mirror of
https://github.com/storytold/pdfcraft.git
synced 2026-11-03 06:51:50 -06:00
refactor(fonts): drop the unused TrueType subsetter
subset_truetype, subset_tag and their table helpers had no caller apart from their own test, and validate_document_input validated twice: names() already runs validate() first. No behaviour change. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
FredApps
co-authored by
Claude Opus 5.5
Claude Opus 5.5
parent
25916985ca
commit
4416405232
@@ -1,7 +1,7 @@
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//! Unicode embedding of an explicitly supplied, embeddable TrueType face. Font files are
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//! document inputs or the optional craft-fonts build input, never system-interface fallbacks.
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use std::collections::{BTreeSet, HashMap};
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use std::collections::HashMap;
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use std::fmt::Write as _;
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use pdfcraft_cos::{Dict, Document, ObjRef, Object, PdfString, Stream};
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@@ -66,7 +66,6 @@ pub fn validate_document_input(bytes: &[u8]) -> Result<(), String> {
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{
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return Err("select an openly licensed font whose name table declares its licence (OFL, Apache, Ubuntu, Bitstream Vera or MIT)".into());
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}
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validate(bytes)?;
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Ok(())
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}
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@@ -338,448 +337,6 @@ fn same_resource(doc: &Document, fonts: &Dict, name: &str, programs: &mut Progra
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.map(|w| w.resource)
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}
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/// Generate a 6-character subset prefix tag for a font name, e.g. "ABCDEF+".
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pub fn subset_tag(seed: u64) -> String {
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let mut tag = String::with_capacity(7);
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let mut s = seed;
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for _ in 0..6 {
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let b = b'A'.saturating_add((s % 26) as u8);
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tag.push(b as char);
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s /= 26;
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}
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tag.push('+');
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tag
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}
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fn calc_table_checksum(data: &[u8]) -> u32 {
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let mut sum = 0u32;
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for chunk in data.chunks(4) {
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let mut b = [0u8; 4];
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if let Some(target) = b.get_mut(..chunk.len()) {
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target.copy_from_slice(chunk);
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}
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sum = sum.wrapping_add(u32::from_be_bytes(b));
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}
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sum
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}
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fn read_tables(bytes: &[u8]) -> Option<HashMap<[u8; 4], &[u8]>> {
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let count_bytes: [u8; 2] = bytes.get(4..6)?.try_into().ok()?;
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let num_tables = usize::from(u16::from_be_bytes(count_bytes));
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if num_tables > 128 {
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return None;
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}
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let mut map = HashMap::new();
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for i in 0..num_tables {
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let entry = 12usize.checked_add(i.checked_mul(16)?)?;
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let tag: [u8; 4] = bytes.get(entry..entry.checked_add(4)?)?.try_into().ok()?;
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let off_bytes: [u8; 4] = bytes.get(entry.checked_add(8)?..entry.checked_add(12)?)?.try_into().ok()?;
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let offset = usize::try_from(u32::from_be_bytes(off_bytes)).ok()?;
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let len_bytes: [u8; 4] = bytes.get(entry.checked_add(12)?..entry.checked_add(16)?)?.try_into().ok()?;
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let length = usize::try_from(u32::from_be_bytes(len_bytes)).ok()?;
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let table_data = bytes.get(offset..offset.checked_add(length)?)?;
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map.insert(tag, table_data);
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}
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Some(map)
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}
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fn glyph_slice<'a>(loca: &'a [u8], glyf: &'a [u8], is_long: bool, gid: u16) -> Option<&'a [u8]> {
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let (start, end) = if is_long {
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let s_idx = usize::from(gid).checked_mul(4)?;
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let e_idx = s_idx.checked_add(4)?;
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let start_bytes: [u8; 4] = loca.get(s_idx..e_idx)?.try_into().ok()?;
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let end_bytes: [u8; 4] = loca.get(e_idx..e_idx.checked_add(4)?)?.try_into().ok()?;
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(usize::try_from(u32::from_be_bytes(start_bytes)).ok()?, usize::try_from(u32::from_be_bytes(end_bytes)).ok()?)
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} else {
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let s_idx = usize::from(gid).checked_mul(2)?;
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let e_idx = s_idx.checked_add(2)?;
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let start_bytes: [u8; 2] = loca.get(s_idx..e_idx)?.try_into().ok()?;
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let end_bytes: [u8; 2] = loca.get(e_idx..e_idx.checked_add(2)?)?.try_into().ok()?;
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(usize::from(u16::from_be_bytes(start_bytes)).checked_mul(2)?, usize::from(u16::from_be_bytes(end_bytes)).checked_mul(2)?)
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};
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if start <= end && end <= glyf.len() { glyf.get(start..end) } else { None }
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}
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fn composite_components(data: &[u8]) -> Vec<u16> {
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let mut comps = Vec::new();
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if data.len() < 10 {
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return comps;
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}
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let Some(header) = data.get(0..2) else { return comps };
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let num_contours = i16::from_be_bytes([header[0], header[1]]);
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if num_contours != -1 {
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return comps;
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}
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let mut offset = 10usize;
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while let Some(flags_bytes) = data.get(offset..offset.saturating_add(2)) {
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if flags_bytes.len() < 2 {
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break;
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}
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let flags = u16::from_be_bytes([flags_bytes[0], flags_bytes[1]]);
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let Some(gid_bytes) = data.get(offset.saturating_add(2)..offset.saturating_add(4)) else { break };
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if gid_bytes.len() < 2 {
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break;
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}
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let gid = u16::from_be_bytes([gid_bytes[0], gid_bytes[1]]);
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comps.push(gid);
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let Some(mut next_offset) = offset.checked_add(4) else { break };
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if flags & 0x0001 != 0 {
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next_offset = match next_offset.checked_add(4) {
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Some(o) => o,
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None => break,
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};
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} else {
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next_offset = match next_offset.checked_add(2) {
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Some(o) => o,
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None => break,
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};
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}
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if flags & 0x0008 != 0 {
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next_offset = match next_offset.checked_add(2) {
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Some(o) => o,
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None => break,
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};
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} else if flags & 0x0040 != 0 {
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next_offset = match next_offset.checked_add(4) {
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Some(o) => o,
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None => break,
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};
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} else if flags & 0x0080 != 0 {
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next_offset = match next_offset.checked_add(8) {
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Some(o) => o,
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None => break,
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};
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}
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offset = next_offset;
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if flags & 0x0020 == 0 {
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break;
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}
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}
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comps
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}
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fn remap_composite_glyph(data: &[u8], old_to_new: &HashMap<u16, u16>) -> Vec<u8> {
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let mut out = data.to_vec();
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if out.len() < 10 {
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return out;
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}
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let Some(header) = out.get(0..2) else { return out };
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let num_contours = i16::from_be_bytes([header[0], header[1]]);
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if num_contours != -1 {
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return out;
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}
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let mut offset = 10usize;
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while let Some(flags_bytes) = out.get(offset..offset.saturating_add(2)) {
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if flags_bytes.len() < 2 {
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break;
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}
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let flags = u16::from_be_bytes([flags_bytes[0], flags_bytes[1]]);
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let Some(gid_bytes) = out.get(offset.saturating_add(2)..offset.saturating_add(4)) else { break };
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if gid_bytes.len() < 2 {
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break;
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}
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let old_gid = u16::from_be_bytes([gid_bytes[0], gid_bytes[1]]);
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let new_gid = old_to_new.get(&old_gid).copied().unwrap_or(0);
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if let Some(slot) = out.get_mut(offset.saturating_add(2)..offset.saturating_add(4)) {
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slot.copy_from_slice(&new_gid.to_be_bytes());
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}
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let Some(mut next_offset) = offset.checked_add(4) else { break };
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if flags & 0x0001 != 0 {
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next_offset = match next_offset.checked_add(4) {
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Some(o) => o,
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None => break,
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};
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} else {
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next_offset = match next_offset.checked_add(2) {
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Some(o) => o,
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None => break,
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};
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}
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if flags & 0x0008 != 0 {
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next_offset = match next_offset.checked_add(2) {
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Some(o) => o,
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None => break,
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};
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} else if flags & 0x0040 != 0 {
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next_offset = match next_offset.checked_add(4) {
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Some(o) => o,
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None => break,
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};
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} else if flags & 0x0080 != 0 {
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next_offset = match next_offset.checked_add(8) {
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Some(o) => o,
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None => break,
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};
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}
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offset = next_offset;
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if flags & 0x0020 == 0 {
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break;
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}
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}
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out
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}
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fn build_name_table(ps_name: &str) -> Vec<u8> {
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let utf16_be: Vec<u8> = ps_name.encode_utf16().flat_map(u16::to_be_bytes).collect();
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let str_len = u16::try_from(utf16_be.len()).unwrap_or(0);
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let mut out = Vec::new();
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out.extend_from_slice(&0u16.to_be_bytes());
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out.extend_from_slice(&1u16.to_be_bytes());
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out.extend_from_slice(&18u16.to_be_bytes());
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out.extend_from_slice(&3u16.to_be_bytes());
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out.extend_from_slice(&1u16.to_be_bytes());
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out.extend_from_slice(&0x0409u16.to_be_bytes());
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out.extend_from_slice(&6u16.to_be_bytes());
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out.extend_from_slice(&str_len.to_be_bytes());
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out.extend_from_slice(&0u16.to_be_bytes());
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out.extend_from_slice(&utf16_be);
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out
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}
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fn build_cmap_table(char_to_new_gid: &[(u32, u32)]) -> Vec<u8> {
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let mut sorted = char_to_new_gid.to_vec();
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if sorted.is_empty() {
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sorted.push((0, 0));
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}
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sorted.sort_by_key(|&(c, _)| c);
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sorted.dedup_by_key(|&mut (c, _)| c);
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let n_groups = u32::try_from(sorted.len()).unwrap_or(1);
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let subtable_len = 16u32.saturating_add(n_groups.saturating_mul(12));
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let mut out = Vec::new();
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out.extend_from_slice(&0u16.to_be_bytes());
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out.extend_from_slice(&1u16.to_be_bytes());
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out.extend_from_slice(&3u16.to_be_bytes());
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out.extend_from_slice(&10u16.to_be_bytes());
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out.extend_from_slice(&12u32.to_be_bytes());
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out.extend_from_slice(&12u16.to_be_bytes());
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out.extend_from_slice(&0u16.to_be_bytes());
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out.extend_from_slice(&subtable_len.to_be_bytes());
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out.extend_from_slice(&0u32.to_be_bytes());
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out.extend_from_slice(&n_groups.to_be_bytes());
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for &(c, gid) in &sorted {
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out.extend_from_slice(&c.to_be_bytes());
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out.extend_from_slice(&c.to_be_bytes());
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out.extend_from_slice(&gid.to_be_bytes());
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}
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out
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}
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/// Subset a TrueType font to only the specified glyph IDs.
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/// Returns the new sfnt font binary and a mapping from old GID to new GID.
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#[allow(clippy::cognitive_complexity)]
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pub fn subset_truetype(bytes: &[u8], used_gids: &[u16], postscript_name: &str) -> Result<(Vec<u8>, HashMap<u16, u16>), String> {
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validate(bytes)?;
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let map = read_tables(bytes).ok_or("cannot parse font table directory")?;
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let orig_glyf = map.get(b"glyf").copied().ok_or("the font has no TrueType glyf table")?;
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let orig_loca = map.get(b"loca").copied().ok_or("missing loca table")?;
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let orig_head = map.get(b"head").copied().ok_or("missing head table")?;
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let orig_hhea = map.get(b"hhea").copied().ok_or("missing hhea table")?;
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let orig_hmtx = map.get(b"hmtx").copied().ok_or("missing hmtx table")?;
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let orig_maxp = map.get(b"maxp").copied().ok_or("missing maxp table")?;
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let index_fmt_bytes: [u8; 2] = orig_head.get(50..52).ok_or("invalid head table")?.try_into().map_err(|_| "invalid head table")?;
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let is_long = i16::from_be_bytes(index_fmt_bytes) != 0;
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let mut needed_gids = BTreeSet::new();
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needed_gids.insert(0u16);
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for &g in used_gids {
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needed_gids.insert(g);
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}
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let mut queue: Vec<u16> = needed_gids.iter().copied().collect();
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while let Some(gid) = queue.pop() {
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if let Some(g_data) = glyph_slice(orig_loca, orig_glyf, is_long, gid) {
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for comp in composite_components(g_data) {
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if needed_gids.insert(comp) {
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queue.push(comp);
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}
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}
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}
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}
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let mut subset_glyphs = Vec::with_capacity(needed_gids.len());
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let mut old_to_new_gid = HashMap::new();
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for (new_gid, &old_gid) in needed_gids.iter().enumerate() {
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let new_gid_u16 = u16::try_from(new_gid).map_err(|_| "too many glyphs in subset")?;
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old_to_new_gid.insert(old_gid, new_gid_u16);
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subset_glyphs.push(old_gid);
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}
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let mut subset_glyf = Vec::new();
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let mut subset_loca = Vec::with_capacity((subset_glyphs.len().saturating_add(1)).saturating_mul(4));
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for &old_gid in &subset_glyphs {
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let offset_u32 = u32::try_from(subset_glyf.len()).map_err(|_| "glyf table overflow")?;
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subset_loca.extend_from_slice(&offset_u32.to_be_bytes());
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if let Some(g_data) = glyph_slice(orig_loca, orig_glyf, is_long, old_gid)
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&& !g_data.is_empty()
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{
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let remapped = remap_composite_glyph(g_data, &old_to_new_gid);
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subset_glyf.extend_from_slice(&remapped);
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if subset_glyf.len() % 2 != 0 {
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subset_glyf.push(0);
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}
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}
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}
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let final_offset_u32 = u32::try_from(subset_glyf.len()).map_err(|_| "glyf table overflow")?;
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subset_loca.extend_from_slice(&final_offset_u32.to_be_bytes());
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let hmetrics_bytes: [u8; 2] = orig_hhea.get(34..36).ok_or("invalid hhea")?.try_into().map_err(|_| "invalid hhea")?;
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let orig_num_hmetrics = usize::from(u16::from_be_bytes(hmetrics_bytes));
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let mut subset_hmtx = Vec::with_capacity(subset_glyphs.len().saturating_mul(4));
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for &old_gid in &subset_glyphs {
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let old_idx = usize::from(old_gid);
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let (adv, lsb) = if old_idx < orig_num_hmetrics {
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let adv_bytes: [u8; 2] = orig_hmtx.get(old_idx * 4..old_idx * 4 + 2).unwrap_or(&[0, 0]).try_into().unwrap_or([0, 0]);
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let lsb_bytes: [u8; 2] = orig_hmtx.get(old_idx * 4 + 2..old_idx * 4 + 4).unwrap_or(&[0, 0]).try_into().unwrap_or([0, 0]);
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(u16::from_be_bytes(adv_bytes), i16::from_be_bytes(lsb_bytes))
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} else {
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let last_adv_offset = orig_num_hmetrics.saturating_sub(1) * 4;
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let adv_bytes: [u8; 2] = orig_hmtx.get(last_adv_offset..last_adv_offset + 2).unwrap_or(&[0, 0]).try_into().unwrap_or([0, 0]);
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let lsb_offset = orig_num_hmetrics * 4 + (old_idx.saturating_sub(orig_num_hmetrics)) * 2;
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let lsb_bytes: [u8; 2] = orig_hmtx.get(lsb_offset..lsb_offset + 2).unwrap_or(&[0, 0]).try_into().unwrap_or([0, 0]);
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(u16::from_be_bytes(adv_bytes), i16::from_be_bytes(lsb_bytes))
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};
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subset_hmtx.extend_from_slice(&adv.to_be_bytes());
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subset_hmtx.extend_from_slice(&lsb.to_be_bytes());
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}
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let mut subset_hhea = orig_hhea.to_vec();
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if subset_hhea.len() >= 36 {
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let num_metrics = u16::try_from(subset_glyphs.len()).map_err(|_| "too many glyphs")?;
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if let Some(target) = subset_hhea.get_mut(34..36) {
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target.copy_from_slice(&num_metrics.to_be_bytes());
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}
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}
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let mut subset_maxp = orig_maxp.to_vec();
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if subset_maxp.len() >= 6 {
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let num_g = u16::try_from(subset_glyphs.len()).map_err(|_| "too many glyphs")?;
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if let Some(target) = subset_maxp.get_mut(4..6) {
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target.copy_from_slice(&num_g.to_be_bytes());
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}
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}
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let mut subset_head = orig_head.to_vec();
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if subset_head.len() >= 54 {
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if let Some(target) = subset_head.get_mut(8..12) {
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target.copy_from_slice(&[0, 0, 0, 0]);
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}
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if let Some(target) = subset_head.get_mut(50..52) {
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target.copy_from_slice(&1i16.to_be_bytes());
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}
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}
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let mut subset_post = vec![0u8; 32];
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if let Some(target) = subset_post.get_mut(0..4) {
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target.copy_from_slice(&0x00030000u32.to_be_bytes());
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}
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if let Some(orig_post) = map.get(b"post")
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&& orig_post.len() >= 16
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&& let (Some(target), Some(src)) = (subset_post.get_mut(4..16), orig_post.get(4..16))
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{
|
||||
target.copy_from_slice(src);
|
||||
}
|
||||
|
||||
let char_to_new: Vec<(u32, u32)> = FontRef::new(bytes)
|
||||
.ok()
|
||||
.map(|face| {
|
||||
face.charmap().mappings().filter_map(|(cp, old)| old_to_new_gid.get(&(old.to_u32() as u16)).map(|&new| (cp, u32::from(new)))).collect()
|
||||
})
|
||||
.unwrap_or_default();
|
||||
|
||||
let subset_name = build_name_table(postscript_name);
|
||||
let subset_cmap = build_cmap_table(&char_to_new);
|
||||
|
||||
let mut tables: Vec<([u8; 4], Vec<u8>)> = vec![
|
||||
(*b"cmap", subset_cmap),
|
||||
(*b"glyf", subset_glyf),
|
||||
(*b"head", subset_head),
|
||||
(*b"hhea", subset_hhea),
|
||||
(*b"hmtx", subset_hmtx),
|
||||
(*b"loca", subset_loca),
|
||||
(*b"maxp", subset_maxp),
|
||||
(*b"name", subset_name),
|
||||
];
|
||||
if let Some(os2) = map.get(b"OS/2") {
|
||||
tables.push((*b"OS/2", os2.to_vec()));
|
||||
}
|
||||
if let Some(cvt) = map.get(b"cvt ") {
|
||||
tables.push((*b"cvt ", cvt.to_vec()));
|
||||
}
|
||||
if let Some(fpgm) = map.get(b"fpgm") {
|
||||
tables.push((*b"fpgm", fpgm.to_vec()));
|
||||
}
|
||||
if let Some(prep) = map.get(b"prep") {
|
||||
tables.push((*b"prep", prep.to_vec()));
|
||||
}
|
||||
tables.push((*b"post", subset_post));
|
||||
|
||||
tables.sort_by_key(|t| t.0);
|
||||
|
||||
let num_tables = u16::try_from(tables.len()).map_err(|_| "too many tables")?;
|
||||
let mut max_pow2 = 1u16;
|
||||
let mut entry_selector = 0u16;
|
||||
while max_pow2.saturating_mul(2) <= num_tables {
|
||||
max_pow2 = max_pow2.saturating_mul(2);
|
||||
entry_selector = entry_selector.saturating_add(1);
|
||||
}
|
||||
let search_range = max_pow2.saturating_mul(16);
|
||||
let range_shift = num_tables.saturating_mul(16).saturating_sub(search_range);
|
||||
|
||||
let mut sfnt = Vec::new();
|
||||
sfnt.extend_from_slice(&0x00010000u32.to_be_bytes());
|
||||
sfnt.extend_from_slice(&num_tables.to_be_bytes());
|
||||
sfnt.extend_from_slice(&search_range.to_be_bytes());
|
||||
sfnt.extend_from_slice(&entry_selector.to_be_bytes());
|
||||
sfnt.extend_from_slice(&range_shift.to_be_bytes());
|
||||
|
||||
let dir_size = 12usize.saturating_add(usize::from(num_tables).saturating_mul(16));
|
||||
let mut current_offset = dir_size;
|
||||
|
||||
struct Rec {
|
||||
tag: [u8; 4],
|
||||
checksum: u32,
|
||||
offset: u32,
|
||||
length: u32,
|
||||
}
|
||||
let mut records = Vec::with_capacity(tables.len());
|
||||
for (tag, data) in &tables {
|
||||
let checksum = calc_table_checksum(data);
|
||||
let offset = u32::try_from(current_offset).map_err(|_| "font offset overflow")?;
|
||||
let length = u32::try_from(data.len()).map_err(|_| "font table overflow")?;
|
||||
records.push(Rec { tag: *tag, checksum, offset, length });
|
||||
let padded_len = (data.len().saturating_add(3)) & !3;
|
||||
current_offset = current_offset.saturating_add(padded_len);
|
||||
}
|
||||
|
||||
for r in &records {
|
||||
sfnt.extend_from_slice(&r.tag);
|
||||
sfnt.extend_from_slice(&r.checksum.to_be_bytes());
|
||||
sfnt.extend_from_slice(&r.offset.to_be_bytes());
|
||||
sfnt.extend_from_slice(&r.length.to_be_bytes());
|
||||
}
|
||||
|
||||
let mut head_offset = None;
|
||||
for (r, (_, data)) in records.iter().zip(&tables) {
|
||||
if &r.tag == b"head" {
|
||||
head_offset = Some(sfnt.len());
|
||||
}
|
||||
sfnt.extend_from_slice(data);
|
||||
while sfnt.len() % 4 != 0 {
|
||||
sfnt.push(0);
|
||||
}
|
||||
}
|
||||
|
||||
if let Some(h_off) = head_offset {
|
||||
let file_checksum = calc_table_checksum(&sfnt);
|
||||
let adjustment = 0xB1B0AFBAu32.wrapping_sub(file_checksum);
|
||||
if let Some(slot) = sfnt.get_mut(h_off.saturating_add(8)..h_off.saturating_add(12)) {
|
||||
slot.copy_from_slice(&adjustment.to_be_bytes());
|
||||
}
|
||||
}
|
||||
|
||||
Ok((sfnt, old_to_new_gid))
|
||||
}
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::*;
|
||||
@@ -930,19 +487,4 @@ mod tests {
|
||||
assert_eq!(programs, 1, "one program for both pages");
|
||||
assert!(doc.scan_objects().count() > objects, "the second page gets its own resource");
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn subset_truetype_creates_valid_compact_font() {
|
||||
let bytes = include_bytes!("../../../assets/fonts/Inter-Regular.ttf");
|
||||
let face = FontRef::new(bytes).unwrap();
|
||||
let gid_t = face.charmap().map('T').unwrap().to_u32() as u16;
|
||||
let gid_e = face.charmap().map('e').unwrap().to_u32() as u16;
|
||||
let (subset, mapping) = subset_truetype(bytes, &[gid_t, gid_e], "ABCDEF+Inter-Regular").unwrap();
|
||||
assert!(subset.len() < 10_000, "subset should be tiny, was {}", subset.len());
|
||||
assert!(mapping.contains_key(&gid_t));
|
||||
assert!(mapping.contains_key(&gid_e));
|
||||
let sub_face = FontRef::new(&subset).unwrap();
|
||||
assert_eq!(sub_face.charmap().map('T').unwrap().to_u32(), u32::from(*mapping.get(&gid_t).unwrap()));
|
||||
assert_eq!(sub_face.charmap().map('e').unwrap().to_u32(), u32::from(*mapping.get(&gid_e).unwrap()));
|
||||
}
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user