moar RowInterval stuff

src/ImageSharp/Memory/RowInterval.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Memory
@@ -8,7 +10,7 @@ namespace SixLabors.ImageSharp.Memory
     /// <summary>
     /// Represents an interval of rows in a <see cref="Rectangle"/> and/or <see cref="Buffer2D{T}"/>
     /// </summary>
-    internal readonly struct RowInterval
+    internal readonly struct RowInterval : IEquatable<RowInterval>
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="RowInterval"/> struct.
@@ -36,7 +38,40 @@ namespace SixLabors.ImageSharp.Memory
         /// </summary>
         public int Height => this.Max - this.Min;
 
+
+        public static bool operator ==(RowInterval left, RowInterval right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(RowInterval left, RowInterval right)
+        {
+            return !left.Equals(right);
+        }
+
         /// <inheritdoc />
         public override string ToString() => $"RowInterval [{this.Min}->{this.Max}]";
+
+        public RowInterval Slice(int start) => new RowInterval(this.Min + start, this.Max);
+
+        public RowInterval Slice(int start, int length) => new RowInterval(this.Min + start, this.Min + start + length);
+
+        public bool Equals(RowInterval other)
+        {
+            return this.Min == other.Min && this.Max == other.Max;
+        }
+
+        public override bool Equals(object obj)
+        {
+            return !ReferenceEquals(null, obj) && obj is RowInterval other && this.Equals(other);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return (this.Min * 397) ^ this.Max;
+            }
+        }
     }
 }

src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeWorker.cs

@@ -45,6 +45,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
 
         private readonly int windowHeight;
 
+        private RowInterval currentWindow;
+
         public ResizeWorker(
             Configuration configuration,
             BufferArea<TPixel> source,
@@ -82,14 +84,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             this.tempRowBuffer = configuration.MemoryAllocator.Allocate<Vector4>(this.sourceRectangle.Width);
             this.tempColumnBuffer = configuration.MemoryAllocator.Allocate<Vector4>(destWidth);
 
-            this.CurrentMinY = 0;
-            this.CurrentMaxY = this.windowHeight;
+            this.currentWindow = new RowInterval(0, this.windowHeight);
         }
 
-        public int CurrentMaxY { get; private set; }
-
-        public int CurrentMinY { get; private set; }
-
         public void Dispose()
         {
             this.buffer.Dispose();
@@ -100,18 +97,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public Span<Vector4> GetColumnSpan(int x, int startY)
         {
-            return this.buffer.GetRowSpan(x).Slice(startY - this.CurrentMinY);
+            return this.buffer.GetRowSpan(x).Slice(startY - this.currentWindow.Min);
         }
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public Span<Vector4> GetColumnSpan(int x)
-        {
-            return this.buffer.GetRowSpan(x);
-        }
 
         public void Initialize()
         {
-            this.CalculateFirstPassValues(0, this.windowHeight);
+            this.CalculateFirstPassValues(this.currentWindow);
         }
 
         public void FillDestinationPixels(int minY, int maxY, int startY, Buffer2D<TPixel> destination)
@@ -123,14 +115,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
                 // Ensure offsets are normalized for cropping and padding.
                 ResizeKernel kernel = this.verticalKernelMap.GetKernel(y - startY);
 
-                while (kernel.StartIndex + kernel.Length > this.CurrentMaxY)
+                while (kernel.StartIndex + kernel.Length > this.currentWindow.Max)
                 {
                     this.Slide();
                 }
 
                 ref Vector4 tempRowBase = ref MemoryMarshal.GetReference(tempColSpan);
 
-                int top = kernel.StartIndex - this.CurrentMinY;
+                int top = kernel.StartIndex - this.currentWindow.Min;
 
                 for (int x = 0; x < this.destWidth; x++)
                 {
@@ -146,17 +138,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             }
         }
 
-        public void Slide()
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private Span<Vector4> GetColumnSpan(int x)
+        {
+            return this.buffer.GetRowSpan(x);
+        }
+
+        private void Slide()
         {
-            this.CurrentMinY = this.CurrentMinY + this.windowBandDiameter;
-            this.CurrentMaxY = Math.Min(this.CurrentMaxY + this.windowBandDiameter, this.sourceRectangle.Height);
-            this.CalculateFirstPassValues(this.CurrentMinY, this.CurrentMaxY);
+            int minY = this.currentWindow.Min + this.windowBandDiameter;
+            int maxY = Math.Min(this.currentWindow.Max + this.windowBandDiameter, this.sourceRectangle.Height);
+            this.currentWindow = new RowInterval(minY, maxY);
+            this.CalculateFirstPassValues(this.currentWindow);
         }
 
-        private void CalculateFirstPassValues(int minY, int maxY)
+        private void CalculateFirstPassValues(RowInterval window)
         {
             Span<Vector4> tempRowSpan = this.tempRowBuffer.GetSpan();
-            for (int y = minY; y < maxY; y++)
+            for (int y = window.Min; y < window.Max; y++)
             {
                 Span<TPixel> sourceRow = this.source.GetRowSpan(y);
 
@@ -167,7 +166,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
                     this.conversionModifiers);
 
                 // ref Vector4 firstPassBaseRef = ref this.buffer.Span[y - top];
-                Span<Vector4> firstPassSpan = this.buffer.Span.Slice(y - minY);
+                Span<Vector4> firstPassSpan = this.buffer.Span.Slice(y - window.Min);
 
                 for (int x = this.destWorkingRect.Left; x < this.destWorkingRect.Right; x++)
                 {

tests/ImageSharp.Tests/Helpers/RowIntervalTests.cs

@@ -34,5 +34,54 @@ namespace SixLabors.ImageSharp.Tests.Helpers
                 Assert.True(Unsafe.AreSame(ref expected0, ref actual0));
             }
         }
+
+        [Fact]
+        public void Slice1()
+        {
+            RowInterval rowInterval = new RowInterval(10, 20);
+            RowInterval sliced = rowInterval.Slice(5);
+            
+            Assert.Equal(15, sliced.Min);
+            Assert.Equal(20, sliced.Max);
+        }
+
+        [Fact]
+        public void Slice2()
+        {
+            RowInterval rowInterval = new RowInterval(10, 20);
+            RowInterval sliced = rowInterval.Slice(3, 5);
+            
+            Assert.Equal(13, sliced.Min);
+            Assert.Equal(18, sliced.Max);
+        }
+
+        [Fact]
+        public void Equality_WhenTrue()
+        {
+            RowInterval a = new RowInterval(42, 123);
+            RowInterval b = new RowInterval(42, 123);
+            
+            Assert.True(a.Equals(b));
+            Assert.True(a.Equals((object)b));
+            Assert.True(a == b);
+            Assert.Equal(a.GetHashCode(), b.GetHashCode());
+        }
+
+        [Fact]
+        public void Equality_WhenFalse()
+        {
+            RowInterval a = new RowInterval(42, 123);
+            RowInterval b = new RowInterval(42, 125);
+            RowInterval c = new RowInterval(40, 123);
+            
+            Assert.False(a.Equals(b));
+            Assert.False(c.Equals(a));
+            Assert.False(b.Equals(c));
+            
+            Assert.False(a.Equals((object)b));
+            Assert.False(a.Equals(null));
+            Assert.False(a == b);
+            Assert.True(a != c);
+        }
     }
 }