feat(io): add border detection with angular tolerance and zone markers (phase 2)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.IO/TitleBlockDetector.cs

@@ -18,6 +18,7 @@ namespace OpenNest.IO
         {
             var flagged = new HashSet<Guid>();
             DetectByLayerName(entities, flagged);
+            DetectBorder(entities, flagged);
             return flagged;
         }
 
@@ -29,5 +30,101 @@ namespace OpenNest.IO
                     flagged.Add(entity.Id);
             }
         }
+
+        private static void DetectBorder(List<Entity> entities, HashSet<Guid> flagged)
+        {
+            var lines = entities.OfType<Line>().Where(l => !flagged.Contains(l.Id)).ToList();
+            if (lines.Count < 4) return;
+
+            var bounds = entities.GetBoundingBox();
+            if (bounds == null || bounds.Area() < OpenNest.Math.Tolerance.Epsilon) return;
+
+            var borderCount = 0;
+            foreach (var line in lines)
+            {
+                if (IsBorderLine(line, bounds))
+                {
+                    flagged.Add(line.Id);
+                    borderCount++;
+                }
+            }
+
+            if (borderCount >= 2)
+                DetectZoneMarkers(lines, bounds, flagged);
+        }
+
+        private static bool IsBorderLine(Line line, Box bounds)
+        {
+            var dx = line.EndPoint.X - line.StartPoint.X;
+            var dy = line.EndPoint.Y - line.StartPoint.Y;
+            var length = System.Math.Sqrt(dx * dx + dy * dy);
+            var angleRad = System.Math.Atan2(System.Math.Abs(dy), System.Math.Abs(dx));
+            var angularTolerance = OpenNest.Math.Angle.ToRadians(2.0);
+            var positionTolerance = System.Math.Max(bounds.Length, bounds.Width) * 0.01;
+
+            var isHorizontal = angleRad < angularTolerance;
+            var isVertical = System.Math.Abs(angleRad - System.Math.PI / 2) < angularTolerance;
+
+            if (!isHorizontal && !isVertical) return false;
+
+            var minSpan = isHorizontal ? bounds.Length * 0.8 : bounds.Width * 0.8;
+            if (length < minSpan) return false;
+
+            if (isHorizontal)
+            {
+                var midY = (line.StartPoint.Y + line.EndPoint.Y) / 2;
+                return System.Math.Abs(midY - bounds.Bottom) < positionTolerance
+                    || System.Math.Abs(midY - bounds.Top) < positionTolerance;
+            }
+            else
+            {
+                var midX = (line.StartPoint.X + line.EndPoint.X) / 2;
+                return System.Math.Abs(midX - bounds.Left) < positionTolerance
+                    || System.Math.Abs(midX - bounds.Right) < positionTolerance;
+            }
+        }
+
+        private static void DetectZoneMarkers(List<Line> lines, Box bounds, HashSet<Guid> flagged)
+        {
+            var positionTolerance = System.Math.Max(bounds.Length, bounds.Width) * 0.01;
+            var maxTickLength = System.Math.Max(bounds.Length, bounds.Width) * 0.05;
+            var angularTolerance = OpenNest.Math.Angle.ToRadians(2.0);
+
+            foreach (var line in lines)
+            {
+                if (flagged.Contains(line.Id)) continue;
+
+                var dx = line.EndPoint.X - line.StartPoint.X;
+                var dy = line.EndPoint.Y - line.StartPoint.Y;
+                var length = System.Math.Sqrt(dx * dx + dy * dy);
+
+                if (length > maxTickLength || length < OpenNest.Math.Tolerance.Epsilon) continue;
+
+                var angleRad = System.Math.Atan2(System.Math.Abs(dy), System.Math.Abs(dx));
+                var isVertical = System.Math.Abs(angleRad - System.Math.PI / 2) < angularTolerance;
+                var isHorizontal = angleRad < angularTolerance;
+
+                if (!isVertical && !isHorizontal) continue;
+
+                var touchesEdge = false;
+                if (isVertical)
+                {
+                    var minY = System.Math.Min(line.StartPoint.Y, line.EndPoint.Y);
+                    var maxY = System.Math.Max(line.StartPoint.Y, line.EndPoint.Y);
+                    touchesEdge = System.Math.Abs(minY - bounds.Bottom) < positionTolerance
+                               || System.Math.Abs(maxY - bounds.Top) < positionTolerance;
+                }
+                else if (isHorizontal)
+                {
+                    var minX = System.Math.Min(line.StartPoint.X, line.EndPoint.X);
+                    var maxX = System.Math.Max(line.StartPoint.X, line.EndPoint.X);
+                    touchesEdge = System.Math.Abs(minX - bounds.Left) < positionTolerance
+                               || System.Math.Abs(maxX - bounds.Right) < positionTolerance;
+                }
+
+                if (touchesEdge)
+                    flagged.Add(line.Id);
+            }
+        }
     }
 }