Make AffineTransformProcessor and AffineTransformBuilder API more flexible

src/ImageSharp/Processing/AffineTransformBuilder.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Collections.Generic;
 using System.Numerics;
 using SixLabors.ImageSharp.Processing.Processors.Transforms;
@@ -13,34 +14,7 @@ namespace SixLabors.ImageSharp.Processing
     /// </summary>
     public class AffineTransformBuilder
     {
-        private readonly List<Matrix3x2> matrices = new List<Matrix3x2>();
-        private readonly Rectangle sourceRectangle;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="AffineTransformBuilder"/> class.
-        /// </summary>
-        /// <param name="sourceSize">The source image size.</param>
-        public AffineTransformBuilder(Size sourceSize)
-            : this(new Rectangle(Point.Empty, sourceSize))
-        {
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="AffineTransformBuilder"/> class.
-        /// </summary>
-        /// <param name="sourceRectangle">The source rectangle.</param>
-        public AffineTransformBuilder(Rectangle sourceRectangle)
-        {
-            Guard.MustBeGreaterThan(sourceRectangle.Width, 0, nameof(sourceRectangle));
-            Guard.MustBeGreaterThan(sourceRectangle.Height, 0, nameof(sourceRectangle));
-
-            this.sourceRectangle = sourceRectangle;
-        }
-
-        /// <summary>
-        /// Gets the source image size.
-        /// </summary>
-        internal Size Size => this.sourceRectangle.Size;
+        private readonly List<Func<Size, Matrix3x2>> matrixFactories = new List<Func<Size, Matrix3x2>>();
 
         /// <summary>
         /// Prepends a centered rotation matrix using the given rotation in radians.
@@ -48,7 +22,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="radians">The amount of rotation, in radians.</param>
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder PrependCenteredRotationRadians(float radians)
-            => this.PrependMatrix(TransformUtils.CreateRotationMatrixRadians(radians, this.Size));
+            => this.Prepend(size => TransformUtils.CreateRotationMatrixRadians(radians, size));
 
         /// <summary>
         /// Appends a centered rotation matrix using the given rotation in radians.
@@ -56,7 +30,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="radians">The amount of rotation, in radians.</param>
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder AppendCenteredRotationRadians(float radians)
-            => this.AppendMatrix(TransformUtils.CreateRotationMatrixRadians(radians, this.Size));
+            => this.Append(size => TransformUtils.CreateRotationMatrixRadians(radians, size));
 
         /// <summary>
         /// Prepends a centered rotation matrix using the given rotation in degrees.
@@ -129,7 +103,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="degreesY">The Y angle, in degrees.</param>
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder PrependSkewDegrees(float degreesX, float degreesY)
-            => this.PrependMatrix(TransformUtils.CreateSkewMatrixDegrees(degreesX, degreesY, this.Size));
+            => this.Prepend(size => TransformUtils.CreateSkewMatrixDegrees(degreesX, degreesY, size));
 
         /// <summary>
         /// Appends a centered skew matrix from the give angles in degrees.
@@ -138,7 +112,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="degreesY">The Y angle, in degrees.</param>
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder AppendSkewDegrees(float degreesX, float degreesY)
-            => this.AppendMatrix(TransformUtils.CreateSkewMatrixDegrees(degreesX, degreesY, this.Size));
+            => this.Append(size => TransformUtils.CreateSkewMatrixDegrees(degreesX, degreesY, size));
 
         /// <summary>
         /// Prepends a translation matrix from the given vector.
@@ -179,7 +153,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder PrependMatrix(Matrix3x2 matrix)
         {
-            this.matrices.Insert(0, matrix);
+            this.matrixFactories.Insert(0, _ => matrix);
             return this;
         }
 
@@ -190,35 +164,50 @@ namespace SixLabors.ImageSharp.Processing
         /// <returns>The <see cref="AffineTransformBuilder"/>.</returns>
         public AffineTransformBuilder AppendMatrix(Matrix3x2 matrix)
         {
-            this.matrices.Add(matrix);
+            this.matrixFactories.Add(_ => matrix);
             return this;
         }
 
         /// <summary>
-        /// Returns the combined matrix.
+        /// Returns the combined matrix for a given source size.
+        /// </summary>
+        /// <param name="sourceSize">The source image size</param>
+        /// <returns>The <see cref="Matrix3x2"/>.</returns>
+        public Matrix3x2 BuildMatrix(Size sourceSize) => this.BuildMatrix(new Rectangle(Point.Empty, sourceSize));
+
+        /// <summary>
+        /// Returns the combined matrix for a given source rectangle.
         /// </summary>
+        /// <param name="sourceRectangle">The rectangle in the source image</param>
         /// <returns>The <see cref="Matrix3x2"/>.</returns>
-        public Matrix3x2 BuildMatrix()
+        public Matrix3x2 BuildMatrix(Rectangle sourceRectangle)
         {
-            Matrix3x2 matrix = Matrix3x2.Identity;
+            Guard.MustBeGreaterThan(sourceRectangle.Width, 0, nameof(sourceRectangle));
+            Guard.MustBeGreaterThan(sourceRectangle.Height, 0, nameof(sourceRectangle));
 
             // Translate the origin matrix to cater for source rectangle offsets.
-            if (!this.sourceRectangle.Equals(default))
-            {
-                matrix *= Matrix3x2.CreateTranslation(-this.sourceRectangle.Location);
-            }
+            var matrix = Matrix3x2.CreateTranslation(-sourceRectangle.Location);
 
-            foreach (Matrix3x2 m in this.matrices)
+            Size size = sourceRectangle.Size;
+
+            foreach (Func<Size, Matrix3x2> factory in this.matrixFactories)
             {
-                matrix *= m;
+                matrix *= factory(size);
             }
 
             return matrix;
         }
 
-        /// <summary>
-        /// Removes all matrices from the builder.
-        /// </summary>
-        public void Clear() => this.matrices.Clear();
+        private AffineTransformBuilder Prepend(Func<Size, Matrix3x2> factory)
+        {
+            this.matrixFactories.Insert(0, factory);
+            return this;
+        }
+
+        private AffineTransformBuilder Append(Func<Size, Matrix3x2> factory)
+        {
+            this.matrixFactories.Add(factory);
+            return this;
+        }
     }
 }

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

@@ -24,13 +24,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
         /// </summary>
         /// <param name="matrix">The transform matrix.</param>
         /// <param name="sampler">The sampler to perform the transform operation.</param>
-        /// <param name="sourceSize">The source image size.</param>
-        public AffineTransformProcessor(Matrix3x2 matrix, IResampler sampler, Size sourceSize)
+        /// <param name="targetDimensions">The target dimensions.</param>
+        public AffineTransformProcessor(Matrix3x2 matrix, IResampler sampler, Size targetDimensions)
         {
             Guard.NotNull(sampler, nameof(sampler));
             this.Sampler = sampler;
             this.TransformMatrix = matrix;
-            this.TargetDimensions = TransformUtils.GetTransformedSize(sourceSize, matrix);
+            this.TargetDimensions = targetDimensions;;
         }
 
         /// <summary>

src/ImageSharp/Processing/TransformExtensions.cs

@@ -1,8 +1,11 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System.Numerics;
+
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing.Processors.Transforms;
+using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Processing
 {
@@ -11,6 +14,29 @@ namespace SixLabors.ImageSharp.Processing
     /// </summary>
     public static class TransformExtensions
     {
+        /// <summary>
+        /// Performs an affine transform of an image using the specified sampling algorithm.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="ctx">The <see cref="IImageProcessingContext{TPixel}"/>.</param>
+        /// <param name="sourceRectangle">The source rectangle</param>
+        /// <param name="transform">The transformation matrix.</param>
+        /// <param name="targetDimensions">The size of the result image.</param>
+        /// <param name="sampler">The <see cref="IResampler"/> to perform the resampling.</param>
+        /// <returns>The <see cref="Image{TPixel}"/></returns>
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> ctx,
+            Rectangle sourceRectangle,
+            Matrix3x2 transform,
+            Size targetDimensions,
+            IResampler sampler)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return ctx.ApplyProcessor(
+                new AffineTransformProcessor<TPixel>(transform, sampler, targetDimensions),
+                sourceRectangle);
+        }
+
         /// <summary>
         /// Performs an affine transform of an image.
         /// </summary>
@@ -18,7 +44,9 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="source">The image to transform.</param>
         /// <param name="builder">The affine transform builder.</param>
         /// <returns>The <see cref="Image{TPixel}"/></returns>
-        public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, AffineTransformBuilder builder)
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> source,
+            AffineTransformBuilder builder)
             where TPixel : struct, IPixel<TPixel>
             => Transform(source, builder, KnownResamplers.Bicubic);
 
@@ -26,13 +54,39 @@ namespace SixLabors.ImageSharp.Processing
         /// Performs an affine transform of an image using the specified sampling algorithm.
         /// </summary>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
-        /// <param name="source">The image to transform.</param>
+        /// <param name="ctx">The <see cref="IImageProcessingContext{TPixel}"/>.</param>
+        /// <param name="sourceRectangle">The source rectangle</param>
+        /// <param name="builder">The affine transform builder.</param>
+        /// <param name="sampler">The <see cref="IResampler"/> to perform the resampling.</param>
+        /// <returns>The <see cref="Image{TPixel}"/></returns>
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> ctx,
+            Rectangle sourceRectangle,
+            AffineTransformBuilder builder,
+            IResampler sampler)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            Matrix3x2 transform = builder.BuildMatrix(sourceRectangle);
+            Size targetDimensions = TransformUtils.GetTransformedSize(sourceRectangle.Size, transform);
+            return ctx.Transform(sourceRectangle, transform, targetDimensions, sampler);
+        }
+
+        /// <summary>
+        /// Performs an affine transform of an image using the specified sampling algorithm.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="ctx">The <see cref="IImageProcessingContext{TPixel}"/>.</param>
         /// <param name="builder">The affine transform builder.</param>
         /// <param name="sampler">The <see cref="IResampler"/> to perform the resampling.</param>
         /// <returns>The <see cref="Image{TPixel}"/></returns>
-        public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, AffineTransformBuilder builder, IResampler sampler)
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> ctx,
+            AffineTransformBuilder builder,
+            IResampler sampler)
             where TPixel : struct, IPixel<TPixel>
-            => source.ApplyProcessor(new AffineTransformProcessor<TPixel>(builder.BuildMatrix(), sampler, builder.Size));
+        {
+            return ctx.Transform(new Rectangle(Point.Empty, ctx.GetCurrentSize()), builder, sampler);
+        }
 
         /// <summary>
         /// Performs a projective transform of an image.
@@ -41,7 +95,9 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="source">The image to transform.</param>
         /// <param name="builder">The affine transform builder.</param>
         /// <returns>The <see cref="Image{TPixel}"/></returns>
-        public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, ProjectiveTransformBuilder builder)
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> source,
+            ProjectiveTransformBuilder builder)
             where TPixel : struct, IPixel<TPixel>
             => Transform(source, builder, KnownResamplers.Bicubic);
 
@@ -53,7 +109,10 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="builder">The projective transform builder.</param>
         /// <param name="sampler">The <see cref="IResampler"/> to perform the resampling.</param>
         /// <returns>The <see cref="Image{TPixel}"/></returns>
-        public static IImageProcessingContext<TPixel> Transform<TPixel>(this IImageProcessingContext<TPixel> source, ProjectiveTransformBuilder builder, IResampler sampler)
+        public static IImageProcessingContext<TPixel> Transform<TPixel>(
+            this IImageProcessingContext<TPixel> source,
+            ProjectiveTransformBuilder builder,
+            IResampler sampler)
             where TPixel : struct, IPixel<TPixel>
             => source.ApplyProcessor(new ProjectiveTransformProcessor<TPixel>(builder.BuildMatrix(), sampler, builder.Size));
     }

tests/ImageSharp.Tests/Drawing/DrawImageTest.cs

@@ -73,7 +73,7 @@ namespace SixLabors.ImageSharp.Tests
             using (Image<TPixel> image = provider.GetImage())
             using (var blend = Image.Load<TPixel>(TestFile.Create(TestImages.Bmp.Car).Bytes))
             {
-                AffineTransformBuilder builder = new AffineTransformBuilder(blend.Size())
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendCenteredRotationDegrees(45F)
                     .AppendScale(new SizeF(.25F, .25F))
                     .AppendTranslation(new PointF(10, 10));

tests/ImageSharp.Tests/Processing/Transforms/AffineTransformBuilderTests.cs

@@ -12,30 +12,6 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
 {
     public class AffineTransformBuilderTests : TransformBuilderTestBase<AffineTransformBuilder>
     {
-        [Fact]
-        public void ConstructorAssignsProperties()
-        {
-            var s = new Size(1, 1);
-            var builder = new AffineTransformBuilder(new Rectangle(Point.Empty, s));
-            Assert.Equal(s, builder.Size);
-        }
-
-        [Fact]
-        public void ConstructorThrowsInvalid()
-        {
-            Assert.Throws<ArgumentOutOfRangeException>(() =>
-                {
-                    var s = new Size(0, 1);
-                    var builder = new AffineTransformBuilder(new Rectangle(Point.Empty, s));
-                });
-
-            Assert.Throws<ArgumentOutOfRangeException>(() =>
-                {
-                    var s = new Size(1, 0);
-                    var builder = new AffineTransformBuilder(new Rectangle(Point.Empty, s));
-                });
-        }
-
         protected override void AppendTranslation(AffineTransformBuilder builder, PointF translate) => builder.AppendTranslation(translate);
         protected override void AppendScale(AffineTransformBuilder builder, SizeF scale) => builder.AppendScale(scale);
         protected override void AppendRotationRadians(AffineTransformBuilder builder, float radians) => builder.AppendCenteredRotationRadians(radians);
@@ -44,12 +20,14 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
         protected override void PrependScale(AffineTransformBuilder builder, SizeF scale) => builder.PrependScale(scale);
         protected override void PrependRotationRadians(AffineTransformBuilder builder, float radians) => builder.PrependCenteredRotationRadians(radians);
 
+        protected override AffineTransformBuilder CreateBuilder(Rectangle rectangle) => new AffineTransformBuilder();
+
         protected override Vector2 Execute(
             AffineTransformBuilder builder,
             Rectangle rectangle,
             Vector2 sourcePoint)
         {
-            Matrix3x2 matrix = builder.BuildMatrix();
+            Matrix3x2 matrix = builder.BuildMatrix(rectangle);
             return Vector2.Transform(sourcePoint, matrix);
         }
     }

tests/ImageSharp.Tests/Processing/Transforms/AffineTransformTests.cs

@@ -79,7 +79,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             IResampler resampler = GetResampler(resamplerName);
             using (Image<TPixel> image = provider.GetImage())
             {
-                AffineTransformBuilder builder = new AffineTransformBuilder(image.Size())
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendCenteredRotationDegrees(30);
 
                 image.Mutate(c => c.Transform(builder, resampler));
@@ -101,12 +101,12 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.DebugSave(provider, $"_original");
-                AffineTransformBuilder builder = new AffineTransformBuilder(image.Size())
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendCenteredRotationDegrees(angleDeg)
                     .AppendScale(new SizeF(sx, sy))
                     .AppendTranslation(new PointF(tx, ty));
 
-                this.PrintMatrix(builder.BuildMatrix());
+                this.PrintMatrix(builder.BuildMatrix(image.Size()));
 
                 image.Mutate(i => i.Transform(builder, KnownResamplers.Bicubic));
 
@@ -123,7 +123,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
         {
             using (Image<TPixel> image = provider.GetImage())
             {
-                AffineTransformBuilder builder = new AffineTransformBuilder(image.Size())
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendCenteredRotationDegrees(angleDeg)
                     .AppendScale(new SizeF(s, s));
 
@@ -159,10 +159,10 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.DebugSave(provider, $"_original");
-                AffineTransformBuilder builder = new AffineTransformBuilder(rectangle)
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendScale(new SizeF(2, 1.5F));
 
-                image.Mutate(i => i.Transform(builder, KnownResamplers.Spline));
+                image.Mutate(i => i.Transform(rectangle, builder, KnownResamplers.Spline));
 
                 image.DebugSave(provider);
                 image.CompareToReferenceOutput(ValidatorComparer, provider);
@@ -178,10 +178,10 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
 
             using (Image<TPixel> image = provider.GetImage())
             {
-                AffineTransformBuilder builder = new AffineTransformBuilder(rectangle)
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendScale(new SizeF(1F, 2F));
 
-                image.Mutate(i => i.Transform(builder, KnownResamplers.Spline));
+                image.Mutate(i => i.Transform(rectangle, builder, KnownResamplers.Spline));
 
                 image.DebugSave(provider);
                 image.CompareToReferenceOutput(ValidatorComparer, provider);
@@ -196,7 +196,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             IResampler sampler = GetResampler(resamplerName);
             using (Image<TPixel> image = provider.GetImage())
             {
-                AffineTransformBuilder builder = new AffineTransformBuilder(image.Size())
+                AffineTransformBuilder builder = new AffineTransformBuilder()
                     .AppendCenteredRotationDegrees(50)
                     .AppendScale(new SizeF(.6F, .6F));
 

tests/ImageSharp.Tests/Processing/Transforms/ProjectiveTransformBuilderTests.cs

@@ -35,6 +35,8 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             });
         }
 
+        protected override ProjectiveTransformBuilder CreateBuilder(Rectangle rectangle) => new ProjectiveTransformBuilder(rectangle);
+
         protected override void AppendTranslation(ProjectiveTransformBuilder builder, PointF translate) => builder.AppendTranslation(translate);
         protected override void AppendScale(ProjectiveTransformBuilder builder, SizeF scale) => builder.AppendScale(scale);
         protected override void AppendRotationRadians(ProjectiveTransformBuilder builder, float radians) => builder.AppendCenteredRotationRadians(radians);

tests/ImageSharp.Tests/Processing/Transforms/TransformBuilderTestBase.cs

@@ -129,9 +129,25 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             Assert.Equal(p1, p2, Comparer);
         }
 
+        [Theory]
+        [InlineData(0, 1)]
+        [InlineData(1, 0)]
+        [InlineData(-1, 0)]
+        public void ThrowsForInvalidSizes(int width, int height)
+        {
+            var size = new Size(width, height);
+
+            Assert.ThrowsAny<ArgumentOutOfRangeException>(
+                () =>
+                    {
+                        TBuilder builder = this.CreateBuilder(size);
+                        this.Execute(builder, new Rectangle(Point.Empty, size), Vector2.Zero);
+                    });
+        }
+
         protected TBuilder CreateBuilder(Size size) => this.CreateBuilder(new Rectangle(Point.Empty, size));
 
-        protected virtual TBuilder CreateBuilder(Rectangle rectangle) => (TBuilder)Activator.CreateInstance(typeof(TBuilder), rectangle);
+        protected abstract TBuilder CreateBuilder(Rectangle rectangle);
 
         protected abstract void AppendTranslation(TBuilder builder, PointF translate);
         protected abstract void AppendScale(TBuilder builder, SizeF scale);