7b2759b365
The image_coverage_fraction signal evaluator was already implemented in crates/pdftract-core/src/classify.rs. All acceptance criteria verified: - 90% single image → Scanned with strength 0.85 - 50% multiple images → None (below threshold) - No images → None - Overlapping images clamped to 1.0 Implementation uses sum (not union) with documented trade-off, revisit with Klee's algorithm if accuracy demands.
56 lines
2.3 KiB
Markdown
56 lines
2.3 KiB
Markdown
# Verification Note: pdftract-2b7ff
|
|
|
|
## Bead: image_coverage_fraction signal evaluator
|
|
|
|
## Status: PASS ✅
|
|
|
|
The `image_coverage_fraction` signal evaluator was already implemented in the codebase at `/home/coding/pdftract/crates/pdftract-core/src/classify.rs` (lines 359-413).
|
|
|
|
## Implementation Details
|
|
|
|
### Signature
|
|
```rust
|
|
pub fn image_coverage_fraction(ctx: &PageContext) -> Option<Vote>
|
|
```
|
|
|
|
### Algorithm
|
|
1. Compute page area: `page_area_pt2 = ctx.width * ctx.height`
|
|
2. Guard against zero/negative page area (returns `None`)
|
|
3. Sum all `image_xobject_areas` to get total image coverage
|
|
4. Compute coverage fraction: `total_image_area / page_area_pt2`
|
|
5. Clamp to `[0.0, 1.0]` to handle overlapping images defensively
|
|
6. If `coverage_fraction > 0.85`: return `Some(Vote::scanned(0.85))`
|
|
|
|
### Trade-offs Documented in Code
|
|
The implementation uses `sum` instead of `union` for simplicity, with a clear comment noting:
|
|
- 5 overlapping copies of one image = sum of 5x area but union is 1x area
|
|
- This is acceptable for the 0.85 threshold (conservative signal)
|
|
- Revisit with Klee's algorithm (~O(N log N)) if accuracy demands
|
|
|
|
## Acceptance Criteria Verification
|
|
|
|
| AC | Status | Notes |
|
|
|---|--------|-------|
|
|
| Page with one image covering 90% area → Some(Vote { 0.85, Scanned }) | ✅ PASS | Lines 2698-2713 test this exact case |
|
|
| Page with multiple small images totaling 50% → None | ✅ PASS | Lines 2715-2730 test this exact case |
|
|
| Page with no images → None | ✅ PASS | Lines 2732-2743 test this exact case |
|
|
| Coverage clamped to 1.0 on overlapping images | ✅ PASS | Lines 2745-2766 test 5x overlapping images |
|
|
|
|
## Additional Tests Verified
|
|
|
|
| Test Case | Status |
|
|
|-----------|--------|
|
|
| Exactly 85% threshold (just above) | ✅ PASS (lines 2769-2783) |
|
|
| Just below 85% threshold | ✅ PASS (lines 2785-2797) |
|
|
| Zero page area | ✅ PASS (lines 2799-2810) |
|
|
| Negative page area | ✅ PASS (lines 2812-2823) |
|
|
| Multiple images totaling 90% | ✅ PASS (lines 2839-2856) |
|
|
|
|
## Conclusion
|
|
|
|
The implementation is complete, correct, and thoroughly tested. All acceptance criteria pass. The bead is ready to close.
|
|
|
|
## Files Reviewed
|
|
|
|
- `/home/coding/pdftract/crates/pdftract-core/src/classify.rs` - Main implementation (lines 359-413)
|
|
- `/home/coding/pdftract/crates/pdftract-core/src/classify.rs` - Tests (lines 2696-2889)
|