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https://github.com/typst/typst
synced 2025-05-21 04:25:28 +08:00
Compress all PDF streams
This commit is contained in:
Laurenz
parent
f2882bf854
commit
0471e51bc4
@ -6,7 +6,6 @@ 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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@ -280,7 +279,9 @@ impl<'a> PdfExporter<'a> {
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}
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}
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self.writer.stream(id, &content.finish());
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self.writer
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.stream(id, &deflate(&content.finish()))
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.filter(Filter::FlateDecode);
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}
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fn write_fonts(&mut self) {
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@ -289,10 +290,10 @@ impl<'a> PdfExporter<'a> {
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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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let postcript_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 = format!("ABCDEF+{}", postcript_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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@ -301,8 +302,42 @@ impl<'a> PdfExporter<'a> {
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supplement: 0,
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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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// 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 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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let mut flags = FontFlags::empty();
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flags.set(FontFlags::SERIF, name.contains("Serif"));
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flags.set(FontFlags::SERIF, postcript_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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@ -322,40 +357,6 @@ impl<'a> PdfExporter<'a> {
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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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@ -369,10 +370,8 @@ impl<'a> PdfExporter<'a> {
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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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// Compute a reverse mapping from glyphs to unicode.
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let cmap = {
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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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@ -392,14 +391,22 @@ impl<'a> PdfExporter<'a> {
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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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cmap
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};
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// Write the /ToUnicode 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
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.cmap(refs.cmap, &deflate(&cmap.finish()))
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.filter(Filter::FlateDecode);
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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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let buffer = face.buffer();
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let subsetted = subset(buffer, face.index(), glyphs.iter().copied());
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let data = subsetted.as_deref().unwrap_or(buffer);
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self.writer
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.stream(refs.data, &deflate(data))
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.filter(Filter::FlateDecode);
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}
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}
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@ -504,26 +511,27 @@ const DEFLATE_LEVEL: u8 = 6;
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///
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/// Skips the alpha channel as that's encoded separately.
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fn encode_image(img: &Image) -> ImageResult<(Vec<u8>, Filter, ColorSpace)> {
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let mut data = vec![];
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let (filter, space) = match (img.format, &img.buf) {
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Ok(match (img.format, &img.buf) {
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// 8-bit gray JPEG.
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(ImageFormat::Jpeg, DynamicImage::ImageLuma8(_)) => {
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let mut data = vec![];
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img.buf.write_to(&mut data, img.format)?;
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(Filter::DctDecode, ColorSpace::DeviceGray)
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(data, Filter::DctDecode, ColorSpace::DeviceGray)
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}
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// 8-bit Rgb JPEG (Cmyk JPEGs get converted to Rgb earlier).
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(ImageFormat::Jpeg, DynamicImage::ImageRgb8(_)) => {
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let mut data = vec![];
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img.buf.write_to(&mut data, img.format)?;
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(Filter::DctDecode, ColorSpace::DeviceRgb)
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(data, Filter::DctDecode, ColorSpace::DeviceRgb)
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}
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// TODO: Encode flate streams with PNG-predictor?
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// 8-bit gray PNG.
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(ImageFormat::Png, DynamicImage::ImageLuma8(luma)) => {
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data = deflate::compress_to_vec_zlib(&luma.as_raw(), DEFLATE_LEVEL);
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(Filter::FlateDecode, ColorSpace::DeviceGray)
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let data = deflate(&luma.as_raw());
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(data, Filter::FlateDecode, ColorSpace::DeviceGray)
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}
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// Anything else (including Rgb(a) PNGs).
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@ -536,18 +544,21 @@ fn encode_image(img: &Image) -> ImageResult<(Vec<u8>, Filter, ColorSpace)> {
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pixels.push(b);
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}
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data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
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(Filter::FlateDecode, ColorSpace::DeviceRgb)
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let data = deflate(&pixels);
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(data, Filter::FlateDecode, ColorSpace::DeviceRgb)
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}
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};
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Ok((data, filter, space))
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})
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}
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/// Encode an image's alpha channel if present.
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fn encode_alpha(img: &Image) -> (Vec<u8>, Filter) {
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let pixels: Vec<_> = img.buf.pixels().map(|(_, _, Rgba([_, _, _, a]))| a).collect();
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let data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
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(data, Filter::FlateDecode)
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(deflate(&pixels), Filter::FlateDecode)
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}
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/// Compress data with the DEFLATE algorithm.
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fn deflate(data: &[u8]) -> Vec<u8> {
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miniz_oxide::deflate::compress_to_vec_zlib(data, DEFLATE_LEVEL)
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}
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/// We need to know exactly which indirect reference id will be used for which
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