Self::Iterm(image) => image.dimensions(),
             Self::Ascii(image) => image.dimensions(),
+            Self::Raw(image) => image.dimensions(),
             #[cfg(feature = "sixel")]
             Self::Sixel(image) => image.dimensions(),
         }
@@ -74,6 +77,7 @@ pub enum ImagePrinter {
     Kitty(KittyPrinter),
     Iterm(ItermPrinter),
     Ascii(AsciiPrinter),
+    Raw(RawPrinter),
     Null,
     #[cfg(feature = "sixel")]
     Sixel(super::protocols::sixel::SixelPrinter),
@@ -91,6 +95,7 @@ impl ImagePrinter {
             GraphicsMode::Kitty { mode, inside_tmux } => Self::new_kitty(mode, inside_tmux)?,
             GraphicsMode::Iterm2 => Self::new_iterm(),
             GraphicsMode::AsciiBlocks => Self::new_ascii(),
+            GraphicsMode::Raw => Self::new_raw(),
             #[cfg(feature = "sixel")]
             GraphicsMode::Sixel => Self::new_sixel()?,
         };
@@ -109,6 +114,10 @@ impl ImagePrinter {
         Self::Ascii(AsciiPrinter)
     }
 
+    fn new_raw() -> Self {
+        Self::Raw(RawPrinter)
+    }
+
     #[cfg(feature = "sixel")]
     fn new_sixel() -> Result<Self, CreatePrinterError> {
         Ok(Self::Sixel(super::protocols::sixel::SixelPrinter::new()?))
@@ -124,6 +133,7 @@ impl PrintImage for ImagePrinter {
             Self::Iterm(printer) => TerminalImage::Iterm(printer.register(spec)?),
             Self::Ascii(printer) => TerminalImage::Ascii(printer.register(spec)?),
             Self::Null => return Err(RegisterImageError::Unsupported),
+            Self::Raw(printer) => TerminalImage::Raw(printer.register(spec)?),
             #[cfg(feature = "sixel")]
             Self::Sixel(printer) => TerminalImage::Sixel(printer.register(spec)?),
         };
@@ -139,6 +149,7 @@ impl PrintImage for ImagePrinter {
             (Self::Iterm(printer), TerminalImage::Iterm(image)) => printer.print(image, options, terminal),
             (Self::Ascii(printer), TerminalImage::Ascii(image)) => printer.print(image, options, terminal),
             (Self::Null, _) => Ok(()),
+            (Self::Raw(printer), TerminalImage::Raw(image)) => printer.print(image, options, terminal),
             #[cfg(feature = "sixel")]
             (Self::Sixel(printer), TerminalImage::Sixel(image)) => printer.print(image, options, terminal),
             _ => Err(PrintImageError::Unsupported),
@@ -165,6 +176,7 @@ impl fmt::Debug for ImageRegistry {
             ImagePrinter::Iterm(_) => "Iterm",
             ImagePrinter::Ascii(_) => "Ascii",
             ImagePrinter::Null => "Null",
+            ImagePrinter::Raw(_) => "Raw",
             #[cfg(feature = "sixel")]
             ImagePrinter::Sixel(_) => "Sixel",
         };

src/terminal/image/protocols/ascii.rs

@@ -36,10 +36,6 @@ impl AsciiImage {
             cached_sizes.insert(cache_key, image.into_rgba8());
         }
     }
-
-    pub(crate) fn image(&self) -> &DynamicImage {
-        &self.inner.image
-    }
 }
 
 impl ImageProperties for AsciiImage {

src/terminal/image/protocols/mod.rs

@@ -1,5 +1,6 @@
 pub(crate) mod ascii;
 pub(crate) mod iterm;
 pub(crate) mod kitty;
+pub(crate) mod raw;
 #[cfg(feature = "sixel")]
 pub(crate) mod sixel;

src/terminal/image/protocols/raw.rs

@@ -0,0 +1,61 @@
+use crate::terminal::{
+    image::printer::{ImageProperties, ImageSpec, PrintImage, PrintImageError, PrintOptions, RegisterImageError},
+    printer::TerminalIo,
+};
+use base64::{Engine, engine::general_purpose::STANDARD};
+use image::{GenericImageView, ImageEncoder, ImageFormat, codecs::png::PngEncoder};
+use std::fs;
+
+pub(crate) struct RawImage {
+    contents: Vec<u8>,
+    format: ImageFormat,
+    width: u32,
+    height: u32,
+}
+
+impl RawImage {
+    pub(crate) fn to_inline_html(&self) -> String {
+        let mime_type = self.format.to_mime_type();
+        let data = STANDARD.encode(&self.contents);
+        format!("data:{mime_type};base64,{data}")
+    }
+}
+
+impl ImageProperties for RawImage {
+    fn dimensions(&self) -> (u32, u32) {
+        (self.width, self.height)
+    }
+}
+
+pub(crate) struct RawPrinter;
+
+impl PrintImage for RawPrinter {
+    type Image = RawImage;
+
+    fn register(&self, spec: ImageSpec) -> Result<Self::Image, RegisterImageError> {
+        let image = match spec {
+            ImageSpec::Generated(image) => {
+                let mut contents = Vec::new();
+                let encoder = PngEncoder::new(&mut contents);
+                let (width, height) = image.dimensions();
+                encoder.write_image(image.as_bytes(), width, height, image.color().into())?;
+                RawImage { contents, format: ImageFormat::Png, width, height }
+            }
+            ImageSpec::Filesystem(path) => {
+                let contents = fs::read(path)?;
+                let format = image::guess_format(&contents)?;
+                let image = image::load_from_memory_with_format(&contents, format)?;
+                let (width, height) = image.dimensions();
+                RawImage { contents, format, width, height }
+            }
+        };
+        Ok(image)
+    }
+
+    fn print<T>(&self, _image: &Self::Image, _options: &PrintOptions, _terminal: &mut T) -> Result<(), PrintImageError>
+    where
+        T: TerminalIo,
+    {
+        Err(PrintImageError::Other("raw images can't be printed".into()))
+    }
+}

src/terminal/mod.rs

@@ -15,6 +15,7 @@ pub enum GraphicsMode {
         inside_tmux: bool,
     },
     AsciiBlocks,
+    Raw,
     #[cfg(feature = "sixel")]
     Sixel,
 }