Merge pull request #4066 from dotCooCoo/fix/flat-logo-anchor-limit-counts-kept-outlines

Image Trace: Flat Logo counts only the outlines it keeps toward the anchor limit

crates/trace/src/logo/pipeline.rs

@@ -296,6 +296,28 @@ fn shape_subpaths(s: &Shape, map: &ToSource) -> Vec<SubPath> {
     subs
 }
 
+/// A shape's subpaths in source pixels, with no outline or hole that paints nothing.
+struct Kept {
+    class: usize,
+    area: f64,
+    subs: Vec<SubPath>,
+}
+
+/// Adds `s` to `kept` unless it paints nothing, and counts the anchors of the subpaths it keeps
+/// in `anchors_made`: the trace is too complex once they come to more than `max_anchors`.
+fn keep_shape(s: &Shape, map: &ToSource, kept: &mut Vec<Kept>, anchors_made: &mut usize, max_anchors: usize) -> Result<(), TraceError> {
+    let subs = shape_subpaths(s, map);
+    if subs.is_empty() {
+        return Ok(());
+    }
+    *anchors_made = anchors_made.saturating_add(subs.iter().map(|sp| sp.anchors.len()).sum::<usize>());
+    if *anchors_made > max_anchors {
+        return Err(TraceError::TooComplex { max: max_anchors });
+    }
+    kept.push(Kept { class: s.class, area: s.area, subs });
+    Ok(())
+}
+
 /// A hard-edged source (a GIF, say) has no anti-aliasing to read an edge position from, and its
 /// outlines would follow the pixel staircase. Blurring the coverage by under a pixel gives the
 /// outline a smooth edge to find. Sources with plenty of blended edge pixels are left alone.
@@ -449,7 +471,8 @@ pub(crate) fn trace_logo(img: &Raster, params: &TraceParams, max_anchors: usize)
     // `noise` is in source pixels (areas under noise/10 are ignored), whatever the working size.
     let min_area = ((f64::from(params.noise) / 10.0) / (factor * factor) as f64).max(0.3);
     let mut stats = Stats::default();
-    let mut shapes: Vec<Shape> = Vec::new();
+    let to_source = ToSource { factor: factor as f64, work: (w, h), source: (w0, h0) };
+    let mut shapes: Vec<Kept> = Vec::new();
     let mut anchors_made = 0usize;
     for class in 0..=white {
         if class == white && params.ignore_white {
@@ -465,6 +488,10 @@ pub(crate) fn trace_logo(img: &Raster, params: &TraceParams, max_anchors: usize)
             if a2.abs() / 2.0 < min_area {
                 continue;
             }
+            // Holes are cut only under Ignore White; otherwise white and the other colors are traced as their own shapes.
+            if a2 >= 0.0 && !params.ignore_white {
+                continue;
+            }
             // More real outlines than we will fit is refused, not silently truncated.
             if outers.len() + holes.len() >= MAX_LOOPS_PER_CLASS {
                 return Err(TraceError::TooComplex { max: max_anchors });
@@ -489,28 +516,19 @@ pub(crate) fn trace_logo(img: &Raster, params: &TraceParams, max_anchors: usize)
             let Some(outer) = fit_outline(&pts, &style, &mut stats) else { continue };
             let hole_fits: Vec<Vec<Cubic>> =
                 holes.iter().zip(&owner).filter(|(_, o)| **o == Some(idx)).filter_map(|(hole, _)| fit_outline(hole, &style, &mut stats)).collect();
-            anchors_made += outer.len() + hole_fits.iter().map(Vec::len).sum::<usize>();
-            if anchors_made > max_anchors {
-                return Err(TraceError::TooComplex { max: max_anchors });
-            }
-            shapes.push(Shape { class, area, outer, holes: hole_fits });
+            keep_shape(&Shape { class, area, outer, holes: hole_fits }, &to_source, &mut shapes, &mut anchors_made, max_anchors)?;
         }
     }
     // Painter's order: biggest shapes first, so smaller ones sit on top of what they belong to.
     shapes.sort_by(|a, b| b.area.total_cmp(&a.area).then(a.class.cmp(&b.class)));
-    let to_source = ToSource { factor: factor as f64, work: (w, h), source: (w0, h0) };
     let mut out = TraceResult { worked_at: (factor > 1).then_some((w as u32, h as u32)), ..TraceResult::default() };
     for s in shapes {
         let color = palette.get(s.class).copied().unwrap_or([255, 255, 255]);
-        let subs = shape_subpaths(&s, &to_source);
-        if subs.is_empty() {
-            continue;
-        }
         if !out.palette.contains(&color) {
             out.palette.push(color);
         }
         out.paths.push(TracedPath {
-            path: PathData::new(subs),
+            path: PathData::new(s.subs),
             color,
             pixels: (s.area * (factor * factor) as f64) as usize,
             stroke: None,
@@ -563,4 +581,17 @@ mod tests {
         };
         assert!(shape_subpaths(&shape, &map).is_empty());
     }
+
+    #[test]
+    fn the_anchor_limit_counts_only_the_subpaths_kept() {
+        let map = ToSource { factor: 1.0, work: (40, 40), source: (40, 40) };
+        let square = || polygon(&[(5.0, 5.0), (35.0, 5.0), (35.0, 35.0), (5.0, 35.0)]);
+        let with_flat_hole = Shape { class: 0, area: 900.0, outer: square(), holes: vec![polygon(&[(10.0, 20.0), (20.0, 20.0)])] };
+        let flat_outline = Shape { class: 0, area: 1.0, outer: polygon(&[(5.0, 5.0), (35.0, 5.0)]), holes: vec![square()] };
+        let (mut kept, mut anchors_made) = (Vec::new(), 0usize);
+        assert!(keep_shape(&with_flat_hole, &map, &mut kept, &mut anchors_made, 4).is_ok());
+        assert!(keep_shape(&flat_outline, &map, &mut kept, &mut anchors_made, 4).is_ok());
+        assert_eq!((kept.len(), anchors_made), (1, 4));
+        assert!(matches!(keep_shape(&with_flat_hole, &map, &mut kept, &mut anchors_made, 4), Err(TraceError::TooComplex { max: 4 })));
+    }
 }

crates/trace/src/logo/tests.rs

@@ -364,6 +364,24 @@ fn too_many_outlines_are_refused_not_silently_truncated() {
     assert!(res.paths.is_empty());
 }
 
+#[test]
+fn holes_that_are_not_cut_do_not_count_towards_the_outline_limit() {
+    // A blue field with 625 holes, each filled with red, white or green: more holes than the limit, fewer of each fill.
+    const GREEN: [u8; 3] = [40, 170, 60];
+    let img = render(125, 125, 0.0, |x, y| {
+        let (cx, cy) = (x.rem_euclid(5.0), y.rem_euclid(5.0));
+        if (1.0..4.0).contains(&cx) && (1.0..4.0).contains(&cy) {
+            Some([RED, [255, 255, 255], GREEN][((x / 5.0) as usize + (y / 5.0) as usize) % 3])
+        } else {
+            Some(BLUE)
+        }
+    });
+    let res = trace_within(&img, &logo_params(), 1_000_000).expect("trace");
+    assert!(res.paths.iter().any(|p| near(p.color, BLUE, 3)), "the blue field is traced");
+    // Under Ignore White the holes are cut, so they count.
+    assert!(matches!(trace_within(&img, &TraceParams { ignore_white: true, ..logo_params() }, 1_000_000), Err(TraceError::TooComplex { .. })));
+}
+
 #[test]
 fn a_large_odd_sized_image_never_overshoots_its_edges() {
     // 1025 wide: the last working pixel is narrower than the others.