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use std::collections::HashMap;
use std::io::Cursor;
use image::{DynamicImage, GenericImageView, Rgba};
use pdf_writer::{Chunk, Filter, Finish, Ref};
use typst::util::Deferred;
use typst::visualize::{
ColorSpace, Image, ImageKind, RasterFormat, RasterImage, SvgImage,
};
use crate::{deflate, PdfContext};
/// Creates a new PDF image from the given image.
///
/// Also starts the deferred encoding of the image.
#[comemo::memoize]
pub fn deferred_image(image: Image) -> Deferred<EncodedImage> {
Deferred::new(move || match image.kind() {
ImageKind::Raster(raster) => {
let raster = raster.clone();
let (width, height) = (image.width(), image.height());
let (data, filter, has_color) = encode_raster_image(&raster);
let icc = raster.icc().map(deflate);
let alpha =
raster.dynamic().color().has_alpha().then(|| encode_alpha(&raster));
EncodedImage::Raster { data, filter, has_color, width, height, icc, alpha }
}
ImageKind::Svg(svg) => EncodedImage::Svg(encode_svg(svg)),
})
}
/// Embed all used images into the PDF.
#[tracing::instrument(skip_all)]
pub(crate) fn write_images(ctx: &mut PdfContext) {
for (i, _) in ctx.image_map.items().enumerate() {
let handle = ctx.image_deferred_map.get(&i).unwrap();
match handle.wait() {
EncodedImage::Raster {
data,
filter,
has_color,
width,
height,
icc,
alpha,
} => {
let image_ref = ctx.alloc.bump();
ctx.image_refs.push(image_ref);
let mut image = ctx.pdf.image_xobject(image_ref, data);
image.filter(*filter);
image.width(*width as i32);
image.height(*height as i32);
image.bits_per_component(8);
let mut icc_ref = None;
let space = image.color_space();
if icc.is_some() {
let id = ctx.alloc.bump();
space.icc_based(id);
icc_ref = Some(id);
} else if *has_color {
ctx.colors.write(ColorSpace::Srgb, space, &mut ctx.alloc);
} else {
ctx.colors.write(ColorSpace::D65Gray, space, &mut ctx.alloc);
}
// Add a second gray-scale image containing the alpha values if
// this image has an alpha channel.
if let Some((alpha_data, alpha_filter)) = alpha {
let mask_ref = ctx.alloc.bump();
image.s_mask(mask_ref);
image.finish();
let mut mask = ctx.pdf.image_xobject(mask_ref, alpha_data);
mask.filter(*alpha_filter);
mask.width(*width as i32);
mask.height(*height as i32);
mask.color_space().device_gray();
mask.bits_per_component(8);
} else {
image.finish();
}
if let (Some(icc), Some(icc_ref)) = (icc, icc_ref) {
let mut stream = ctx.pdf.icc_profile(icc_ref, icc);
stream.filter(Filter::FlateDecode);
if *has_color {
stream.n(3);
stream.alternate().srgb();
} else {
stream.n(1);
stream.alternate().d65_gray();
}
}
}
EncodedImage::Svg(chunk) => {
let mut map = HashMap::new();
chunk.renumber_into(&mut ctx.pdf, |old| {
*map.entry(old).or_insert_with(|| ctx.alloc.bump())
});
ctx.image_refs.push(map[&Ref::new(1)]);
}
}
}
}
/// Encode an image with a suitable filter and return the data, filter and
/// whether the image has color.
///
/// Skips the alpha channel as that's encoded separately.
#[tracing::instrument(skip_all)]
fn encode_raster_image(image: &RasterImage) -> (Vec<u8>, Filter, bool) {
let dynamic = image.dynamic();
match (image.format(), dynamic) {
// 8-bit gray JPEG.
(RasterFormat::Jpg, DynamicImage::ImageLuma8(_)) => {
let mut data = Cursor::new(vec![]);
dynamic.write_to(&mut data, image::ImageFormat::Jpeg).unwrap();
(data.into_inner(), Filter::DctDecode, false)
}
// 8-bit RGB JPEG (CMYK JPEGs get converted to RGB earlier).
(RasterFormat::Jpg, DynamicImage::ImageRgb8(_)) => {
let mut data = Cursor::new(vec![]);
dynamic.write_to(&mut data, image::ImageFormat::Jpeg).unwrap();
(data.into_inner(), Filter::DctDecode, true)
}
// TODO: Encode flate streams with PNG-predictor?
// 8-bit gray PNG.
(RasterFormat::Png, DynamicImage::ImageLuma8(luma)) => {
let data = deflate(luma.as_raw());
(data, Filter::FlateDecode, false)
}
// Anything else (including Rgb(a) PNGs).
(_, buf) => {
let (width, height) = buf.dimensions();
let mut pixels = Vec::with_capacity(3 * width as usize * height as usize);
for (_, _, Rgba([r, g, b, _])) in buf.pixels() {
pixels.push(r);
pixels.push(g);
pixels.push(b);
}
let data = deflate(&pixels);
(data, Filter::FlateDecode, true)
}
}
}
/// Encode an image's alpha channel if present.
#[tracing::instrument(skip_all)]
fn encode_alpha(raster: &RasterImage) -> (Vec<u8>, Filter) {
let pixels: Vec<_> = raster
.dynamic()
.pixels()
.map(|(_, _, Rgba([_, _, _, a]))| a)
.collect();
(deflate(&pixels), Filter::FlateDecode)
}
/// Encode an SVG into a chunk of PDF objects.
///
/// The main XObject will have ID 1.
#[tracing::instrument(skip_all)]
fn encode_svg(svg: &SvgImage) -> Chunk {
let mut chunk = Chunk::new();
// Safety: We do not keep any references to tree nodes beyond the
// scope of `with`.
unsafe {
svg.with(|tree| {
svg2pdf::convert_tree_into(
tree,
svg2pdf::Options::default(),
&mut chunk,
Ref::new(1),
);
});
}
chunk
}
/// A pre-encoded image.
pub enum EncodedImage {
/// A pre-encoded rasterized image.
Raster {
/// The raw, pre-deflated image data.
data: Vec<u8>,
/// The filter to use for the image.
filter: Filter,
/// Whether the image has color.
has_color: bool,
/// The image's width.
width: u32,
/// The image's height.
height: u32,
/// The image's ICC profile, pre-deflated, if any.
icc: Option<Vec<u8>>,
/// The alpha channel of the image, pre-deflated, if any.
alpha: Option<(Vec<u8>, Filter)>,
},
/// A vector graphic.
///
/// The chunk is the SVG converted to PDF objects.
Svg(Chunk),
}
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