M11: PDF/A verify reports a halftone phase (HTP) in a graphics state (6.2.5)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pq7HyDBXygTf7jcqdsjcfn

crates/preflight/src/gstate.rs

@@ -2,6 +2,7 @@
 //! rely on.
 //!
 //! - no transfer function: no `/TR` entry, and `/TR2` only as `/Default` (ISO 32000-1 10.4);
+//! - no `/HTP` (halftone phase) entry, a PDF 1.2 key ISO 32000-1 no longer defines;
 //! - halftones of type 1 or 5 only, without a `/HalftoneName` (ISO 32000-1 10.5.5); the halftones
 //!   a type 5 halftone holds for its colorants are checked the same way;
 //! - a rendering intent (`/RI`) that is one of the four of ISO 32000-1 8.6.5.8, Table 70.
@@ -28,6 +29,8 @@ pub(crate) struct Findings {
     pub(crate) transfer: bool,
     /// A graphics state has a `/TR2` other than `/Default`.
     pub(crate) transfer2: bool,
+    /// A graphics state has an `/HTP`.
+    pub(crate) phase: bool,
     /// Halftone types other than 1 and 5, in order.
     pub(crate) halftone_types: BTreeSet<i64>,
     /// A halftone has a `/HalftoneName`.
@@ -96,6 +99,9 @@ impl Scan<'_> {
         if present(b"TR2").is_some_and(|f| f.as_name() != Some(b"Default")) {
             self.findings.transfer2 = true;
         }
+        if present(b"HTP").is_some() {
+            self.findings.phase = true;
+        }
         if let Some(ht) = present(b"HT")
             && let Some(ht) = ht.as_dict()
         {

crates/preflight/src/lib.rs

@@ -124,6 +124,7 @@ pub const WORDINGS: &[&str] = &[
     "The document has document-level JavaScript",
     "A graphics state has a transfer function (TR)",
     "A graphics state has a transfer function (TR2) other than Default",
+    "A graphics state has a halftone phase (HTP)",
     "A halftone has type {}: only types 1 and 5 are allowed",
     "A halftone has a HalftoneName",
     "A graphics state has the rendering intent {}, which isn't a standard one",
@@ -529,6 +530,9 @@ pub fn verify(doc: &Document, level: Level) -> Vec<Issue> {
     if gs.transfer2 {
         issue("6.2.5", "A graphics state has a transfer function (TR2) other than Default", None, None, false);
     }
+    if gs.phase {
+        issue("6.2.5", "A graphics state has a halftone phase (HTP)", None, None, false);
+    }
     for kind in gs.halftone_types {
         issue("6.2.5", "A halftone has type {}: only types 1 and 5 are allowed", Some(kind.to_string()), None, false);
     }

crates/preflight/src/tests.rs

@@ -521,6 +521,7 @@ fn extended_graphics_states_are_checked() {
     assert_eq!(gs("/A 6 0 R"), [tr]);
     assert_eq!(gs("/A << /TR2 4 0 R >>"), [tr2]);
     assert_eq!(gs("/A << /TR2 /Identity >>"), [tr2]);
+    assert_eq!(gs("/A << /HTP [0 1] >>"), ["A graphics state has a halftone phase (HTP)"]);
     // Halftones: the type, also of a type 5 halftone's colorants and of a stream, and the name.
     assert_eq!(gs("/A << /HT << /HalftoneType 6 >> >>"), ["A halftone has type 6: only types 1 and 5 are allowed"]);
     assert_eq!(gs("/A << /HT 7 0 R >>"), ["A halftone has type 6: only types 1 and 5 are allowed"]);