Implemented FlatImage.IntersectionOfSegments() method with tests

Author: apdevelop

Src/ScreenGrid.Models.Tests/FlatImageTests.cs

@@ -133,6 +133,48 @@ public void FindZeroSegmentsTestSimpleSegment2()
             Assert.AreEqual(4, result[0].Item2);
         }
 
+        [Test]
+        public void IntersectionOfSegmentsFullIntersection()
+        {
+            var result = FlatImage.IntersectionOfSegments(
+                new Tuple<int, int>(1, 2),
+                new Tuple<int, int>(1, 2));
+            Assert.AreEqual(new Tuple<int, int>(1, 2), result);
+        }
+
+        [Test]
+        public void IntersectionOfSegmentsPartialIntersection()
+        {
+            var a = new Tuple<int, int>(1, 4);
+            var b = new Tuple<int, int>(2, 8);
+
+            Assert.AreEqual(new Tuple<int, int>(2, 4), FlatImage.IntersectionOfSegments(a, b));
+            Assert.AreEqual(new Tuple<int, int>(2, 4), FlatImage.IntersectionOfSegments(b, a));
+        }
+
+        [Test]
+        public void IntersectionOfSegmentsNoIntersection()
+        {
+            var result = FlatImage.IntersectionOfSegments(
+                new Tuple<int, int>(1, 2),
+                new Tuple<int, int>(4, 5));
+            Assert.IsNull(result);
+        }
+
+        [Test]
+        public void IntersectionOfSegments()
+        {
+            var result = FlatImage.IntersectionOfSegments(new[]
+                {
+                    new[] { new Tuple<int, int>(1, 2), new Tuple<int, int>(4, 6) },
+                    new[] { new Tuple<int, int>(1, 2), new Tuple<int, int>(5, 10) },
+                });
+
+            Assert.AreEqual(2, result.Count);
+            Assert.AreEqual(new Tuple<int, int>(1, 2), result[0]);
+            Assert.AreEqual(new Tuple<int, int>(5, 6), result[1]);
+        }
+
         private static FlatImage LoadFlatImageFromResource(string resourceName)
         {
             FlatImage flatImage;

Src/ScreenGrid.Models/FlatImage.cs

@@ -55,6 +55,8 @@ public UInt32[] GetHorizontalStripe(int iy)
             return result;
         }
 
+        // TODO: move to separate class
+
         public static UInt32[] GetDerivative(UInt32[] stripe)
         {
             var result = new UInt32[stripe.Length];
@@ -124,6 +126,56 @@ private static bool CheckSegmentLength(Tuple<int, int> segment, int minimalSegme
             return ((segment.Item2 - segment.Item1 + 1) >= minimalSegmentLength);
         }
 
+        public static Tuple<int, int> IntersectionOfSegments(Tuple<int, int> segment1, Tuple<int, int> segment2)
+        {
+            if ((segment1.Item1 > segment2.Item2) || (segment1.Item2 < segment2.Item1))
+            {
+                return null;
+            }
+            else
+            {
+                var start = Math.Max(segment1.Item1, segment2.Item1);
+                var end = Math.Min(segment1.Item2, segment2.Item2);
+                return new Tuple<int, int>(start, end);
+            }
+        }
+
+        public static IList<Tuple<int, int>> IntersectionOfSegments(IEnumerable<IList<Tuple<int, int>>> lines)
+        {
+            var sum = new List<Tuple<int, int>>();
+            foreach (var line in lines)
+            {
+                if (sum.Count == 0)
+                {
+                    sum.AddRange(line);
+                }
+                else
+                { 
+                    // Perform intersection checks
+                    var newSum = new List<Tuple<int, int>>();
+                    foreach (var segmentA in sum)
+                    {
+                        foreach (var segmentB in line)
+                        {
+                            var r = IntersectionOfSegments(segmentA, segmentB);
+                            if (r != null)
+                            {
+                                newSum.Add(r);
+                            }
+                        }
+                    }
+
+                    sum = newSum;
+                    if (sum.Count == 0)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return sum;
+        }
+
         public bool CompareWithFragment(FlatImage fragment, int startX, int startY)
         {
             for (var x = 0; x < fragment.Width; x++)