use abstract base class instead of interface

src/ImageSharp.Drawing/Brushes/IBrush.cs

@@ -14,7 +14,7 @@ namespace ImageSharp.Drawing
     /// </summary>
     /// <typeparam name="TColor">The pixel format.</typeparam>
     /// <remarks>
-    /// A brush is a simple class that will return an <see cref="IBrushApplicator{TColor}" /> that will perform the
+    /// A brush is a simple class that will return an <see cref="BrushApplicator{TColor}" /> that will perform the
     /// logic for converting a pixel location to a <typeparamref name="TColor"/>.
     /// </remarks>
     public interface IBrush<TColor>
@@ -32,6 +32,6 @@ namespace ImageSharp.Drawing
         /// The <paramref name="region" /> when being applied to things like shapes would usually be the
         /// bounding box of the shape not necessarily the bounds of the whole image
         /// </remarks>
-        IBrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> pixelSource, RectangleF region);
+        BrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> pixelSource, RectangleF region);
     }
 }

src/ImageSharp.Drawing/Brushes/ImageBrush{TColor}.cs

@@ -32,7 +32,7 @@ namespace ImageSharp.Drawing.Brushes
         }
 
         /// <inheritdoc />
-        public IBrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
+        public BrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
         {
             return new ImageBrushApplicator(this.image, region);
         }
@@ -40,7 +40,7 @@ namespace ImageSharp.Drawing.Brushes
         /// <summary>
         /// The image brush applicator.
         /// </summary>
-        private class ImageBrushApplicator : IBrushApplicator<TColor>
+        private class ImageBrushApplicator : BrushApplicator<TColor>
         {
             /// <summary>
             /// The source pixel accessor.
@@ -86,7 +86,7 @@ namespace ImageSharp.Drawing.Brushes
             /// <returns>
             /// The color
             /// </returns>
-            public TColor GetColor(Vector2 point)
+            public override TColor GetColor(Vector2 point)
             {
                 // Offset the requested pixel by the value in the rectangle (the shapes position)
                 point = point - this.offset;
@@ -97,7 +97,7 @@ namespace ImageSharp.Drawing.Brushes
             }
 
             /// <inheritdoc />
-            public void Dispose()
+            public override void Dispose()
             {
                 this.source.Dispose();
             }

src/ImageSharp.Drawing/Brushes/PatternBrush{TColor}.cs

@@ -95,7 +95,7 @@ namespace ImageSharp.Drawing.Brushes
         }
 
         /// <inheritdoc />
-        public IBrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
+        public BrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
         {
             return new PatternBrushApplicator(this.pattern, this.stride);
         }
@@ -103,7 +103,7 @@ namespace ImageSharp.Drawing.Brushes
         /// <summary>
         /// The pattern brush applicator.
         /// </summary>
-        private class PatternBrushApplicator : IBrushApplicator<TColor>
+        private class PatternBrushApplicator : BrushApplicator<TColor>
         {
             /// <summary>
             /// The patter x-length.
@@ -139,7 +139,7 @@ namespace ImageSharp.Drawing.Brushes
             /// <returns>
             /// The color
             /// </returns>
-            public TColor GetColor(Vector2 point)
+            public override TColor GetColor(Vector2 point)
             {
                 int x = (int)point.X % this.xLength;
                 int y = (int)point.Y % this.stride;
@@ -148,7 +148,7 @@ namespace ImageSharp.Drawing.Brushes
             }
 
             /// <inheritdoc />
-            public void Dispose()
+            public override void Dispose()
             {
                 // noop
             }

src/ImageSharp.Drawing/Brushes/Processors/IBrushApplicator.cs → src/ImageSharp.Drawing/Brushes/Processors/BrushApplicator.cs

@@ -1,4 +1,4 @@
-// <copyright file="IBrushApplicator.cs" company="James Jackson-South">
+// <copyright file="BrushApplicator.cs" company="James Jackson-South">
 // Copyright (c) James Jackson-South and contributors.
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
@@ -13,14 +13,19 @@ namespace ImageSharp.Drawing.Processors
     /// </summary>
     /// <typeparam name="TColor">The pixel format.</typeparam>
     /// <seealso cref="System.IDisposable" />
-    public interface IBrushApplicator<TColor> : IDisposable // disposable will be required if/when there is an ImageBrush
+    public abstract class BrushApplicator<TColor> : IDisposable // disposable will be required if/when there is an ImageBrush
         where TColor : struct, IPackedPixel, IEquatable<TColor>
     {
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public abstract void Dispose();
+
         /// <summary>
         /// Gets the color for a single pixel.
         /// </summary>
         /// <param name="point">The point.</param>
         /// <returns>The color</returns>
-        TColor GetColor(Vector2 point);
+        public abstract TColor GetColor(Vector2 point);
     }
 }

src/ImageSharp.Drawing/Brushes/RecolorBrush{TColor}.cs

@@ -55,7 +55,7 @@ namespace ImageSharp.Drawing.Brushes
         public TColor TargetColor { get; }
 
         /// <inheritdoc />
-        public IBrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
+        public BrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
         {
             return new RecolorBrushApplicator(sourcePixels, this.SourceColor, this.TargetColor, this.Threshold);
         }
@@ -63,7 +63,7 @@ namespace ImageSharp.Drawing.Brushes
         /// <summary>
         /// The recolor brush applicator.
         /// </summary>
-        private class RecolorBrushApplicator : IBrushApplicator<TColor>
+        private class RecolorBrushApplicator : BrushApplicator<TColor>
         {
             /// <summary>
             /// The source pixel accessor.
@@ -113,7 +113,7 @@ namespace ImageSharp.Drawing.Brushes
             /// <returns>
             /// The color
             /// </returns>
-            public TColor GetColor(Vector2 point)
+            public override TColor GetColor(Vector2 point)
             {
                 // Offset the requested pixel by the value in the rectangle (the shapes position)
                 TColor result = this.source[(int)point.X, (int)point.Y];
@@ -130,9 +130,8 @@ namespace ImageSharp.Drawing.Brushes
             }
 
             /// <inheritdoc />
-            public void Dispose()
+            public override void Dispose()
             {
-                // we didn't make the lock on the PixelAccessor we shouldn't release it.
             }
         }
     }

src/ImageSharp.Drawing/Brushes/SolidBrush{TColor}.cs

@@ -40,7 +40,7 @@ namespace ImageSharp.Drawing.Brushes
         public TColor Color => this.color;
 
         /// <inheritdoc />
-        public IBrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
+        public BrushApplicator<TColor> CreateApplicator(PixelAccessor<TColor> sourcePixels, RectangleF region)
         {
             return new SolidBrushApplicator(this.color);
         }
@@ -48,7 +48,7 @@ namespace ImageSharp.Drawing.Brushes
         /// <summary>
         /// The solid brush applicator.
         /// </summary>
-        private class SolidBrushApplicator : IBrushApplicator<TColor>
+        private class SolidBrushApplicator : BrushApplicator<TColor>
         {
             /// <summary>
             /// The solid color.
@@ -71,13 +71,13 @@ namespace ImageSharp.Drawing.Brushes
             /// <returns>
             /// The color
             /// </returns>
-            public TColor GetColor(Vector2 point)
+            public override TColor GetColor(Vector2 point)
             {
                 return this.color;
             }
 
             /// <inheritdoc />
-            public void Dispose()
+            public override void Dispose()
             {
                 // noop
             }

src/ImageSharp.Drawing/Pens/Pen{TColor}.cs

@@ -125,7 +125,7 @@ namespace ImageSharp.Drawing.Pens
 
         private class SolidPenApplicator : IPenApplicator<TColor>
         {
-            private readonly IBrushApplicator<TColor> brush;
+            private readonly BrushApplicator<TColor> brush;
             private readonly float halfWidth;
 
             public SolidPenApplicator(PixelAccessor<TColor> sourcePixels, IBrush<TColor> brush, RectangleF region, float width)
@@ -135,17 +135,17 @@ namespace ImageSharp.Drawing.Pens
                 this.RequiredRegion = RectangleF.Outset(region, width);
             }
 
-            public RectangleF RequiredRegion
+            public override RectangleF RequiredRegion
             {
                 get;
             }
 
-            public void Dispose()
+            public override void Dispose()
             {
                 this.brush.Dispose();
             }
 
-            public ColoredPointInfo<TColor> GetColor(PointInfo info)
+            public override ColoredPointInfo<TColor> GetColor(PointInfo info)
             {
                 var result = default(ColoredPointInfo<TColor>);
                 result.Color = this.brush.GetColor(info.SearchPoint);
@@ -166,7 +166,7 @@ namespace ImageSharp.Drawing.Pens
 
         private class PatternPenApplicator : IPenApplicator<TColor>
         {
-            private readonly IBrushApplicator<TColor> brush;
+            private readonly BrushApplicator<TColor> brush;
             private readonly float halfWidth;
             private readonly float[] pattern;
             private readonly float totalLength;
@@ -188,17 +188,17 @@ namespace ImageSharp.Drawing.Pens
                 this.RequiredRegion = RectangleF.Outset(region, width);
             }
 
-            public RectangleF RequiredRegion
+            public override RectangleF RequiredRegion
             {
                 get;
             }
 
-            public void Dispose()
+            public override void Dispose()
             {
                 this.brush.Dispose();
             }
 
-            public ColoredPointInfo<TColor> GetColor(PointInfo info)
+            public override ColoredPointInfo<TColor> GetColor(PointInfo info)
             {
                 var infoResult = default(ColoredPointInfo<TColor>);
                 infoResult.DistanceFromElement = float.MaxValue; // is really outside the element

src/ImageSharp.Drawing/Pens/Processors/IPenApplicator.cs

@@ -12,7 +12,7 @@ namespace ImageSharp.Drawing.Processors
     /// primitive that converts a <see cref="PointInfo"/> into a color and a distance away from the drawable part of the path.
     /// </summary>
     /// <typeparam name="TColor">The type of the color.</typeparam>
-    public interface IPenApplicator<TColor> : IDisposable
+    public abstract class IPenApplicator<TColor> : IDisposable
         where TColor : struct, IPackedPixel, IEquatable<TColor>
     {
         /// <summary>
@@ -21,13 +21,18 @@ namespace ImageSharp.Drawing.Processors
         /// <value>
         /// The required region.
         /// </value>
-        RectangleF RequiredRegion { get; }
+        public abstract RectangleF RequiredRegion { get; }
+
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public abstract void Dispose();
 
         /// <summary>
         /// Gets a <see cref="ColoredPointInfo{TColor}" /> from a point represented by a <see cref="PointInfo" />.
         /// </summary>
         /// <param name="info">The information to extract color details about.</param>
         /// <returns>Returns the color details and distance from a solid bit of the line.</returns>
-        ColoredPointInfo<TColor> GetColor(PointInfo info);
+        public abstract ColoredPointInfo<TColor> GetColor(PointInfo info);
     }
 }

src/ImageSharp.Drawing/Processors/FillProcessor.cs

@@ -62,7 +62,7 @@ namespace ImageSharp.Drawing.Processors
             // for example If brush is SolidBrush<TColor> then we could just get the color upfront
             // and skip using the IBrushApplicator<TColor>?.
             using (PixelAccessor<TColor> sourcePixels = source.Lock())
-            using (IBrushApplicator<TColor> applicator = this.brush.CreateApplicator(sourcePixels, sourceRectangle))
+            using (BrushApplicator<TColor> applicator = this.brush.CreateApplicator(sourcePixels, sourceRectangle))
             {
                 Parallel.For(
                     minY,

src/ImageSharp.Drawing/Processors/FillShapeProcessor.cs

@@ -73,7 +73,7 @@ namespace ImageSharp.Drawing.Processors
             }
 
             using (PixelAccessor<TColor> sourcePixels = source.Lock())
-            using (IBrushApplicator<TColor> applicator = this.fillColor.CreateApplicator(sourcePixels, rect))
+            using (BrushApplicator<TColor> applicator = this.fillColor.CreateApplicator(sourcePixels, rect))
             {
                 Parallel.For(
                 minY,

src/ImageSharp.Drawing/Processors/FillShapeProcessorFast.cs

@@ -67,7 +67,7 @@ namespace ImageSharp.Drawing.Processors
             int maxIntersections = this.poly.MaxIntersections;
 
             using (PixelAccessor<TColor> sourcePixels = source.Lock())
-            using (IBrushApplicator<TColor> applicator = this.fillColor.CreateApplicator(sourcePixels, rect))
+            using (BrushApplicator<TColor> applicator = this.fillColor.CreateApplicator(sourcePixels, rect))
             {
                 Parallel.For(
                 minY,