mirror of https://github.com/stelzo/typst.git
685 lines
24 KiB
Rust
685 lines
24 KiB
Rust
//! Exporting into PDF documents.
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use std::cmp::Eq;
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use std::collections::{BTreeMap, HashMap, HashSet};
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use std::hash::Hash;
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use std::rc::Rc;
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use image::{DynamicImage, GenericImageView, ImageFormat, ImageResult, Rgba};
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use miniz_oxide::deflate;
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use pdf_writer::{
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ActionType, AnnotationType, CidFontType, ColorSpace, Content, Filter, FontFlags,
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Name, PdfWriter, Rect, Ref, Str, SystemInfo, UnicodeCmap,
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};
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use ttf_parser::{name_id, GlyphId, Tag};
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use super::subset;
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use crate::color::Color;
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use crate::font::{find_name, FaceId, FontStore};
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use crate::geom::{self, Em, Length, Size};
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use crate::image::{Image, ImageId, ImageStore};
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use crate::layout::{Element, Frame, Geometry, Paint};
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use crate::Context;
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/// Export a collection of frames into a PDF document.
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///
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/// This creates one page per frame. In addition to the frames, you need to pass
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/// in the context used during compilation such that things like fonts and
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/// images can be included in the PDF.
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///
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/// Returns the raw bytes making up the PDF document.
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pub fn pdf(ctx: &Context, frames: &[Rc<Frame>]) -> Vec<u8> {
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PdfExporter::new(ctx, frames).write()
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}
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struct PdfExporter<'a> {
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writer: PdfWriter,
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refs: Refs,
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frames: &'a [Rc<Frame>],
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fonts: &'a FontStore,
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images: &'a ImageStore,
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glyphs: HashMap<FaceId, HashSet<u16>>,
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font_map: Remapper<FaceId>,
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image_map: Remapper<ImageId>,
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}
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impl<'a> PdfExporter<'a> {
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fn new(ctx: &'a Context, frames: &'a [Rc<Frame>]) -> Self {
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let mut glyphs = HashMap::<FaceId, HashSet<u16>>::new();
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let mut font_map = Remapper::new();
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let mut image_map = Remapper::new();
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let mut alpha_masks = 0;
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for frame in frames {
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for (_, element) in frame.elements() {
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match *element {
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Element::Text(ref text) => {
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font_map.insert(text.face_id);
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let set = glyphs.entry(text.face_id).or_default();
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set.extend(text.glyphs.iter().map(|g| g.id));
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}
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Element::Geometry(_, _) => {}
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Element::Image(id, _) => {
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let img = ctx.images.get(id);
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if img.buf.color().has_alpha() {
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alpha_masks += 1;
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}
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image_map.insert(id);
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}
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Element::Link(_, _) => {}
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}
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}
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}
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let mut writer = PdfWriter::new(1, 7);
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writer.set_indent(2);
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Self {
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writer,
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refs: Refs::new(frames.len(), font_map.len(), image_map.len(), alpha_masks),
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frames,
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fonts: &ctx.fonts,
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images: &ctx.images,
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glyphs,
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font_map,
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image_map,
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}
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}
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fn write(mut self) -> Vec<u8> {
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self.write_structure();
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self.write_pages();
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self.write_fonts();
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self.write_images();
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self.writer.finish(self.refs.catalog)
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}
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fn write_structure(&mut self) {
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// The document catalog.
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self.writer.catalog(self.refs.catalog).pages(self.refs.page_tree);
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// The root page tree.
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let mut pages = self.writer.pages(self.refs.page_tree);
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pages.kids(self.refs.pages());
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let mut resources = pages.resources();
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let mut fonts = resources.fonts();
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for (refs, f) in self.refs.fonts().zip(self.font_map.pdf_indices()) {
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let name = format!("F{}", f);
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fonts.pair(Name(name.as_bytes()), refs.type0_font);
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}
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drop(fonts);
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let mut images = resources.x_objects();
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for (id, im) in self.refs.images().zip(self.image_map.pdf_indices()) {
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let name = format!("Im{}", im);
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images.pair(Name(name.as_bytes()), id);
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}
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drop(images);
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drop(resources);
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drop(pages);
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// The page objects (non-root nodes in the page tree).
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for ((page_id, content_id), page) in
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self.refs.pages().zip(self.refs.contents()).zip(self.frames)
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{
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let w = page.size.w.to_pt() as f32;
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let h = page.size.h.to_pt() as f32;
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let mut page_writer = self.writer.page(page_id);
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page_writer
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.parent(self.refs.page_tree)
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.media_box(Rect::new(0.0, 0.0, w, h));
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let mut annotations = page_writer.annotations();
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for (pos, element) in page.elements() {
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if let Element::Link(href, size) = element {
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let x = pos.x.to_pt() as f32;
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let y = (page.size.h - pos.y).to_pt() as f32;
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let w = size.w.to_pt() as f32;
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let h = size.h.to_pt() as f32;
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annotations
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.push()
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.subtype(AnnotationType::Link)
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.rect(Rect::new(x, y - h, x + w, y))
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.action()
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.action_type(ActionType::Uri)
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.uri(Str(href.as_bytes()));
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}
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}
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drop(annotations);
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page_writer.contents(content_id);
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}
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}
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fn write_pages(&mut self) {
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for (id, page) in self.refs.contents().zip(self.frames) {
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self.write_page(id, &page);
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}
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}
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fn write_page(&mut self, id: Ref, page: &'a Frame) {
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let mut content = Content::new();
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// We only write font switching actions when the used face changes. To
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// do that, we need to remember the active face.
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let mut face_id = None;
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let mut size = Length::zero();
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let mut fill: Option<Paint> = None;
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for (pos, element) in page.elements() {
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let x = pos.x.to_pt() as f32;
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let y = (page.size.h - pos.y).to_pt() as f32;
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match *element {
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Element::Text(ref text) => {
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if fill != Some(text.fill) {
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write_fill(&mut content, text.fill);
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fill = Some(text.fill);
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}
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let mut text_writer = content.text();
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// Then, also check if we need to issue a font switching
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// action.
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if face_id != Some(text.face_id) || text.size != size {
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face_id = Some(text.face_id);
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size = text.size;
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let name = format!("F{}", self.font_map.map(text.face_id));
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text_writer.font(Name(name.as_bytes()), size.to_pt() as f32);
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}
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let face = self.fonts.get(text.face_id);
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// Position the text.
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text_writer.matrix(1.0, 0.0, 0.0, 1.0, x, y);
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let mut positioned = text_writer.show_positioned();
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let mut adjustment = Em::zero();
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let mut encoded = vec![];
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// Write the glyphs with kerning adjustments.
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for glyph in &text.glyphs {
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adjustment += glyph.x_offset;
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if !adjustment.is_zero() {
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if !encoded.is_empty() {
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positioned.show(Str(&encoded));
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encoded.clear();
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}
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positioned.adjust(-adjustment.to_pdf());
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adjustment = Em::zero();
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}
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encoded.push((glyph.id >> 8) as u8);
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encoded.push((glyph.id & 0xff) as u8);
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if let Some(advance) = face.advance(glyph.id) {
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adjustment += glyph.x_advance - advance;
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}
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adjustment -= glyph.x_offset;
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}
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if !encoded.is_empty() {
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positioned.show(Str(&encoded));
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}
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}
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Element::Geometry(ref geometry, paint) => {
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content.save_state();
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match *geometry {
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Geometry::Rect(Size { w, h }) => {
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let w = w.to_pt() as f32;
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let h = h.to_pt() as f32;
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if w > 0.0 && h > 0.0 {
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write_fill(&mut content, paint);
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content.rect(x, y - h, w, h, false, true);
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}
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}
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Geometry::Ellipse(size) => {
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let path = geom::Path::ellipse(size);
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write_fill(&mut content, paint);
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write_path(&mut content, x, y, &path, false, true);
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}
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Geometry::Line(target, thickness) => {
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write_stroke(&mut content, paint, thickness.to_pt() as f32);
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content.path(true, false).move_to(x, y).line_to(
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x + target.x.to_pt() as f32,
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y - target.y.to_pt() as f32,
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);
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}
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Geometry::Path(ref path) => {
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write_fill(&mut content, paint);
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write_path(&mut content, x, y, path, false, true)
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}
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}
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content.restore_state();
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}
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Element::Image(id, Size { w, h }) => {
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let name = format!("Im{}", self.image_map.map(id));
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let w = w.to_pt() as f32;
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let h = h.to_pt() as f32;
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content.save_state();
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content.matrix(w, 0.0, 0.0, h, x, y - h);
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content.x_object(Name(name.as_bytes()));
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content.restore_state();
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}
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Element::Link(_, _) => {}
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}
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}
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self.writer.stream(id, &content.finish());
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}
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fn write_fonts(&mut self) {
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for (refs, face_id) in self.refs.fonts().zip(self.font_map.layout_indices()) {
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let glyphs = &self.glyphs[&face_id];
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let face = self.fonts.get(face_id);
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let ttf = face.ttf();
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let name = find_name(ttf.names(), name_id::POST_SCRIPT_NAME)
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.unwrap_or_else(|| "unknown".to_string());
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let base_font = format!("ABCDEF+{}", name);
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let base_font = Name(base_font.as_bytes());
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let cmap_name = Name(b"Custom");
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let system_info = SystemInfo {
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registry: Str(b"Adobe"),
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ordering: Str(b"Identity"),
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supplement: 0,
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};
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let mut flags = FontFlags::empty();
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flags.set(FontFlags::SERIF, name.contains("Serif"));
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flags.set(FontFlags::FIXED_PITCH, ttf.is_monospaced());
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flags.set(FontFlags::ITALIC, ttf.is_italic());
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flags.insert(FontFlags::SYMBOLIC);
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flags.insert(FontFlags::SMALL_CAP);
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let global_bbox = ttf.global_bounding_box();
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let bbox = Rect::new(
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face.to_em(global_bbox.x_min).to_pdf(),
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face.to_em(global_bbox.y_min).to_pdf(),
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face.to_em(global_bbox.x_max).to_pdf(),
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face.to_em(global_bbox.y_max).to_pdf(),
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);
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let italic_angle = ttf.italic_angle().unwrap_or(0.0);
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let ascender = face.ascender.to_pdf();
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let descender = face.descender.to_pdf();
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let cap_height = face.cap_height.to_pdf();
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let stem_v = 10.0 + 0.244 * (f32::from(ttf.weight().to_number()) - 50.0);
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// Check for the presence of CFF outlines to select the correct
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// CID-Font subtype.
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let subtype = match ttf
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.table_data(Tag::from_bytes(b"CFF "))
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.or(ttf.table_data(Tag::from_bytes(b"CFF2")))
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{
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Some(_) => CidFontType::Type0,
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None => CidFontType::Type2,
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};
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// Write the base font object referencing the CID font.
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self.writer
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.type0_font(refs.type0_font)
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.base_font(base_font)
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.encoding_predefined(Name(b"Identity-H"))
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.descendant_font(refs.cid_font)
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.to_unicode(refs.cmap);
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// Write the CID font referencing the font descriptor.
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self.writer
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.cid_font(refs.cid_font, subtype)
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.base_font(base_font)
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.system_info(system_info)
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.font_descriptor(refs.font_descriptor)
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.cid_to_gid_map_predefined(Name(b"Identity"))
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.widths()
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.individual(0, {
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let num_glyphs = ttf.number_of_glyphs();
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(0 .. num_glyphs).map(|g| {
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let x = ttf.glyph_hor_advance(GlyphId(g)).unwrap_or(0);
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face.to_em(x).to_pdf()
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})
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});
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// Write the font descriptor (contains metrics about the font).
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self.writer
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.font_descriptor(refs.font_descriptor)
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.font_name(base_font)
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.font_flags(flags)
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.font_bbox(bbox)
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.italic_angle(italic_angle)
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.ascent(ascender)
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.descent(descender)
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.cap_height(cap_height)
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.stem_v(stem_v)
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.font_file2(refs.data);
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// Write the to-unicode character map, which maps glyph ids back to
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// unicode codepoints to enable copying out of the PDF.
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self.writer.cmap(refs.cmap, &{
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// Deduplicate glyph-to-unicode mappings with a set.
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let mut mapping = BTreeMap::new();
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for subtable in ttf.character_mapping_subtables() {
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if subtable.is_unicode() {
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subtable.codepoints(|n| {
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if let Some(c) = std::char::from_u32(n) {
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if let Some(GlyphId(g)) = ttf.glyph_index(c) {
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if glyphs.contains(&g) {
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mapping.insert(g, c);
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}
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}
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}
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});
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}
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}
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let mut cmap = UnicodeCmap::new(cmap_name, system_info);
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for (g, c) in mapping {
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cmap.pair(g, c);
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}
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cmap.finish()
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});
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// Subset and write the face's bytes.
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let original = face.buffer();
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let subsetted = subset(original, face.index(), glyphs.iter().copied());
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let data = subsetted.as_deref().unwrap_or(original);
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self.writer.stream(refs.data, data);
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}
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}
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fn write_images(&mut self) {
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let mut masks_seen = 0;
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for (id, image_id) in self.refs.images().zip(self.image_map.layout_indices()) {
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let img = self.images.get(image_id);
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let (width, height) = img.buf.dimensions();
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// Add the primary image.
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if let Ok((data, filter, color_space)) = encode_image(img) {
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let mut image = self.writer.image(id, &data);
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image.filter(filter);
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image.width(width as i32);
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image.height(height as i32);
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image.color_space(color_space);
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image.bits_per_component(8);
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// Add a second gray-scale image containing the alpha values if
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// this image has an alpha channel.
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if img.buf.color().has_alpha() {
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let (alpha_data, alpha_filter) = encode_alpha(img);
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let mask_id = self.refs.alpha_mask(masks_seen);
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image.s_mask(mask_id);
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drop(image);
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let mut mask = self.writer.image(mask_id, &alpha_data);
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mask.filter(alpha_filter);
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mask.width(width as i32);
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mask.height(height as i32);
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mask.color_space(ColorSpace::DeviceGray);
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mask.bits_per_component(8);
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masks_seen += 1;
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}
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} else {
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// TODO: Warn that image could not be encoded.
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self.writer
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.image(id, &[])
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.width(0)
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.height(0)
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.color_space(ColorSpace::DeviceGray)
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.bits_per_component(1);
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}
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}
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}
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}
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/// Write a fill change into a content stream.
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fn write_fill(content: &mut Content, fill: Paint) {
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let Paint::Color(Color::Rgba(c)) = fill;
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content.fill_rgb(c.r as f32 / 255.0, c.g as f32 / 255.0, c.b as f32 / 255.0);
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}
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/// Write a stroke change into a content stream.
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fn write_stroke(content: &mut Content, stroke: Paint, thickness: f32) {
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match stroke {
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Paint::Color(Color::Rgba(c)) => {
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content.stroke_rgb(
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c.r as f32 / 255.0,
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c.g as f32 / 255.0,
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c.b as f32 / 255.0,
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);
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}
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}
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content.line_width(thickness);
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}
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/// Write a path into a content stream.
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fn write_path(
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content: &mut Content,
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x: f32,
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y: f32,
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path: &geom::Path,
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stroke: bool,
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fill: bool,
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) {
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let f = |length: Length| length.to_pt() as f32;
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let mut builder = content.path(stroke, fill);
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for elem in &path.0 {
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match elem {
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geom::PathElement::MoveTo(p) => builder.move_to(x + f(p.x), y + f(p.y)),
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geom::PathElement::LineTo(p) => builder.line_to(x + f(p.x), y + f(p.y)),
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geom::PathElement::CubicTo(p1, p2, p3) => builder.cubic_to(
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x + f(p1.x),
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y + f(p1.y),
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x + f(p2.x),
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y + f(p2.y),
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x + f(p3.x),
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y + f(p3.y),
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),
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geom::PathElement::ClosePath => builder.close_path(),
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};
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}
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}
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/// The compression level for the deflating.
|
|
const DEFLATE_LEVEL: u8 = 6;
|
|
|
|
/// Encode an image with a suitable filter.
|
|
///
|
|
/// Skips the alpha channel as that's encoded separately.
|
|
fn encode_image(img: &Image) -> ImageResult<(Vec<u8>, Filter, ColorSpace)> {
|
|
let mut data = vec![];
|
|
let (filter, space) = match (img.format, &img.buf) {
|
|
// 8-bit gray JPEG.
|
|
(ImageFormat::Jpeg, DynamicImage::ImageLuma8(_)) => {
|
|
img.buf.write_to(&mut data, img.format)?;
|
|
(Filter::DctDecode, ColorSpace::DeviceGray)
|
|
}
|
|
|
|
// 8-bit Rgb JPEG (Cmyk JPEGs get converted to Rgb earlier).
|
|
(ImageFormat::Jpeg, DynamicImage::ImageRgb8(_)) => {
|
|
img.buf.write_to(&mut data, img.format)?;
|
|
(Filter::DctDecode, ColorSpace::DeviceRgb)
|
|
}
|
|
|
|
// TODO: Encode flate streams with PNG-predictor?
|
|
|
|
// 8-bit gray PNG.
|
|
(ImageFormat::Png, DynamicImage::ImageLuma8(luma)) => {
|
|
data = deflate::compress_to_vec_zlib(&luma.as_raw(), DEFLATE_LEVEL);
|
|
(Filter::FlateDecode, ColorSpace::DeviceGray)
|
|
}
|
|
|
|
// 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);
|
|
}
|
|
|
|
data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
|
|
(Filter::FlateDecode, ColorSpace::DeviceRgb)
|
|
}
|
|
};
|
|
Ok((data, filter, space))
|
|
}
|
|
|
|
/// Encode an image's alpha channel if present.
|
|
fn encode_alpha(img: &Image) -> (Vec<u8>, Filter) {
|
|
let pixels: Vec<_> = img.buf.pixels().map(|(_, _, Rgba([_, _, _, a]))| a).collect();
|
|
let data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
|
|
(data, Filter::FlateDecode)
|
|
}
|
|
|
|
/// We need to know exactly which indirect reference id will be used for which
|
|
/// objects up-front to correctly declare the document catalogue, page tree and
|
|
/// so on. These offsets are computed in the beginning and stored here.
|
|
struct Refs {
|
|
catalog: Ref,
|
|
page_tree: Ref,
|
|
pages_start: i32,
|
|
contents_start: i32,
|
|
fonts_start: i32,
|
|
images_start: i32,
|
|
alpha_masks_start: i32,
|
|
end: i32,
|
|
}
|
|
|
|
struct FontRefs {
|
|
type0_font: Ref,
|
|
cid_font: Ref,
|
|
font_descriptor: Ref,
|
|
cmap: Ref,
|
|
data: Ref,
|
|
}
|
|
|
|
impl Refs {
|
|
const OBJECTS_PER_FONT: usize = 5;
|
|
|
|
fn new(pages: usize, fonts: usize, images: usize, alpha_masks: usize) -> Self {
|
|
let catalog = 1;
|
|
let page_tree = catalog + 1;
|
|
let pages_start = page_tree + 1;
|
|
let contents_start = pages_start + pages as i32;
|
|
let fonts_start = contents_start + pages as i32;
|
|
let images_start = fonts_start + (Self::OBJECTS_PER_FONT * fonts) as i32;
|
|
let alpha_masks_start = images_start + images as i32;
|
|
let end = alpha_masks_start + alpha_masks as i32;
|
|
|
|
Self {
|
|
catalog: Ref::new(catalog),
|
|
page_tree: Ref::new(page_tree),
|
|
pages_start,
|
|
contents_start,
|
|
fonts_start,
|
|
images_start,
|
|
alpha_masks_start,
|
|
end,
|
|
}
|
|
}
|
|
|
|
fn pages(&self) -> impl Iterator<Item = Ref> {
|
|
(self.pages_start .. self.contents_start).map(Ref::new)
|
|
}
|
|
|
|
fn contents(&self) -> impl Iterator<Item = Ref> {
|
|
(self.contents_start .. self.images_start).map(Ref::new)
|
|
}
|
|
|
|
fn fonts(&self) -> impl Iterator<Item = FontRefs> {
|
|
(self.fonts_start .. self.images_start)
|
|
.step_by(Self::OBJECTS_PER_FONT)
|
|
.map(|id| FontRefs {
|
|
type0_font: Ref::new(id),
|
|
cid_font: Ref::new(id + 1),
|
|
font_descriptor: Ref::new(id + 2),
|
|
cmap: Ref::new(id + 3),
|
|
data: Ref::new(id + 4),
|
|
})
|
|
}
|
|
|
|
fn images(&self) -> impl Iterator<Item = Ref> {
|
|
(self.images_start .. self.end).map(Ref::new)
|
|
}
|
|
|
|
fn alpha_mask(&self, i: usize) -> Ref {
|
|
Ref::new(self.alpha_masks_start + i as i32)
|
|
}
|
|
}
|
|
|
|
/// Used to assign new, consecutive PDF-internal indices to things.
|
|
struct Remapper<Index> {
|
|
/// Forwards from the old indices to the new pdf indices.
|
|
to_pdf: HashMap<Index, usize>,
|
|
/// Backwards from the pdf indices to the old indices.
|
|
to_layout: Vec<Index>,
|
|
}
|
|
|
|
impl<Index> Remapper<Index>
|
|
where
|
|
Index: Copy + Eq + Hash,
|
|
{
|
|
fn new() -> Self {
|
|
Self {
|
|
to_pdf: HashMap::new(),
|
|
to_layout: vec![],
|
|
}
|
|
}
|
|
|
|
fn len(&self) -> usize {
|
|
self.to_layout.len()
|
|
}
|
|
|
|
fn insert(&mut self, index: Index) {
|
|
let to_layout = &mut self.to_layout;
|
|
self.to_pdf.entry(index).or_insert_with(|| {
|
|
let pdf_index = to_layout.len();
|
|
to_layout.push(index);
|
|
pdf_index
|
|
});
|
|
}
|
|
|
|
fn map(&self, index: Index) -> usize {
|
|
self.to_pdf[&index]
|
|
}
|
|
|
|
fn pdf_indices(&self) -> impl Iterator<Item = usize> {
|
|
0 .. self.to_pdf.len()
|
|
}
|
|
|
|
fn layout_indices(&self) -> impl Iterator<Item = Index> + '_ {
|
|
self.to_layout.iter().copied()
|
|
}
|
|
}
|
|
|
|
/// Additional methods for [`Em`].
|
|
trait EmExt {
|
|
/// Convert an em length to a number of PDF font units.
|
|
fn to_pdf(self) -> f32;
|
|
}
|
|
|
|
impl EmExt for Em {
|
|
fn to_pdf(self) -> f32 {
|
|
1000.0 * self.get() as f32
|
|
}
|
|
}
|