SIMD optimisations

Former-commit-id: 84d7baf1143adab15d23d4bbc5011ac2e70364c1
Former-commit-id: 8510f8d406386e97d26b5e4a28044cfb61e9ff88
Former-commit-id: a2ae716d4495a9c2a1d6334838c5103ec4f0190e

src/ImageProcessor/Colors/Color.cs

@@ -211,17 +211,7 @@ namespace ImageProcessor
         /// <summary>
         /// Gets this color with the component values clamped from 0 to 1.
         /// </summary>
-        public Color Limited
-        {
-            get
-            {
-                float r = this.R.Clamp(0, 1);
-                float g = this.G.Clamp(0, 1);
-                float b = this.B.Clamp(0, 1);
-                float a = this.A.Clamp(0, 1);
-                return new Color(r, g, b, a);
-            }
-        }
+        public Color Limited => new Color(Vector4.Clamp(this.backingVector, Vector4.Zero, Vector4.One));
 
         /// <summary>
         /// Computes the product of multiplying a color by a given factor.
@@ -402,7 +392,7 @@ namespace ImageProcessor
         public static Color FromNonPremultiplied(Color color)
         {
             float a = color.A;
-            return new Color(color.R * a, color.G * a, color.B * a, a);
+            return new Color(color.backingVector * new Vector4(a, a, a, 1));
         }
 
         /// <summary>
@@ -416,10 +406,10 @@ namespace ImageProcessor
             float a = color.A;
             if (Math.Abs(a) < Epsilon)
             {
-                return new Color(color.R, color.G, color.B, a);
+                return new Color(color.backingVector);
             }
 
-            return new Color(color.R / a, color.G / a, color.B / a, a);
+            return new Color(color.backingVector / new Vector4(a, a, a, 1));
         }
 
         /// <summary>

src/ImageProcessor/Filters/Alpha.cs

@@ -6,6 +6,7 @@
 namespace ImageProcessor.Filters
 {
     using System;
+    using System.Numerics;
     using System.Threading.Tasks;
 
     /// <summary>
@@ -39,6 +40,7 @@ namespace ImageProcessor.Filters
             int sourceBottom = sourceRectangle.Bottom;
             int startX = sourceRectangle.X;
             int endX = sourceRectangle.Right;
+            Vector4 alphaVector = new Vector4(1, 1, 1, alpha);
 
             Parallel.For(
                 startY,
@@ -49,10 +51,9 @@ namespace ImageProcessor.Filters
                         {
                             for (int x = startX; x < endX; x++)
                             {
-                                Color color = Color.ToNonPremultiplied(source[x, y]);
-                                color.A = color.A * alpha;
-                                color = Color.FromNonPremultiplied(color);
-                                target[x, y] = color;
+                                Vector4 color = Color.ToNonPremultiplied(source[x, y]).ToVector4();
+                                color *= alphaVector;
+                                target[x, y] = Color.FromNonPremultiplied(new Color(color));
                             }
                         }
                     });

src/ImageProcessor/Filters/BackgroundColor.cs

@@ -51,13 +51,14 @@ namespace ImageProcessor.Filters
                         for (int x = startX; x < endX; x++)
                         {
                             Color color = source[x, y];
+                            float a = color.A;
 
-                            if (color.A < 1 && color.A > 0)
+                            if (a < 1 && a > 0)
                             {
                                 color = Color.Lerp(color, backgroundColor, .5f);
                             }
 
-                            if (Math.Abs(color.A) < Epsilon)
+                            if (Math.Abs(a) < Epsilon)
                             {
                                 color = backgroundColor;
                             }

src/ImageProcessor/Filters/Binarization/Threshold.cs

@@ -6,6 +6,7 @@
 namespace ImageProcessor.Filters
 {
     using System;
+    using System.Numerics;
     using System.Threading.Tasks;
 
     /// <summary>

src/ImageProcessor/Filters/Contrast.cs

@@ -6,6 +6,7 @@
 namespace ImageProcessor.Filters
 {
     using System;
+    using System.Numerics;
     using System.Threading.Tasks;
 
     /// <summary>
@@ -39,7 +40,8 @@ namespace ImageProcessor.Filters
             int sourceBottom = sourceRectangle.Bottom;
             int startX = sourceRectangle.X;
             int endX = sourceRectangle.Right;
-
+            Vector4 contrastVector = new Vector4(contrast, contrast, contrast, 1);
+            Vector4 shiftVector = new Vector4(.5f, .5f, .5f, 1);
             Parallel.For(
                 startY,
                 endY,
@@ -49,22 +51,11 @@ namespace ImageProcessor.Filters
                         {
                             for (int x = startX; x < endX; x++)
                             {
-                                Color color = Color.Expand(source[x, y]);
-
-                                // Seems to be faster than Vector3.
-                                color.R -= 0.5f;
-                                color.R *= contrast;
-                                color.R += 0.5f;
-
-                                color.G -= 0.5f;
-                                color.G *= contrast;
-                                color.G += 0.5f;
-
-                                color.B -= 0.5f;
-                                color.B *= contrast;
-                                color.B += 0.5f;
-
-                                target[x, y] = Color.Compress(color);
+                                Vector4 color = Color.Expand(source[x, y]).ToVector4();
+                                color -= shiftVector;
+                                color *= contrastVector;
+                                color += shiftVector;
+                                target[x, y] = Color.Compress(new Color(color));
                             }
                         }
                     });

src/ImageProcessor/Filters/Invert.cs

@@ -5,6 +5,7 @@
 
 namespace ImageProcessor.Filters
 {
+    using System.Numerics;
     using System.Threading.Tasks;
 
     /// <summary>
@@ -19,6 +20,7 @@ namespace ImageProcessor.Filters
             int sourceBottom = sourceRectangle.Bottom;
             int startX = sourceRectangle.X;
             int endX = sourceRectangle.Right;
+            Vector3 inverseVector = Vector3.One;
 
             Parallel.For(
                 startY,
@@ -30,10 +32,8 @@ namespace ImageProcessor.Filters
                             for (int x = startX; x < endX; x++)
                             {
                                 Color color = source[x, y];
-                                color.R = 1 - color.R;
-                                color.G = 1 - color.G;
-                                color.B = 1 - color.B;
-                                target[x, y] = color;
+                                Vector3 vector = inverseVector - color.ToVector3();
+                                target[x, y] = new Color(vector, color.A);
                             }
                         }
                     });

src/ImageProcessor/Formats/Gif/Quantizer/OctreeQuantizer.cs

@@ -60,6 +60,11 @@ namespace ImageProcessor.Formats
             this.maxColors = maxColors;
         }
 
+        /// <summary>
+        /// Gets or sets the transparency threshold.
+        /// </summary>
+        public byte Threshold { get; set; } = 128;
+
         /// <summary>
         /// Process the pixel in the first pass of the algorithm
         /// </summary>
@@ -91,7 +96,7 @@ namespace ImageProcessor.Formats
             byte paletteIndex = (byte)this.maxColors;
 
             // Get the palette index if it's transparency meets criterea.
-            if (pixel.A > 0)
+            if (pixel.A > this.Threshold)
             {
                 paletteIndex = (byte)this.octree.GetPaletteIndex(pixel);
             }

src/ImageProcessor/Samplers/Resampler.cs

@@ -9,6 +9,8 @@ namespace ImageProcessor.Samplers
     using System.Collections.Generic;
     using System.Threading.Tasks;
 
+    using ImageProcessor.Filters;
+
     /// <summary>
     /// Provides methods that allow the resampling of images using various algorithms.
     /// </summary>
@@ -81,6 +83,8 @@ namespace ImageProcessor.Samplers
                 this.horizontalWeights = this.PrecomputeWeights(targetRectangle.Width, sourceRectangle.Width);
                 this.verticalWeights = this.PrecomputeWeights(targetRectangle.Height, sourceRectangle.Height);
             }
+
+            new BackgroundColor(Color.Transparent).Apply(source, source, sourceRectangle);
         }
 
         /// <inheritdoc/>
@@ -189,10 +193,6 @@ namespace ImageProcessor.Samplers
                             }
 
                             destination = Color.Compress(destination);
-
-                            // Round alpha values in an attempt to prevent bleed.
-                            destination.A = (float)Math.Round(destination.A, 2);
-
                             target[x, y] = destination;
                         }
                     }
@@ -304,9 +304,6 @@ namespace ImageProcessor.Samplers
                             }
 
                             destination = Color.Compress(destination);
-
-                            // Round alpha values in an attempt to prevent bleed.
-                            destination.A = (float)Math.Round(destination.A, 2);
                             target[x, y] = destination;
                         }
                     }