Refactor transforms to allow freeform + rectangle

src/ImageSharp/Processing/Processors/Transforms/AffineProcessor.cs

@@ -10,6 +10,7 @@ using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Helpers;
 using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.MetaData.Profiles.Exif;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Primitives;
 
@@ -23,32 +24,53 @@ namespace SixLabors.ImageSharp.Processing.Processors
         where TPixel : struct, IPixel<TPixel>
     {
         private Rectangle targetRectangle;
-        private Matrix3x2 transformMatrix;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="AffineProcessor{TPixel}"/> class.
         /// </summary>
+        /// <param name="matrix">The transform matrix</param>
         /// <param name="sampler">The sampler to perform the transform operation.</param>
-        protected AffineProcessor(IResampler sampler)
+        protected AffineProcessor(Matrix3x2 matrix, IResampler sampler)
+           : this(matrix, sampler, Rectangle.Empty)
         {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AffineProcessor{TPixel}"/> class.
+        /// </summary>
+        /// <param name="matrix">The transform matrix</param>
+        /// <param name="sampler">The sampler to perform the transform operation.</param>
+        /// <param name="rectangle">The rectangle to constrain the transformed image to.</param>
+        protected AffineProcessor(Matrix3x2 matrix, IResampler sampler, Rectangle rectangle)
+        {
+            // Tansforms are inverted else the output is the opposite of the expected.
+            Matrix3x2.Invert(matrix, out matrix);
+            this.TransformMatrix = matrix;
+
             this.Sampler = sampler;
+
+            this.targetRectangle = rectangle;
         }
 
         /// <summary>
-        /// Gets the sampler to perform interpolation of the transform operation.
+        /// Gets the matrix used to supply the affine transform
         /// </summary>
-        public IResampler Sampler { get; }
+        public Matrix3x2 TransformMatrix { get; }
 
         /// <summary>
-        /// Returns the processing matrix used for transforming the image.
+        /// Gets the sampler to perform interpolation of the transform operation.
         /// </summary>
-        /// <returns>The <see cref="Matrix3x2"/></returns>
-        protected abstract Matrix3x2 GetTransformMatrix();
+        public IResampler Sampler { get; }
 
         /// <inheritdoc/>
         protected override Image<TPixel> CreateDestination(Image<TPixel> source, Rectangle sourceRectangle)
         {
-            this.ResizeCanvas(sourceRectangle);
+            if (this.targetRectangle == Rectangle.Empty)
+            {
+                this.targetRectangle = Matrix3x2.Invert(this.TransformMatrix, out Matrix3x2 sizeMatrix)
+                                           ? ImageMaths.GetBoundingRectangle(sourceRectangle, sizeMatrix)
+                                           : sourceRectangle;
+            }
 
             // We will always be creating the clone even for mutate because we may need to resize the canvas
             IEnumerable<ImageFrame<TPixel>> frames =
@@ -66,7 +88,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
             Rectangle sourceBounds = source.Bounds();
 
             // Since could potentially be resizing the canvas we need to re-center the matrix
-            Matrix3x2 matrix = this.GetCenteredMatrix(source);
+            Matrix3x2 matrix = this.GetProcessingMatrix(sourceBounds, this.targetRectangle);
 
             if (this.Sampler is NearestNeighborResampler)
             {
@@ -188,18 +210,37 @@ namespace SixLabors.ImageSharp.Processing.Processors
             }
         }
 
+        /// <inheritdoc/>
+        protected override void AfterImageApply(Image<TPixel> source, Image<TPixel> destination, Rectangle sourceRectangle)
+        {
+            ExifProfile profile = destination.MetaData.ExifProfile;
+            if (profile == null)
+            {
+                return;
+            }
+
+            if (profile.GetValue(ExifTag.PixelXDimension) != null)
+            {
+                profile.SetValue(ExifTag.PixelXDimension, destination.Width);
+            }
+
+            if (profile.GetValue(ExifTag.PixelYDimension) != null)
+            {
+                profile.SetValue(ExifTag.PixelYDimension, destination.Height);
+            }
+        }
+
         /// <summary>
-        /// Gets a transform matrix adjusted to center upon the target image bounds.
+        /// Gets a transform matrix adjusted for final processing based upon the target image bounds.
         /// </summary>
-        /// <param name="source">The source image.</param>
+        /// <param name="sourceRectangle">The source image bounds.</param>
+        /// <param name="destinationRectangle">The destination image bounds.</param>
         /// <returns>
         /// The <see cref="Matrix3x2"/>.
         /// </returns>
-        protected Matrix3x2 GetCenteredMatrix(ImageFrame<TPixel> source)
+        protected virtual Matrix3x2 GetProcessingMatrix(Rectangle sourceRectangle, Rectangle destinationRectangle)
         {
-            var translationToTargetCenter = Matrix3x2.CreateTranslation(-this.targetRectangle.Width * .5F, -this.targetRectangle.Height * .5F);
-            var translateToSourceCenter = Matrix3x2.CreateTranslation(source.Width * .5F, source.Height * .5F);
-            return translationToTargetCenter * this.transformMatrix * translateToSourceCenter;
+            return this.TransformMatrix;
         }
 
         /// <summary>
@@ -269,19 +310,6 @@ namespace SixLabors.ImageSharp.Processing.Processors
             }
         }
 
-        /// <summary>
-        /// Creates a new target canvas to contain the results of the matrix transform.
-        /// </summary>
-        /// <param name="sourceRectangle">The source rectangle.</param>
-        private void ResizeCanvas(Rectangle sourceRectangle)
-        {
-            this.transformMatrix = this.GetTransformMatrix();
-
-            this.targetRectangle = Matrix3x2.Invert(this.transformMatrix, out Matrix3x2 sizeMatrix)
-                                     ? ImageMaths.GetBoundingRectangle(sourceRectangle, sizeMatrix)
-                                     : sourceRectangle;
-        }
-
         /// <summary>
         /// Calculates the sampling radius for the current sampler
         /// </summary>

src/ImageSharp/Processing/Processors/Transforms/CenteredAffineProcessor.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Numerics;
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.Primitives;
+
+namespace SixLabors.ImageSharp.Processing.Processors
+{
+    internal abstract class CenteredAffineProcessor<TPixel> : AffineProcessor<TPixel>
+        where TPixel : struct, IPixel<TPixel>
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CenteredAffineProcessor{TPixel}"/> class.
+        /// </summary>
+        /// <param name="matrix">The transform matrix</param>
+        /// <param name="sampler">The sampler to perform the transform operation.</param>
+        protected CenteredAffineProcessor(Matrix3x2 matrix, IResampler sampler)
+            : base(matrix, sampler)
+        {
+        }
+
+        /// <inheritdoc/>
+        protected override Matrix3x2 GetProcessingMatrix(Rectangle sourceRectangle, Rectangle destinationRectangle)
+        {
+            var translationToTargetCenter = Matrix3x2.CreateTranslation(-destinationRectangle.Width * .5F, -destinationRectangle.Height * .5F);
+            var translateToSourceCenter = Matrix3x2.CreateTranslation(sourceRectangle.Width * .5F, sourceRectangle.Height * .5F);
+            return translationToTargetCenter * this.TransformMatrix * translateToSourceCenter;
+        }
+    }
+}

src/ImageSharp/Processing/Processors/Transforms/RotateProcessor.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Helpers;
@@ -16,15 +15,15 @@ namespace SixLabors.ImageSharp.Processing.Processors
     /// Provides methods that allow the rotating of images.
     /// </summary>
     /// <typeparam name="TPixel">The pixel format.</typeparam>
-    internal class RotateProcessor<TPixel> : AffineProcessor<TPixel>
+    internal class RotateProcessor<TPixel> : CenteredAffineProcessor<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="RotateProcessor{TPixel}"/> class.
         /// </summary>
-        /// <param name="angle">The angle of rotation in degrees.</param>
-        public RotateProcessor(float angle)
-            : this(angle, KnownResamplers.NearestNeighbor)
+        /// <param name="degrees">The angle of rotation in degrees.</param>
+        public RotateProcessor(float degrees)
+            : this(degrees, KnownResamplers.NearestNeighbor)
         {
         }
 
@@ -34,7 +33,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// <param name="degrees">The angle of rotation in degrees.</param>
         /// <param name="sampler">The sampler to perform the rotating operation.</param>
         public RotateProcessor(float degrees, IResampler sampler)
-            : base(sampler)
+            : base(Matrix3x2Extensions.CreateRotationDegrees(degrees, PointF.Empty), sampler)
         {
             this.Degrees = degrees;
         }
@@ -44,15 +43,6 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// </summary>
         public float Degrees { get; }
 
-        /// <inheritdoc/>
-        protected override Matrix3x2 GetTransformMatrix()
-        {
-            // Tansforms are inverted else the output is the opposite of the expected.
-            Matrix3x2 matrix = Matrix3x2Extensions.CreateRotationDegrees(this.Degrees, PointF.Empty);
-            Matrix3x2.Invert(matrix, out matrix);
-            return matrix;
-        }
-
         /// <inheritdoc/>
         protected override void OnApply(ImageFrame<TPixel> source, ImageFrame<TPixel> destination, Rectangle sourceRectangle, Configuration configuration)
         {
@@ -73,7 +63,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
                 return;
             }
 
-            if (MathF.Abs(this.Degrees) < Constants.Epsilon)
+            if (MathF.Abs(WrapDegrees(this.Degrees)) < Constants.Epsilon)
             {
                 // No need to do anything so return.
                 return;
@@ -81,11 +71,24 @@ namespace SixLabors.ImageSharp.Processing.Processors
 
             profile.RemoveValue(ExifTag.Orientation);
 
-            if (profile.GetValue(ExifTag.PixelXDimension) != null)
+            base.AfterImageApply(source, destination, sourceRectangle);
+        }
+
+        /// <summary>
+        /// Wraps a given angle in degrees so that it falls withing the 0-360 degree range
+        /// </summary>
+        /// <param name="degrees">The angle of rotation in degrees.</param>
+        /// <returns>The <see cref="float"/></returns>
+        private static float WrapDegrees(float degrees)
+        {
+            degrees = degrees % 360;
+
+            if (degrees < 0)
             {
-                profile.SetValue(ExifTag.PixelXDimension, source.Width);
-                profile.SetValue(ExifTag.PixelYDimension, source.Height);
+                degrees += 360;
             }
+
+            return degrees;
         }
 
         /// <summary>
@@ -99,26 +102,29 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// </returns>
         private bool OptimizedApply(ImageFrame<TPixel> source, ImageFrame<TPixel> destination, Configuration configuration)
         {
-            if (MathF.Abs(this.Degrees) < Constants.Epsilon)
+            // Wrap the degrees to keep within 0-360 so we can apply optimizations when possible.
+            float degrees = WrapDegrees(this.Degrees);
+
+            if (MathF.Abs(degrees) < Constants.Epsilon)
             {
                 // The destination will be blank here so copy all the pixel data over
                 source.GetPixelSpan().CopyTo(destination.GetPixelSpan());
                 return true;
             }
 
-            if (MathF.Abs(this.Degrees - 90) < Constants.Epsilon)
+            if (MathF.Abs(degrees - 90) < Constants.Epsilon)
             {
                 this.Rotate90(source, destination, configuration);
                 return true;
             }
 
-            if (MathF.Abs(this.Degrees - 180) < Constants.Epsilon)
+            if (MathF.Abs(degrees - 180) < Constants.Epsilon)
             {
                 this.Rotate180(source, destination, configuration);
                 return true;
             }
 
-            if (MathF.Abs(this.Degrees - 270) < Constants.Epsilon)
+            if (MathF.Abs(degrees - 270) < Constants.Epsilon)
             {
                 this.Rotate270(source, destination, configuration);
                 return true;

src/ImageSharp/Processing/Processors/Transforms/SkewProcessor.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System.Numerics;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Primitives;
 
@@ -11,7 +10,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
     /// Provides methods that allow the skewing of images.
     /// </summary>
     /// <typeparam name="TPixel">The pixel format.</typeparam>
-    internal class SkewProcessor<TPixel> : AffineProcessor<TPixel>
+    internal class SkewProcessor<TPixel> : CenteredAffineProcessor<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
         /// <summary>
@@ -31,7 +30,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// <param name="degreesY">The angle in degrees to perform the skew along the y-axis.</param>
         /// <param name="sampler">The sampler to perform the skew operation.</param>
         public SkewProcessor(float degreesX, float degreesY, IResampler sampler)
-            : base(sampler)
+            : base(Matrix3x2Extensions.CreateSkewDegrees(degreesX, degreesY, PointF.Empty), sampler)
         {
             this.DegreesX = degreesX;
             this.DegreesY = degreesY;
@@ -46,14 +45,5 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// Gets the angle of rotation along the y-axis in degrees.
         /// </summary>
         public float DegreesY { get; }
-
-        /// <inheritdoc/>
-        protected override Matrix3x2 GetTransformMatrix()
-        {
-            // Tansforms are inverted else the output is the opposite of the expected.
-            Matrix3x2 matrix = Matrix3x2Extensions.CreateSkewDegrees(this.DegreesX, this.DegreesY, PointF.Empty);
-            Matrix3x2.Invert(matrix, out matrix);
-            return matrix;
-        }
     }
 }

src/ImageSharp/Processing/Processors/Transforms/TransformProcessor.cs

@@ -3,6 +3,7 @@
 
 using System.Numerics;
 using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Processing.Processors
 {
@@ -28,22 +29,19 @@ namespace SixLabors.ImageSharp.Processing.Processors
         /// <param name="matrix">The transformation matrix</param>
         /// <param name="sampler">The sampler to perform the transform operation.</param>
         public TransformProcessor(Matrix3x2 matrix, IResampler sampler)
-            : base(sampler)
+            : base(matrix, sampler)
         {
-            // Tansforms are inverted else the output is the opposite of the expected.
-            Matrix3x2.Invert(matrix, out matrix);
-            this.TransformMatrix = matrix;
         }
 
         /// <summary>
-        /// Gets the transform matrix
+        /// Initializes a new instance of the <see cref="TransformProcessor{TPixel}"/> class.
         /// </summary>
-        public Matrix3x2 TransformMatrix { get; }
-
-        /// <inheritdoc />
-        protected override Matrix3x2 GetTransformMatrix()
+        /// <param name="matrix">The transform matrix</param>
+        /// <param name="sampler">The sampler to perform the transform operation.</param>
+        /// <param name="rectangle">The rectangle to constrain the transformed image to.</param>
+        public TransformProcessor(Matrix3x2 matrix, IResampler sampler, Rectangle rectangle)
+            : base(matrix, sampler, rectangle)
         {
-            return this.TransformMatrix;
         }
     }
 }

src/ImageSharp/Processing/Transforms/Transform.cs

@@ -5,6 +5,7 @@ using System.Numerics;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
 using SixLabors.ImageSharp.Processing.Processors;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp
 {
@@ -34,6 +35,19 @@ namespace SixLabors.ImageSharp
         /// <returns>The <see cref="Image{TPixel}"/></returns>
         public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, Matrix3x2 matrix, IResampler sampler)
             where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new TransformProcessor<TPixel>(matrix, sampler));
+            => Transform(source, matrix, sampler, Rectangle.Empty);
+
+        /// <summary>
+        /// Transforms an image by the given matrix using the specified sampling algorithm.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="source">The image to skew.</param>
+        /// <param name="matrix">The transformation matrix.</param>
+        /// <param name="sampler">The <see cref="IResampler"/> to perform the resampling.</param>
+        /// <param name="rectangle">The rectangle to constrain the transformed image to.</param>
+        /// <returns>The <see cref="Image{TPixel}"/></returns>
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, Matrix3x2 matrix, IResampler sampler, Rectangle rectangle)
+            where TPixel : struct, IPixel<TPixel>
+            => source.ApplyProcessor(new TransformProcessor<TPixel>(matrix, sampler, rectangle));
     }
 }