mirror of
https://github.com/storytold/pdfcraft.git
synced 2026-10-24 10:08:00 -06:00
fix(preflight): read device colour from content operators, not whitespace-split bytes (#2260)
uses_device_colour found content streams by their dictionaries and split their bytes on whitespace. It skipped form XObjects with /Type /XObject and tiling patterns, missed `cs`/`CS` with a device space, inline images and operators before a delimiter, and took a `k` in a string, a comment, inline image data, a font program or an ICC profile for DeviceCMYK. A CMYK logo in a form therefore got an sRGB output intent and passed pdfa_verify. Content streams are now found by role (page /Contents, Type 3 glyphs, forms, appearance streams, tiling patterns) and read with pdfcraft_content::parse. Reading stops once all three device spaces are seen.
This commit is contained in:
Guillem Hermida
Generated
+1
@@ -4195,6 +4195,7 @@ dependencies = [
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name = "pdfcraft-preflight"
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version = "0.8.0"
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dependencies = [
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"pdfcraft-content",
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"pdfcraft-cos",
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"pdfcraft-model",
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]
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@@ -11,5 +11,6 @@ repository.workspace = true
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workspace = true
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[dependencies]
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pdfcraft-content = { workspace = true }
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pdfcraft-cos = { workspace = true }
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pdfcraft-model = { workspace = true }
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+120
-14
@@ -24,7 +24,7 @@
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pub mod icc;
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mod xmp;
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use pdfcraft_cos::{Dict, Document, ObjRef, Object, PdfString, Stream, is_whitespace};
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use pdfcraft_cos::{Dict, Document, ObjRef, Object, PdfString, Stream};
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/// The PDF/A part and conformance level.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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@@ -255,12 +255,124 @@ impl DeviceColour {
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fn any(self) -> bool {
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self.gray || self.rgb || self.cmyk
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}
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/// Note the device colour space `name`, if it is one. Inline images may also use the
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/// abbreviations (`G`, `RGB`, `CMYK`); anywhere else those are resource names.
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fn mark(&mut self, name: &[u8], inline: bool) {
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match name {
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b"DeviceGray" => self.gray = true,
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b"DeviceRGB" => self.rgb = true,
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b"DeviceCMYK" => self.cmyk = true,
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b"G" if inline => self.gray = true,
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b"RGB" if inline => self.rgb = true,
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b"CMYK" if inline => self.cmyk = true,
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_ => {}
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}
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}
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}
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/// How deep [`type3_procs`] looks into an object's direct dictionaries and arrays.
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const MAX_DIRECT_DEPTH: u8 = 8;
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/// The glyph procedures of every Type 3 font in `d`: `d` itself, or a font held directly inside
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/// it (a font can sit inline in a resource dictionary).
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fn type3_procs(doc: &Document, d: &Dict, depth: u8, out: &mut std::collections::HashSet<ObjRef>) {
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if d.name(b"Subtype") == Some(b"Type3")
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&& let Some(procs) = d.get(b"CharProcs").map(|c| doc.resolve(c))
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&& let Some(procs) = procs.as_dict()
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{
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out.extend(procs.iter().filter_map(|(_, p)| p.as_ref()));
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}
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for (_, v) in d.iter() {
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type3_procs_within(doc, v, depth.saturating_add(1), out);
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}
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}
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fn type3_procs_within(doc: &Document, o: &Object, depth: u8, out: &mut std::collections::HashSet<ObjRef>) {
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if depth > MAX_DIRECT_DEPTH {
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return;
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}
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match o {
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Object::Dict(d) => type3_procs(doc, d, depth, out),
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Object::Array(a) => {
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for v in a {
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type3_procs_within(doc, v, depth.saturating_add(1), out);
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}
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}
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_ => {}
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}
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}
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/// The content streams that only a reference identifies, their dictionaries saying nothing: the
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/// pages' `/Contents` and Type 3 glyph procedures.
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fn referenced_content(doc: &Document, objs: &[(ObjRef, std::sync::Arc<Object>)]) -> std::collections::HashSet<ObjRef> {
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let mut out = std::collections::HashSet::new();
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for p in pdfcraft_model::pages(doc) {
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let contents = match p.dict.get(b"Contents") {
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Some(Object::Ref(r)) => match &*doc.get(*r) {
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Object::Array(a) => a.clone(),
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_ => vec![Object::Ref(*r)],
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},
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Some(Object::Array(a)) => a.clone(),
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_ => Vec::new(),
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};
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out.extend(contents.iter().filter_map(Object::as_ref));
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}
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for (_, o) in objs {
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if let Some(d) = dict_of(o) {
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type3_procs(doc, d, 0, &mut out);
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}
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}
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out
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}
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/// Whether a stream's own dictionary says it holds content: a form XObject, or a stream with a
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/// `/BBox` and no `/Subtype` (a tiling pattern, or an appearance stream that leaves out
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/// `/Subtype /Form`). Mesh shadings may carry a `/BBox` too, but their data isn't content.
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fn is_content(d: &Dict) -> bool {
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match d.name(b"Subtype") {
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Some(t) => t == b"Form",
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None => d.get(b"BBox").is_some() && d.get(b"ShadingType").is_none(),
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}
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}
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/// The device colour a content stream sets. It is read operator by operator, so the bytes of a
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/// string, a comment or an inline image are never taken for an operator, and an operator right
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/// before a delimiter (`1 k/GS0 gs`) is still found.
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fn content_colour(data: &[u8], used: &mut DeviceColour) {
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for op in pdfcraft_content::parse(data).ops {
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match op.op.as_slice() {
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b"g" | b"G" => used.gray = true,
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b"rg" | b"RG" => used.rgb = true,
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b"k" | b"K" => used.cmyk = true,
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b"cs" | b"CS" => {
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if let Some(name) = op.name(0) {
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used.mark(name, false);
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}
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}
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b"BI" => {
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let Some((image, _)) = &op.inline else { continue };
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match image.get(b"CS").or_else(|| image.get(b"ColorSpace")) {
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Some(Object::Name(n)) => used.mark(n, true),
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// An indexed space draws in its base: `[/I /DeviceRGB 1 <…>]`.
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Some(Object::Array(a)) if a.first().and_then(Object::as_name).is_some_and(|n| n == b"I" || n == b"Indexed") => {
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if let Some(base) = a.get(1).and_then(Object::as_name) {
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used.mark(base, true);
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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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}
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}
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}
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/// Whether any content or object uses a device colour space.
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fn uses_device_colour(doc: &Document, objs: &[(ObjRef, std::sync::Arc<Object>)]) -> DeviceColour {
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let mut used = DeviceColour::default();
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for (_, o) in objs {
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let referenced = referenced_content(doc, objs);
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for (r, o) in objs {
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let Some(d) = dict_of(o) else { continue };
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// A resource dictionary's /ColorSpace, whether it is this object or the page's inline
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// /Resources.
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@@ -281,20 +393,14 @@ fn uses_device_colour(doc: &Document, objs: &[(ObjRef, std::sync::Arc<Object>)])
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_ => {}
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}
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}
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if let Object::Stream(s) = &**o
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&& d.get(b"Type").is_none()
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&& d.get(b"Subtype").is_none_or(|t| t.as_name() == Some(b"Form"))
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// Content streams only: a font program or an ICC profile is data, whatever bytes it holds.
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// Parsing is the expensive part, so once content has used all three spaces no more is read.
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if !(used.gray && used.rgb && used.cmyk)
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&& let Object::Stream(s) = &**o
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&& (referenced.contains(r) || is_content(&s.dict))
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&& let Ok(data) = s.decoded()
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{
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// Content streams: rg/RG/g/G/k/K operators.
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for token in data.split(|b| is_whitespace(*b)) {
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match token {
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b"g" | b"G" => used.gray = true,
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b"rg" | b"RG" => used.rgb = true,
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b"k" | b"K" => used.cmyk = true,
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_ => {}
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}
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}
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content_colour(&data, &mut used);
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}
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}
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used
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@@ -250,3 +250,124 @@ fn device_colour_is_found_after_any_whitespace() {
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}
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}
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}
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/// A page that draws `content` with `resources`, followed by `extra` objects (from object 5 on).
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fn drawing(content: &str, resources: &str, extra: &[&str]) -> Document {
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let stream = format!("<< /Length {} >>\nstream\n{content}\nendstream", content.len());
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let page = format!("<< /Type /Page /Parent 2 0 R /Contents 4 0 R /Resources << {resources} >> >>");
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let mut objs = vec![
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"<< /Type /Catalog /Pages 2 0 R >>",
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"<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 200 200] >>",
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page.as_str(),
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stream.as_str(),
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];
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objs.extend_from_slice(extra);
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build(&objs, "")
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}
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fn uses_cmyk(doc: &Document) -> bool {
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messages(&verify(doc, Level::A2b)).contains(&"DeviceCMYK is used: it needs a CMYK output intent (not added automatically)")
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}
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/// Issue #2259: a `k` is DeviceCMYK only when it is an operator. Inside a string, a comment, an inline image's
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/// data, a font program, an ICC profile or a mesh shading's data it is just a byte, and the
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/// document still gets its sRGB output intent.
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#[test]
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fn device_colour_is_read_from_operators_not_bytes() {
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let rgb = "1 0 0 rg 0 0 10 10 re f";
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let cases: &[(&str, String, &str, Vec<&str>)] = &[
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(
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"a string",
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format!("{rgb} BT /F1 12 Tf 10 10 Td (press k now) Tj ET"),
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"/Font << /F1 5 0 R >>",
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vec![
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"<< /Type /Font /Subtype /TrueType /BaseFont /Sans /FontDescriptor 6 0 R >>",
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"<< /Type /FontDescriptor /FontName /Sans /FontFile2 7 0 R >>",
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// A font program whose bytes read " k ", as Chromium and krilla write them.
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"<< /Length1 3 /Length 3 >>\nstream\n k \nendstream",
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],
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),
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("a comment", format!("{rgb} % 0 0 0 1 k"), "", vec![]),
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// A 3×1 gray image whose three bytes read " k ".
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("inline image data", format!("{rgb} q 10 0 0 10 0 0 cm BI /W 3 /H 1 /CS /G /BPC 8 ID k EI Q"), "", vec![]),
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("an ICC profile", rgb.to_owned(), "/ColorSpace << /CS0 [/ICCBased 5 0 R] >>", vec!["<< /N 3 /Length 3 >>\nstream\n k \nendstream"]),
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(
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"a mesh shading",
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format!("{rgb} /Sh0 sh"),
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"/Shading << /Sh0 5 0 R >>",
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vec![
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"<< /ShadingType 4 /ColorSpace /DeviceRGB /BitsPerCoordinate 8 /BitsPerComponent 8 /BitsPerFlag 8 /Decode [0 1 0 1 0 1 0 1 0 1] /BBox [0 0 10 10] /Length 3 >>\nstream\n k \nendstream",
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],
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),
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];
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for (what, content, resources, extra) in cases {
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let mut doc = drawing(content, resources, extra);
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assert!(!uses_cmyk(&doc), "a k in {what} was read as DeviceCMYK");
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let r = convert(&mut doc, Level::A2b).unwrap();
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assert_eq!(declared(&doc).output_intents, ["sRGB IEC61966-2.1"], "{what}: {:?}", r.fixed);
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}
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}
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/// Issue #2259: DeviceCMYK is found however the content sets it: `k`/`K` right before a delimiter, `cs`/`CS`
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/// with the space's name, or an inline image in `/CMYK` or indexed over it.
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#[test]
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fn device_colour_is_found_however_content_sets_it() {
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for content in [
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"0 0 0 1 k/GS0 gs 10 10 50 50 re f",
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"0 0 0 1 K[]0 d 10 10 m 50 50 l S",
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"/DeviceCMYK cs 0 0 0 1 sc 10 10 50 50 re f",
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"/DeviceCMYK CS 0 0 0 1 SC 10 10 m 50 50 l S",
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"q 10 0 0 10 0 0 cm BI /W 1 /H 1 /CS /CMYK /BPC 8 ID \u{0}\u{0}\u{0}\u{0} EI Q",
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"q 10 0 0 10 0 0 cm BI /W 1 /H 1 /ColorSpace /DeviceCMYK /BitsPerComponent 8 ID \u{0}\u{0}\u{0}\u{0} EI Q",
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"q 10 0 0 10 0 0 cm BI /W 1 /H 1 /CS [/I /DeviceCMYK 0 <00000000>] /BPC 8 ID \u{0} EI Q",
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] {
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assert!(uses_cmyk(&drawing(content, "", &[])), "{content:?}");
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}
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// A resource named like a device space's abbreviation is a resource, not that space.
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let named =
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drawing("/CMYK cs 1 sc 10 10 50 50 re f", "/ColorSpace << /CMYK [/ICCBased 5 0 R] >>", &["<< /N 1 /Length 0 >>\nstream\n\nendstream"]);
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assert!(!uses_cmyk(&named));
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}
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/// Issue #2259: content is not only the page's own stream: form XObjects (with `/Type /XObject`, as almost
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/// every writer gives them), appearance streams, tiling patterns and Type 3 glyphs draw too. A
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/// CMYK logo placed as a form must not get the document an sRGB output intent.
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#[test]
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fn device_colour_in_forms_patterns_and_glyphs_is_found() {
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let cmyk = "0.75 0 1 0 k 0 0 10 10 re f";
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let stream = |dict: &str| format!("<< {dict} /Length {} >>\nstream\n{cmyk}\nendstream", cmyk.len());
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let form = stream("/Type /XObject /Subtype /Form /BBox [0 0 10 10]");
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let appearance = stream("/BBox [0 0 10 10]");
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let pattern = stream("/Type /Pattern /PatternType 1 /PaintType 1 /TilingType 1 /BBox [0 0 10 10] /XStep 10 /YStep 10 /Resources << >>");
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let glyph = format!("<< /Length {} >>\nstream\n1 0 d0 {cmyk}\nendstream", cmyk.len() + 7);
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let cases: [(&str, Document); 4] = [
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("a form XObject", drawing("/Fm0 Do", "/XObject << /Fm0 5 0 R >>", &[&form])),
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(
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"an appearance stream without /Subtype",
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build(
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&[
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"<< /Type /Catalog /Pages 2 0 R >>",
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"<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 200 200] >>",
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"<< /Type /Page /Parent 2 0 R /Annots [4 0 R] >>",
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"<< /Type /Annot /Subtype /Square /Rect [0 0 10 10] /F 4 /P 3 0 R /AP << /N 5 0 R >> >>",
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&appearance,
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],
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"",
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),
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),
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("a tiling pattern", drawing("/Pattern cs /P0 scn 0 0 100 100 re f", "/Pattern << /P0 5 0 R >>", &[&pattern])),
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(
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"a Type 3 glyph in an inline font",
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drawing(
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"BT /T3 1 Tf (a) Tj ET",
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"/Font << /T3 << /Type /Font /Subtype /Type3 /FontBBox [0 0 10 10] /FontMatrix [1 0 0 1 0 0] /CharProcs << /a 5 0 R >> /Encoding << /Differences [97 /a] >> /FirstChar 97 /LastChar 97 /Widths [10] >> >>",
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&[&glyph],
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),
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),
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];
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for (what, mut doc) in cases {
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assert!(uses_cmyk(&doc), "DeviceCMYK in {what} wasn't found");
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let r = convert(&mut doc, Level::A2b).unwrap();
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assert!(declared(&doc).output_intents.is_empty(), "{what}: an sRGB output intent was added to a CMYK document: {:?}", r.fixed);
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}
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}
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Reference in New Issue
Block a user