add test cases for rectangle transforms

our bounding rectangle values still seem to be wrong for rotated letters. this change adds some test cases for common transformation matrix operations on a rectangle, scale, translate and rotate.

src/UglyToad.PdfPig.Core/TransformationMatrix.cs

@@ -22,6 +22,51 @@
         public static TransformationMatrix GetTranslationMatrix(double x, double y) => new TransformationMatrix(1, 0, 0,
             0, 1, 0,
             x, y, 1);
+        
+        /// <summary>
+        /// Create a new <see cref="TransformationMatrix"/> with the X and Y scaling values set.
+        /// </summary>
+        public static TransformationMatrix GetScaleMatrix(double scaleX, double scaleY) => new TransformationMatrix(scaleX, 0, 0,
+            0, scaleY, 0,
+            0, 0, 1);
+
+        /// <summary>
+        /// Create a new <see cref="TransformationMatrix"/> with the X and Y scaling values set.
+        /// </summary>
+        public static TransformationMatrix GetRotationMatrix(double degreesCounterclockwise)
+        {
+            double cos;
+            double sin;
+
+            switch (degreesCounterclockwise)
+            {
+                case 0:
+                case 360:
+                    cos = 1;
+                    sin = 0;
+                    break;
+                case 90:
+                    cos = 0;
+                    sin = 1;
+                    break;
+                case 180:
+                    cos = -1;
+                    sin = 0;
+                    break;
+                case 270:
+                    cos = 0;
+                    sin = -1;
+                    break;
+                default:
+                    cos = Math.Cos(degreesCounterclockwise * (Math.PI / 180));
+                    sin = Math.Sin(degreesCounterclockwise * (Math.PI / 180));
+                    break;
+            }
+
+            return new TransformationMatrix(cos, sin, 0,
+                -sin, cos, 0,
+                0, 0, 1);
+        }
 
         private readonly double row1;
         private readonly double row2;

src/UglyToad.PdfPig.Tests/Geometry/PdfRectangleTests.cs

@@ -6,24 +6,32 @@
 
     public class PdfRectangleTests
     {
+        private static readonly DoubleComparer DoubleComparer = new DoubleComparer(3);
+        private static readonly PointComparer PointComparer = new PointComparer(DoubleComparer);
+        private static readonly PdfRectangle UnitRectangle = new PdfRectangle(new PdfPoint(0, 0), new PdfPoint(1, 1));
+
+        [Fact]
         public void Area()
         {
             PdfRectangle rectangle = new PdfRectangle(10, 10, 20, 20);
             Assert.Equal(100d, rectangle.Area);
 
             PdfRectangle rectangle1 = new PdfRectangle(149.95376d, 687.13456d, 451.73539d, 1478.4997d);
-            Assert.Equal(238819.4618743782d, rectangle1.Area);
+            Assert.Equal(238819.4618743782d, rectangle1.Area, DoubleComparer);
         }
 
+        [Fact]
         public void Centroid()
         {
             PdfRectangle rectangle = new PdfRectangle(10, 10, 20, 20);
             Assert.Equal(new PdfPoint(15, 15), rectangle.Centroid);
 
             PdfRectangle rectangle1 = new PdfRectangle(149.95376d, 687.13456d, 451.73539d, 1478.4997d);
-            Assert.Equal(new PdfPoint(300.844575d, 1082.81713d), rectangle1.Centroid);
+            Assert.Equal(new PdfPoint(300.844575d, 1082.81713d), rectangle1.Centroid,
+                PointComparer);
         }
 
+        [Fact]
         public void Intersect()
         {
             PdfRectangle rectangle = new PdfRectangle(10, 10, 20, 20);
@@ -38,6 +46,7 @@
             Assert.Equal(rectangle3, rectangle1.Intersect(rectangle3));
         }
 
+        [Fact]
         public void IntersectsWith()
         {
             PdfRectangle rectangle = new PdfRectangle(10, 10, 20, 20);
@@ -55,6 +64,7 @@
             Assert.False(rectangle1.IntersectsWith(rectangle4)); // special case where they share one border
         }
 
+        [Fact]
         public void Contains()
         {
             PdfRectangle rectangle = new PdfRectangle(10, 10, 20, 20);
@@ -63,5 +73,85 @@
             Assert.True(rectangle.Contains(new PdfPoint(10, 15), true));
             Assert.False(rectangle.Contains(new PdfPoint(100, 100), true));
         }
+
+        [Fact]
+        public void Translate()
+        {
+            var tm = TransformationMatrix.GetTranslationMatrix(5, 7);
+
+            var translated = tm.Transform(UnitRectangle);
+
+            Assert.Equal(new PdfPoint(5, 7), translated.BottomLeft);
+            Assert.Equal(new PdfPoint(6, 7), translated.BottomRight);
+            Assert.Equal(new PdfPoint(5, 8), translated.TopLeft);
+            Assert.Equal(new PdfPoint(6, 8), translated.TopRight);
+
+            Assert.Equal(1, translated.Width);
+            Assert.Equal(1, translated.Height);
+        }
+
+        [Fact]
+        public void Scale()
+        {
+            var tm = TransformationMatrix.GetScaleMatrix(3, 5);
+
+            var scaled = tm.Transform(UnitRectangle);
+
+            Assert.Equal(new PdfPoint(0, 0), scaled.BottomLeft);
+            Assert.Equal(new PdfPoint(3, 0), scaled.BottomRight);
+            Assert.Equal(new PdfPoint(0, 5), scaled.TopLeft);
+            Assert.Equal(new PdfPoint(3, 5), scaled.TopRight);
+
+            Assert.Equal(3, scaled.Width);
+            Assert.Equal(5, scaled.Height);
+        }
+
+        [Fact]
+        public void Rotate360()
+        {
+            var tm = TransformationMatrix.GetRotationMatrix(360);
+
+            var rotated = tm.Transform(UnitRectangle);
+
+            Assert.Equal(new PdfPoint(0, 0), rotated.BottomLeft);
+            Assert.Equal(new PdfPoint(1, 0), rotated.BottomRight);
+            Assert.Equal(new PdfPoint(0, 1), rotated.TopLeft);
+            Assert.Equal(new PdfPoint(1, 1), rotated.TopRight);
+
+            Assert.Equal(1, rotated.Width);
+            Assert.Equal(1, rotated.Height);
+        }
+
+        [Fact]
+        public void Rotate90()
+        {
+            var tm = TransformationMatrix.GetRotationMatrix(90);
+
+            var rotated = tm.Transform(UnitRectangle);
+
+            Assert.Equal(new PdfPoint(0, 0), rotated.BottomLeft);
+            Assert.Equal(new PdfPoint(0, 1), rotated.BottomRight);
+            Assert.Equal(new PdfPoint(-1, 0), rotated.TopLeft);
+            Assert.Equal(new PdfPoint(-1, 1), rotated.TopRight);
+
+            Assert.Equal(1, rotated.Width);
+            Assert.Equal(-1, rotated.Height);
+        }
+
+        [Fact]
+        public void Rotate180()
+        {
+            var tm = TransformationMatrix.GetRotationMatrix(180);
+
+            var rotated = tm.Transform(UnitRectangle);
+
+            Assert.Equal(new PdfPoint(0, 0), rotated.BottomLeft);
+            Assert.Equal(new PdfPoint(-1, 0), rotated.BottomRight);
+            Assert.Equal(new PdfPoint(0, -1), rotated.TopLeft);
+            Assert.Equal(new PdfPoint(-1, -1), rotated.TopRight);
+
+            Assert.Equal(-1, rotated.Width);
+            Assert.Equal(-1, rotated.Height);
+        }
     }
 }