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LibPDF: Initial support for drawing CFF-based Type0 fonts

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Together with the already-merged #23122, #23128, #23135, #23136, #23162,
and #23167, #23179, #23190, #23194 this adds initial support for
rendering some CFF-based Type0 fonts :^)

There's a long list of things that still need improving after this:

* A small number of CFF programs contain the charstring command 0,
  which is invalid. Currently, this makes us reject the whole font.

* Type1FontProgram::rasterize_glyph() is name-based. For CID-based
  fonts, we want a version that takes CIDs (character IDs) instead.
  For now, I'm printing the CID to a string and using that, yuck.
  (I looked into doing this nicely. I do want to do that, but I
  need to read up on how the `seac` type1 charstring command uses
  character names to identify parts of an accented character.
  Also, it looks like `seac`'s accented character handling moved
  over to `endchar` in type2 charstring commands (i.e. in CFF data),
  and it looks like we don't implement that at all. So I need to do
  more reading first, and I didn't want to block this on that.)

* The name for the first string in name-based CFF fonts looks wrong;
  added a FIXME for that for now.

* This supports the named Identity-H cmap only for now. Identity-H
  maps UTF16-BE values to glyph IDs with the idenity function, and
  assumes it's horizontal text. Other named cmaps in my test files are
  UniJIS-UCS2-H, UniCNS-UCS2-H, Identity-V, UniGB-UCS2-H, UniKS-UCS2-H.
  (There are also 2 files using the stream-based cmaps instead of the
  name-based ones.)

  * In particular, we can't draw vertical text (`-V`) yet

* Passing in the encoding to CFF::create() is awkward (it's nullptr
  for CID-keyed fonts), and it's also not necessary since
  `Type1Font::draw_glyph()` already does the "take encoding from PDF,
  and only from font if the PDF doesn't store one" dance.

* This doesn't cache glyphs but re-rasterizes them each time. Easy
  to add, but maybe I want to look at rotation first. And things
  don't feel glacial as-is.

* Type0Font::draw_glyph() is pretty similar to second half of
  Type1Font::draw_glyph()
This commit is contained in:
Nico Weber 2024-02-15 07:54:08 -05:00 • committed by Tim Flynn
parent c9d48bbca4
commit bd74447dba
2 changed files with 50 additions and 7 deletions
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19
Userland/Libraries/LibPDF/Fonts/CFF.cpp
View file

@ -246,11 +246,24 @@ PDFErrorOr<NonnullRefPtr<CFF>> CFF::create(ReadonlyBytes const& cff_bytes, RefPt
for (size_t i = 0; i < glyphs.size(); i++) {
if (i == 0) {
TRY(cff->add_glyph(0, move(glyphs[0])));
if (top_dict.is_cid_keyed) {
// FIXME: Do better than printing the cid to a string.
auto cid = 0;
TRY(cff->add_glyph(ByteString::formatted("{}", cid), move(glyphs[0])));
} else {
// FIXME: Shouldn't this use resolve_sid(0, strings) (".notdef") as name?
TRY(cff->add_glyph(0, move(glyphs[0])));
}
continue;
}
auto const& name = charset_names[i - 1];
TRY(cff->add_glyph(name, move(glyphs[i])));
if (top_dict.is_cid_keyed) {
// FIXME: Do better than printing the cid to a string.
auto cid = charset[i - 1];
TRY(cff->add_glyph(ByteString::formatted("{}", cid), move(glyphs[i])));
} else {
auto const& name = charset_names[i - 1];
TRY(cff->add_glyph(name, move(glyphs[i])));
}
}
cff->consolidate_glyphs();

38
Userland/Libraries/LibPDF/Fonts/Type0Font.cpp
View file

@ -47,8 +47,8 @@ PDFErrorOr<NonnullOwnPtr<CIDFontType0>> CIDFontType0::create(Document* document,
if (font_file_dict->contains(CommonNames::Subtype))
subtype = font_file_dict->get_name(CommonNames::Subtype)->name();
if (subtype == CommonNames::CIDFontType0C) {
// FIXME: Call CFF::create() and assign the result to font_program once CFF::create() can handle CID-keyed fonts.
return Error::rendering_unsupported_error("Type0 font CIDFontType0: support for CIDFontType0C not yet implemented");
// FIXME: Stop passing an external encoding to CFF::create().
font_program = TRY(CFF::create(font_file_stream->bytes(), /*encoding=*/nullptr));
} else {
// FIXME: Add support for /OpenType.
dbgln("CIDFontType0: unsupported FontFile3 subtype '{}'", subtype);
@ -64,7 +64,7 @@ PDFErrorOr<NonnullOwnPtr<CIDFontType0>> CIDFontType0::create(Document* document,
return TRY(adopt_nonnull_own_or_enomem(new (nothrow) CIDFontType0(move(font_program))));
}
PDFErrorOr<void> CIDFontType0::draw_glyph(Gfx::Painter&, Gfx::FloatPoint, float, u32, Renderer const&)
PDFErrorOr<void> CIDFontType0::draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint point, float width, u32 cid, Renderer const& renderer)
{
// ISO 32000 (PDF 2.0) 9.7.4.2 Glyph selection in CIDFonts
// "When the CIDFont contains an embedded font program that is represented in the Compact Font Format (CFF),
@ -75,7 +75,37 @@ PDFErrorOr<void> CIDFontType0::draw_glyph(Gfx::Painter&, Gfx::FloatPoint, float,
// The GID value shall then be used to look up the glyph procedure using the CharStrings INDEX table [...]
// * The "CFF" font program has a Top DICT that does not use CIDFont operators: The CIDs shall be used
// directly as GID values, and the glyph procedure shall be retrieved using the CharStrings INDEX"
return Error::rendering_unsupported_error("Type0 font CIDFontType0 not implemented yet");
// FIXME: We currently only do the first.
// FIXME: Do better than printing the cid to a string.
auto char_name = ByteString::formatted("{}", cid);
auto translation = m_font_program->glyph_translation(char_name, width);
point = point.translated(translation);
auto glyph_position = Gfx::GlyphRasterPosition::get_nearest_fit_for(point);
// FIXME: Cache the font bitmap (but probably want to figure out rotation first).
auto bitmap = m_font_program->rasterize_glyph(char_name, width, glyph_position.subpixel_offset);
if (!bitmap)
return Error::rendering_unsupported_error("Type0 font CIDFontType0: failed to rasterize glyph");
auto style = renderer.state().paint_style;
if (style.has<Color>()) {
painter.blit_filtered(glyph_position.blit_position, *bitmap, bitmap->rect(), [style](Color pixel) -> Color {
return pixel.multiply(style.get<Color>());
});
} else {
style.get<NonnullRefPtr<Gfx::PaintStyle>>()->paint(bitmap->physical_rect(), [&](auto sample) {
painter.blit_filtered(glyph_position.blit_position, *bitmap, bitmap->rect(), [&](Color pixel) -> Color {
// FIXME: Presumably we need to sample at every point in the glyph, not just the top left?
return pixel.multiply(sample(glyph_position.blit_position));
});
});
}
return {};
}
class CIDFontType2 : public CIDFontType {