pdftract/notes/pdftract-2hag2.md

Verification Note: pdftract-2hag2

Bead: Signal evaluator: all_tr3_with_full_page_image (Tr=3 + image >= 95% page -> BrokenVector definitive)

Summary

The all_tr3_with_full_page_image signal evaluator was implemented in commit 39ca6a3 as part of bead pdftract-2b7ff (image_coverage_fraction). The implementation is correct and all acceptance criteria are met.

Implementation Location

• File: crates/pdftract-core/src/classify.rs
• Function: pub fn all_tr3_with_full_page_image(ctx: &PageContext) -> Option<Vote> (lines 339-357)
• Tests: Lines 2459-2695

Acceptance Criteria Verification

1. text_op_count=10, tr3_op_count=10, full_page_image=true → Some(Vote { 0.99, BrokenVector })

• Test: test_all_tr3_with_full_page_image_exact_match (line 2462)
• Status: PASS

2. text_op_count=10, tr3_op_count=5 → None (mix of Tr=3 and visible)

• Test: test_all_tr3_with_full_page_image_mixed_tr3 (line 2516)
• Status: PASS

3. text_op_count=0 → None (no text)

• Test: test_all_tr3_with_full_page_image_no_text (line 2532)
• Status: PASS

4. full_page_image=false → None

• Test: test_all_tr3_with_full_page_image_no_full_page_image (line 2548)
• Status: PASS

5. Unit tests

• Total tests: 10 tests covering all edge cases
• Additional tests:
  • Exactly 95% coverage (threshold edge case)
  • Just below 95% threshold
  • Multiple images (one large enough)
  • Zero page area (division by zero guard)
  • Empty image areas
  • Definitive short-circuit verification
  • Standard US Letter and A4 page sizes
• Status: PASS

Implementation Review

Signature

pub fn all_tr3_with_full_page_image(ctx: &PageContext) -> Option<Vote>

Status: ✓ Correct

Logic

let all_tr3 = ctx.text_op_count > 0 && ctx.tr3_op_count == ctx.text_op_count;
let page_area = ctx.width * ctx.height;
let full_page_image = if page_area > 0.0 {
    ctx.image_xobject_areas.iter().any(|&area| area / page_area >= 0.95)
} else {
    false
};
if all_tr3 && full_page_image {
    return Some(Vote::broken_vector(0.99));
}
None

Status: ✓ Correct

Key Features

• All text operators must be Tr=3 (not just some) - enforced by tr3_op_count == text_op_count
• Single image XObject covering >= 95% of page area - uses iter().any() to check if ANY image meets threshold
• Definitive strength 0.99 for short-circuit behavior in PageClassifier
• Division by zero guard when page_area <= 0.0
• Returns None for all non-matching cases

Integration

The signal is integrated into the PageClassifier via InvisibleTextWithImageSignal (lines 195-207):

struct InvisibleTextWithImageSignal;

impl SignalEvaluator for InvisibleTextWithImageSignal {
    fn evaluate(&self, ctx: &PageContext) -> Option<Vote> {
        all_tr3_with_full_page_image(ctx)
    }

    fn name(&self) -> &'static str {
        "all_tr3_with_full_page_image"
    }
}

References

• EC-12: Tr=3 + full-page-image is a deterministic BrokenVector signal
• Plan section: Phase 5.1.2
• Commit: 39ca6a3 (feat(pdftract-2b7ff): implement image_coverage_fraction signal evaluator)

Conclusion

PASS: All acceptance criteria are met. The implementation is correct, complete, and fully tested.