Change existing gradient brushes to accept PointF

src/ImageSharp.Drawing/Processing/EllipticGradientBrush{TPixel}.cs

@@ -18,9 +18,9 @@ namespace SixLabors.ImageSharp.Processing
     public sealed class EllipticGradientBrush<TPixel> : GradientBrushBase<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
-        private readonly Point center;
+        private readonly PointF center;
 
-        private readonly Point referenceAxisEnd;
+        private readonly PointF referenceAxisEnd;
 
         private readonly float axisRatio;
 
@@ -35,8 +35,8 @@ public sealed class EllipticGradientBrush<TPixel> : GradientBrushBase<TPixel>
         /// <param name="repetitionMode">Defines how the colors of the gradients are repeated.</param>
         /// <param name="colorStops">the color stops as defined in base class.</param>
         public EllipticGradientBrush(
-            Point center,
-            Point referenceAxisEnd,
+            PointF center,
+            PointF referenceAxisEnd,
             float axisRatio,
             GradientRepetitionMode repetitionMode,
             params ColorStop<TPixel>[] colorStops)
@@ -64,9 +64,9 @@ public override BrushApplicator<TPixel> CreateApplicator(
         /// <inheritdoc />
         private sealed class RadialGradientBrushApplicator : GradientBrushApplicatorBase
         {
-            private readonly Point center;
+            private readonly PointF center;
 
-            private readonly Point referenceAxisEnd;
+            private readonly PointF referenceAxisEnd;
 
             private readonly float axisRatio;
 
@@ -99,8 +99,8 @@ private sealed class RadialGradientBrushApplicator : GradientBrushApplicatorBase
             public RadialGradientBrushApplicator(
                 ImageFrame<TPixel> target,
                 GraphicsOptions options,
-                Point center,
-                Point referenceAxisEnd,
+                PointF center,
+                PointF referenceAxisEnd,
                 float axisRatio,
                 ColorStop<TPixel>[] colorStops,
                 GradientRepetitionMode repetitionMode)
@@ -129,7 +129,7 @@ public override void Dispose()
             }
 
             /// <inheritdoc />
-            protected override float PositionOnGradient(int xt, int yt)
+            protected override float PositionOnGradient(float xt, float yt)
             {
                 float x0 = xt - this.center.X;
                 float y0 = yt - this.center.Y;

src/ImageSharp.Drawing/Processing/GradientBrushBase{TPixel}.cs

@@ -81,7 +81,7 @@ protected GradientBrushApplicatorBase(
             {
                 get
                 {
-                    float positionOnCompleteGradient = this.PositionOnGradient(x, y);
+                    float positionOnCompleteGradient = this.PositionOnGradient(x + 0.5f, y + 0.5f);
 
                     switch (this.repetitionMode)
                     {
@@ -137,18 +137,18 @@ protected GradientBrushApplicatorBase(
             }
 
             /// <summary>
-            /// calculates the position on the gradient for a given pixel.
+            /// calculates the position on the gradient for a given point.
             /// This method is abstract as it's content depends on the shape of the gradient.
             /// </summary>
-            /// <param name="x">The x coordinate of the pixel</param>
-            /// <param name="y">The y coordinate of the pixel</param>
+            /// <param name="x">The x coordinate of the point</param>
+            /// <param name="y">The y coordinate of the point</param>
             /// <returns>
-            /// The position the given pixel has on the gradient.
+            /// The position the given point has on the gradient.
             /// The position is not bound to the [0..1] interval.
             /// Values outside of that interval may be treated differently,
             /// e.g. for the <see cref="GradientRepetitionMode" /> enum.
             /// </returns>
-            protected abstract float PositionOnGradient(int x, int y);
+            protected abstract float PositionOnGradient(float x, float y);
 
             private (ColorStop<TPixel> from, ColorStop<TPixel> to) GetGradientSegment(
                 float positionOnCompleteGradient)

src/ImageSharp.Drawing/Processing/LinearGradientBrush{TPixel}.cs

@@ -17,9 +17,9 @@ namespace SixLabors.ImageSharp.Processing
     public sealed class LinearGradientBrush<TPixel> : GradientBrushBase<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
-        private readonly Point p1;
+        private readonly PointF p1;
 
-        private readonly Point p2;
+        private readonly PointF p2;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="LinearGradientBrush{TPixel}"/> class.
@@ -29,8 +29,8 @@ public sealed class LinearGradientBrush<TPixel> : GradientBrushBase<TPixel>
         /// <param name="repetitionMode">defines how colors are repeated.</param>
         /// <param name="colorStops"><inheritdoc /></param>
         public LinearGradientBrush(
-            Point p1,
-            Point p2,
+            PointF p1,
+            PointF p2,
             GradientRepetitionMode repetitionMode,
             params ColorStop<TPixel>[] colorStops)
             : base(repetitionMode, colorStops)
@@ -48,9 +48,9 @@ public override BrushApplicator<TPixel> CreateApplicator(ImageFrame<TPixel> sour
         /// </summary>
         private sealed class LinearGradientBrushApplicator : GradientBrushApplicatorBase
         {
-            private readonly Point start;
+            private readonly PointF start;
 
-            private readonly Point end;
+            private readonly PointF end;
 
             /// <summary>
             /// the vector along the gradient, x component
@@ -93,8 +93,8 @@ private sealed class LinearGradientBrushApplicator : GradientBrushApplicatorBase
             /// <param name="options">the graphics options</param>
             public LinearGradientBrushApplicator(
                 ImageFrame<TPixel> source,
-                Point start,
-                Point end,
+                PointF start,
+                PointF end,
                 ColorStop<TPixel>[] colorStops,
                 GradientRepetitionMode repetitionMode,
                 GraphicsOptions options)
@@ -116,15 +116,15 @@ public LinearGradientBrushApplicator(
                 this.length = (float)Math.Sqrt(this.alongsSquared);
             }
 
-            protected override float PositionOnGradient(int x, int y)
+            protected override float PositionOnGradient(float x, float y)
             {
                 if (this.acrossX == 0)
                 {
-                    return (x - this.start.X) / (float)(this.end.X - this.start.X);
+                    return (x - this.start.X) / (this.end.X - this.start.X);
                 }
                 else if (this.acrossY == 0)
                 {
-                    return (y - this.start.Y) / (float)(this.end.Y - this.start.Y);
+                    return (y - this.start.Y) / (this.end.Y - this.start.Y);
                 }
                 else
                 {

src/ImageSharp.Drawing/Processing/RadialGradientBrush{TPixel}.cs

@@ -15,7 +15,7 @@ namespace SixLabors.ImageSharp.Processing
     public sealed class RadialGradientBrush<TPixel> : GradientBrushBase<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
-        private readonly Point center;
+        private readonly PointF center;
 
         private readonly float radius;
 
@@ -25,7 +25,7 @@ public sealed class RadialGradientBrush<TPixel> : GradientBrushBase<TPixel>
         /// <param name="repetitionMode">Defines how the colors in the gradient are repeated.</param>
         /// <param name="colorStops">the color stops as defined in base class.</param>
         public RadialGradientBrush(
-            Point center,
+            PointF center,
             float radius,
             GradientRepetitionMode repetitionMode,
             params ColorStop<TPixel>[] colorStops)
@@ -51,7 +51,7 @@ public override BrushApplicator<TPixel> CreateApplicator(
         /// <inheritdoc />
         private sealed class RadialGradientBrushApplicator : GradientBrushApplicatorBase
         {
-            private readonly Point center;
+            private readonly PointF center;
 
             private readonly float radius;
 
@@ -67,7 +67,7 @@ private sealed class RadialGradientBrushApplicator : GradientBrushApplicatorBase
             public RadialGradientBrushApplicator(
                 ImageFrame<TPixel> target,
                 GraphicsOptions options,
-                Point center,
+                PointF center,
                 float radius,
                 ColorStop<TPixel>[] colorStops,
                 GradientRepetitionMode repetitionMode)
@@ -89,7 +89,7 @@ public override void Dispose()
             /// <param name="x">The X coordinate of the target pixel.</param>
             /// <param name="y">The Y coordinate of the target pixel.</param>
             /// <returns>the position on the color gradient.</returns>
-            protected override float PositionOnGradient(int x, int y)
+            protected override float PositionOnGradient(float x, float y)
             {
                 float distance = (float)Math.Sqrt(Math.Pow(this.center.X - x, 2) + Math.Pow(this.center.Y - y, 2));
                 return distance / this.radius;

tests/ImageSharp.Tests/Drawing/FillLinearGradientBrushTests.cs

@@ -275,10 +275,6 @@ public void DiagonalReturnsCorrectImages<TPixel>(
                 int verticalSign = startY == 0 ? 1 : -1;
                 int horizontalSign = startX == 0 ? 1 : -1;
 
-                // check first and last pixel, these are known:
-                Assert.Equal(red, image[startX, startY]);
-                Assert.Equal(yellow, image[endX, endY]);
-
                 for (int i = 0; i < image.Height; i++)
                 {
                     // it's diagonal, so for any (a, a) on the gradient line, for all (a-x, b+x) - +/- depending on the diagonal direction - must be the same color)