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use std::sync::Arc;
use image::imageops::FilterType;
use image::{GenericImageView, Rgba};
use tiny_skia as sk;
use typst_library::layout::Size;
use typst_library::visualize::{Image, ImageKind};
use crate::{AbsExt, State};
/// Render a raster or SVG image into the canvas.
pub fn render_image(
canvas: &mut sk::Pixmap,
state: State,
image: &Image,
size: Size,
) -> Option<()> {
let ts = state.transform;
let view_width = size.x.to_f32();
let view_height = size.y.to_f32();
// For better-looking output, resize `image` to its final size before
// painting it to `canvas`. For the math, see:
// https://github.com/typst/typst/issues/1404#issuecomment-1598374652
let theta = f32::atan2(-ts.kx, ts.sx);
// To avoid division by 0, choose the one of { sin, cos } that is
// further from 0.
let prefer_sin = theta.sin().abs() > std::f32::consts::FRAC_1_SQRT_2;
let scale_x =
f32::abs(if prefer_sin { ts.kx / theta.sin() } else { ts.sx / theta.cos() });
let aspect = (image.width() as f32) / (image.height() as f32);
let w = (scale_x * view_width.max(aspect * view_height)).ceil() as u32;
let h = ((w as f32) / aspect).ceil() as u32;
let pixmap = scaled_texture(image, w, h)?;
let paint_scale_x = view_width / pixmap.width() as f32;
let paint_scale_y = view_height / pixmap.height() as f32;
let paint = sk::Paint {
shader: sk::Pattern::new(
(*pixmap).as_ref(),
sk::SpreadMode::Pad,
sk::FilterQuality::Nearest,
1.0,
sk::Transform::from_scale(paint_scale_x, paint_scale_y),
),
..Default::default()
};
let rect = sk::Rect::from_xywh(0.0, 0.0, view_width, view_height)?;
canvas.fill_rect(rect, &paint, ts, state.mask);
Some(())
}
/// Prepare a texture for an image at a scaled size.
#[comemo::memoize]
fn scaled_texture(image: &Image, w: u32, h: u32) -> Option<Arc<sk::Pixmap>> {
let mut pixmap = sk::Pixmap::new(w, h)?;
match image.kind() {
ImageKind::Raster(raster) => {
let downscale = w < raster.width();
let filter =
if downscale { FilterType::Lanczos3 } else { FilterType::CatmullRom };
let buf = raster.dynamic().resize(w, h, filter);
for ((_, _, src), dest) in buf.pixels().zip(pixmap.pixels_mut()) {
let Rgba([r, g, b, a]) = src;
*dest = sk::ColorU8::from_rgba(r, g, b, a).premultiply();
}
}
// Safety: We do not keep any references to tree nodes beyond the scope
// of `with`.
ImageKind::Svg(svg) => {
let tree = svg.tree();
let ts = tiny_skia::Transform::from_scale(
w as f32 / tree.size().width(),
h as f32 / tree.size().height(),
);
resvg::render(tree, ts, &mut pixmap.as_mut())
}
}
Some(Arc::new(pixmap))
}
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