Add Skew, Enhance Rotate

Former-commit-id: 55c3fee46aa082cc2cca3232580ed42d6d40a1e1
Former-commit-id: ab1b89f66aca40b6d2afe262ab937d768cae67af
Former-commit-id: ef13eccfc48a91a3adc99eaf0b746486d069bac1

README.md

@@ -92,9 +92,10 @@ git clone https://github.com/JimBobSquarePants/ImageProcessor
  - [x] Rectangular Crop
  - [ ] Elliptical Crop
  - [x] Entropy Crop
-- Rotation
+- Rotation/Skew
  - [x] Flip (90, 270, FlipType etc)
- - [x] Rotate by angle
+ - [x] Rotate by angle and center point.
+ - [x] Skew by x/y angles and center point.
 - ColorMatrix operations (Uses Matrix4x4)
  - [x] BlackWhite
  - [x] Greyscale BT709

src/ImageProcessorCore/Numerics/Point.cs

@@ -171,6 +171,21 @@ namespace ImageProcessorCore
             return new Point(Vector2.Transform(point.backingVector, Matrix3x2.CreateRotation(radians, origin.backingVector)));
         }
 
+        /// <summary>
+        /// Skews a point around a given origin by the specified angles in degrees.
+        /// </summary>
+        /// <param name="point">The point to rotate</param>
+        /// <param name="origin">The center point to rotate around.</param>
+        /// <param name="degreesX">The x-angle in degrees.</param>
+        /// <param name="degreesY">The y-angle in degrees.</param>
+        /// <returns></returns>
+        public static Point Skew(Point point, Point origin, float degreesX, float degreesY)
+        {
+            float radiansX = (float)ImageMaths.DegreesToRadians(degreesX);
+            float radiansY = (float)ImageMaths.DegreesToRadians(degreesY);
+            return new Point(Vector2.Transform(point.backingVector, Matrix3x2.CreateSkew(degreesX, degreesY, origin.backingVector)));
+        }
+
         /// <inheritdoc/>
         public override int GetHashCode()
         {

src/ImageProcessorCore/Samplers/ImageSamplerExtensions.cs

@@ -170,13 +170,26 @@ namespace ImageProcessorCore.Samplers
         /// <summary>
         /// Rotates an image by the given angle in degrees.
         /// </summary>
-        /// <param name="source">The image to resize.</param>
+        /// <param name="source">The image to rotate.</param>
         /// <param name="degrees">The angle in degrees to perform the rotation.</param>
         /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
         /// <returns>The <see cref="Image"/></returns>
         public static Image Rotate(this Image source, float degrees, ProgressEventHandler progressHandler = null)
         {
-            Rotate processor = new Rotate { Angle = degrees };
+            return Rotate(source, degrees, Rectangle.Center(source.Bounds), progressHandler);
+        }
+
+        /// <summary>
+        /// Rotates an image by the given angle in degrees around the given center point.
+        /// </summary>
+        /// <param name="source">The image to rotate.</param>
+        /// <param name="degrees">The angle in degrees to perform the rotation.</param>
+        /// <param name="center">The center point at which to skew the image.</param>
+        /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
+        /// <returns>The <see cref="Image"/></returns>
+        public static Image Rotate(this Image source, float degrees, Point center, ProgressEventHandler progressHandler = null)
+        {
+            Rotate processor = new Rotate { Angle = degrees, Center = center };
             processor.OnProgress += progressHandler;
 
             try
@@ -192,7 +205,7 @@ namespace ImageProcessorCore.Samplers
         /// <summary>
         /// Rotates and flips an image by the given instructions.
         /// </summary>
-        /// <param name="source">The image to resize.</param>
+        /// <param name="source">The image to rotate, flip, or both.</param>
         /// <param name="rotateType">The <see cref="RotateType"/> to perform the rotation.</param>
         /// <param name="flipType">The <see cref="FlipType"/> to perform the flip.</param>
         /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
@@ -211,5 +224,42 @@ namespace ImageProcessorCore.Samplers
                 processor.OnProgress -= progressHandler;
             }
         }
+
+        /// <summary>
+        /// Skews an image by the given angles in degrees.
+        /// </summary>
+        /// <param name="source">The image to skew.</param>
+        /// <param name="degreesX">The angle in degrees to perform the rotation along the x-axis.</param>
+        /// <param name="degreesY">The angle in degrees to perform the rotation along the y-axis.</param>
+        /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
+        /// <returns>The <see cref="Image"/></returns>
+        public static Image Skew(this Image source, float degreesX, float degreesY, ProgressEventHandler progressHandler = null)
+        {
+            return Skew(source, degreesX, degreesY, Rectangle.Center(source.Bounds), progressHandler);
+        }
+
+        /// <summary>
+        /// Skews an image by the given angles in degrees around the given center point.
+        /// </summary>
+        /// <param name="source">The image to skew.</param>
+        /// <param name="degreesX">The angle in degrees to perform the rotation along the x-axis.</param>
+        /// <param name="degreesY">The angle in degrees to perform the rotation along the y-axis.</param>
+        /// <param name="center">The center point at which to skew the image.</param>
+        /// <param name="progressHandler">A delegate which is called as progress is made processing the image.</param>
+        /// <returns>The <see cref="Image"/></returns>
+        public static Image Skew(this Image source, float degreesX, float degreesY, Point center, ProgressEventHandler progressHandler = null)
+        {
+            Skew processor = new Skew { AngleX = degreesX, AngleY = degreesY, Center = center };
+            processor.OnProgress += progressHandler;
+
+            try
+            {
+                return source.Process(source.Width, source.Height, source.Bounds, source.Bounds, processor);
+            }
+            finally
+            {
+                processor.OnProgress -= progressHandler;
+            }
+        }
     }
 }

src/ImageProcessorCore/Samplers/Rotate.cs

@@ -8,7 +8,7 @@ namespace ImageProcessorCore.Samplers
     using System.Threading.Tasks;
 
     /// <summary>
-    /// Provides methods that allow the rotating of images using various algorithms.
+    /// Provides methods that allow the rotating of images.
     /// </summary>
     public class Rotate : ImageSampler
     {
@@ -43,6 +43,11 @@ namespace ImageProcessorCore.Samplers
             }
         }
 
+        /// <summary>
+        /// Gets or sets the center point.
+        /// </summary>
+        public Point Center { get; set; }
+
         /// <inheritdoc/>
         protected override void Apply(ImageBase target, ImageBase source, Rectangle targetRectangle, Rectangle sourceRectangle, int startY, int endY)
         {
@@ -51,7 +56,7 @@ namespace ImageProcessorCore.Samplers
             int startX = targetRectangle.X;
             int endX = targetRectangle.Right;
             float negativeAngle = -this.angle;
-            Point centre = Rectangle.Center(sourceRectangle);
+            Point centre = this.Center == Point.Empty ? Rectangle.Center(sourceRectangle) : this.Center;
 
             // Scaling factors
             float widthFactor = source.Width / (float)target.Width;

src/ImageProcessorCore/Samplers/Skew.cs

@@ -0,0 +1,124 @@
+// <copyright file="Skew.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageProcessorCore.Samplers
+{
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// Provides methods that allow the skewing of images.
+    /// </summary>
+    public class Skew : ImageSampler
+    {
+        /// <summary>
+        /// The angle of rotation along the x-axis.
+        /// </summary>
+        private float angleX;
+
+        /// <summary>
+        /// The angle of rotation along the y-axis.
+        /// </summary>
+        private float angleY;
+
+        /// <summary>
+        /// Gets or sets the angle of rotation along the x-axis in degrees.
+        /// </summary>
+        public float AngleX
+        {
+            get
+            {
+                return this.angleX;
+            }
+
+            set
+            {
+                if (value > 360)
+                {
+                    value -= 360;
+                }
+
+                if (value < 0)
+                {
+                    value += 360;
+                }
+
+                this.angleX = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the angle of rotation along the y-axis in degrees.
+        /// </summary>
+        public float AngleY
+        {
+            get
+            {
+                return this.angleY;
+            }
+
+            set
+            {
+                if (value > 360)
+                {
+                    value -= 360;
+                }
+
+                if (value < 0)
+                {
+                    value += 360;
+                }
+
+                this.angleY = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the center point.
+        /// </summary>
+        public Point Center { get; set; }
+
+        /// <inheritdoc/>
+        protected override void Apply(ImageBase target, ImageBase source, Rectangle targetRectangle, Rectangle sourceRectangle, int startY, int endY)
+        {
+            int targetY = targetRectangle.Y;
+            int targetBottom = targetRectangle.Bottom;
+            int startX = targetRectangle.X;
+            int endX = targetRectangle.Right;
+            float negativeAngleX = -this.angleX;
+            float negativeAngleY = -this.angleY;
+            Point centre = this.Center == Point.Empty ? Rectangle.Center(sourceRectangle) : this.Center;
+
+            // Scaling factors
+            float widthFactor = source.Width / (float)target.Width;
+            float heightFactor = source.Height / (float)target.Height;
+
+            Parallel.For(
+                startY,
+                endY,
+                y =>
+                {
+                    if (y >= targetY && y < targetBottom)
+                    {
+                        // Y coordinates of source points
+                        int originY = (int)((y - targetY) * heightFactor);
+
+                        for (int x = startX; x < endX; x++)
+                        {
+                            // X coordinates of source points
+                            int originX = (int)((x - startX) * widthFactor);
+
+                            // Skew at the centre point
+                            Point skewed = Point.Skew(new Point(originX, originY), centre, negativeAngleX, negativeAngleY);
+                            if (sourceRectangle.Contains(skewed.X, skewed.Y))
+                            {
+                                target[x, y] = source[skewed.X, skewed.Y];
+                            }
+                        }
+                        this.OnRowProcessed();
+                    }
+                });
+        }
+    }
+}

tests/ImageProcessorCore.Tests/Processors/Samplers/SamplerTests.cs

@@ -202,7 +202,32 @@
                     using (FileStream output = File.OpenWrite($"TestOutput/Rotate/{filename}"))
                     {
                         image.Rotate(45, this.ProgressUpdate)
-                             .BackgroundColor(Color.Pink)
+                             .Save(output);
+                    }
+
+                    Trace.WriteLine($"{watch.ElapsedMilliseconds}ms");
+                }
+            }
+        }
+
+        [Fact]
+        public void ImageShouldSkew()
+        {
+            if (!Directory.Exists("TestOutput/Skew"))
+            {
+                Directory.CreateDirectory("TestOutput/Skew");
+            }
+
+            foreach (string file in Files)
+            {
+                using (FileStream stream = File.OpenRead(file))
+                {
+                    Stopwatch watch = Stopwatch.StartNew();
+                    Image image = new Image(stream);
+                    string filename = Path.GetFileName(file);
+                    using (FileStream output = File.OpenWrite($"TestOutput/Skew/{filename}"))
+                    {
+                        image.Skew(45, 45, this.ProgressUpdate)
                              .Save(output);
                     }