typst/crates/typst-svg/src/image.rs

use base64::Engine;
use ecow::{eco_format, EcoString};
use typst::layout::{Abs, Axes};
use typst::visualize::{Image, ImageFormat, RasterFormat, VectorFormat};

use crate::SVGRenderer;

impl SVGRenderer {
    /// Render an image element.
    pub(super) fn render_image(&mut self, image: &Image, size: &Axes<Abs>) {
        let url = convert_image_to_base64_url(image);
        self.xml.start_element("image");
        self.xml.write_attribute("xlink:href", &url);
        self.xml.write_attribute("width", &size.x.to_pt());
        self.xml.write_attribute("height", &size.y.to_pt());
        self.xml.write_attribute("preserveAspectRatio", "none");
        self.xml.end_element();
    }
}

/// Encode an image into a data URL. The format of the URL is
/// `data:image/{format};base64,`.
#[comemo::memoize]
pub fn convert_image_to_base64_url(image: &Image) -> EcoString {
    let format = match image.format() {
        ImageFormat::Raster(f) => match f {
            RasterFormat::Png => "png",
            RasterFormat::Jpg => "jpeg",
            RasterFormat::Gif => "gif",
        },
        ImageFormat::Vector(f) => match f {
            VectorFormat::Svg => "svg+xml",
        },
    };

    let mut url = eco_format!("data:image/{format};base64,");
    let data = base64::engine::general_purpose::STANDARD.encode(image.data());
    url.push_str(&data);
    url
}