Added support for custom pixel modifiers

src/ImageSharp/Processing/Processors/Effects/PixelShaderProcessor.cs

@@ -11,6 +11,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     /// </summary>
     public sealed class PixelShaderProcessor : IImageProcessor
     {
+        /// <summary>
+        /// The default <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.
+        /// </summary>
+        public const PixelConversionModifiers DefaultModifiers = PixelConversionModifiers.None;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelShaderProcessor"/> class.
         /// </summary>
@@ -20,6 +25,20 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         public PixelShaderProcessor(PixelShader pixelShader)
         {
             this.PixelShader = pixelShader;
+            this.Modifiers = DefaultModifiers;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PixelShaderProcessor"/> class.
+        /// </summary>
+        /// <param name="pixelShader">
+        /// The user defined pixel shader to use to modify images.
+        /// </param>
+        /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
+        public PixelShaderProcessor(PixelShader pixelShader, PixelConversionModifiers modifiers)
+        {
+            this.PixelShader = pixelShader;
+            this.Modifiers = modifiers;
         }
 
         /// <summary>
@@ -27,6 +46,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         /// </summary>
         public PixelShader PixelShader { get; }
 
+        /// <summary>
+        /// Gets the <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.
+        /// </summary>
+        public PixelConversionModifiers Modifiers { get; }
+
         /// <inheritdoc />
         public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>(Image<TPixel> source, Rectangle sourceRectangle)
             where TPixel : struct, IPixel<TPixel>

src/ImageSharp/Processing/Processors/Effects/PixelShaderProcessorBase.cs

@@ -18,14 +18,21 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     internal abstract class PixelShaderProcessorBase<TPixel> : ImageProcessor<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
+        /// <summary>
+        /// The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.
+        /// </summary>
+        private readonly PixelConversionModifiers modifiers;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelShaderProcessorBase{TPixel}"/> class.
         /// </summary>
+        /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
         /// <param name="source">The source <see cref="Image{TPixel}"/> for the current processor instance.</param>
         /// <param name="sourceRectangle">The source area to process for the current processor instance.</param>
-        protected PixelShaderProcessorBase(Image<TPixel> source, Rectangle sourceRectangle)
+        protected PixelShaderProcessorBase(PixelConversionModifiers modifiers, Image<TPixel> source, Rectangle sourceRectangle)
             : base(source, sourceRectangle)
         {
+            this.modifiers = modifiers;
         }
 
         /// <inheritdoc/>
@@ -44,12 +51,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
                         Span<Vector4> vectorSpan = vectorBuffer.Span;
                         int length = vectorSpan.Length;
                         Span<TPixel> rowSpan = source.GetPixelRowSpan(y).Slice(startX, length);
-                        PixelOperations<TPixel>.Instance.ToVector4(this.Configuration, rowSpan, vectorSpan);
+                        PixelOperations<TPixel>.Instance.ToVector4(this.Configuration, rowSpan, vectorSpan, this.modifiers);
 
                         // Run the user defined pixel shader on the current row of pixels
                         this.ApplyPixelShader(vectorSpan, y, startX);
 
-                        PixelOperations<TPixel>.Instance.FromVector4Destructive(this.Configuration, vectorSpan, rowSpan);
+                        PixelOperations<TPixel>.Instance.FromVector4Destructive(this.Configuration, vectorSpan, rowSpan, this.modifiers);
                     }
                 });
         }

src/ImageSharp/Processing/Processors/Effects/PixelShaderProcessor{TPixel}.cs

@@ -28,7 +28,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         /// <param name="source">The source <see cref="Image{TPixel}"/> for the current processor instance.</param>
         /// <param name="sourceRectangle">The source area to process for the current processor instance.</param>
         public PixelShaderProcessor(PixelShaderProcessor definition, Image<TPixel> source, Rectangle sourceRectangle)
-            : base(source, sourceRectangle)
+            : base(definition.Modifiers, source, sourceRectangle)
         {
             this.pixelShader = definition.PixelShader;
         }

src/ImageSharp/Processing/Processors/Effects/PositionAwarePixelShaderProcessor.cs

@@ -11,6 +11,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     /// </summary>
     public sealed class PositionAwarePixelShaderProcessor : IImageProcessor
     {
+        /// <summary>
+        /// The default <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.
+        /// </summary>
+        public const PixelConversionModifiers DefaultModifiers = PixelConversionModifiers.None;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PositionAwarePixelShaderProcessor"/> class.
         /// </summary>
@@ -20,6 +25,20 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         public PositionAwarePixelShaderProcessor(PositionAwarePixelShader pixelShader)
         {
             this.PixelShader = pixelShader;
+            this.Modifiers = DefaultModifiers;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PositionAwarePixelShaderProcessor"/> class.
+        /// </summary>
+        /// <param name="pixelShader">
+        /// The user defined pixel shader to use to modify images.
+        /// </param>
+        /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
+        public PositionAwarePixelShaderProcessor(PositionAwarePixelShader pixelShader, PixelConversionModifiers modifiers)
+        {
+            this.PixelShader = pixelShader;
+            this.Modifiers = modifiers;
         }
 
         /// <summary>
@@ -27,6 +46,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         /// </summary>
         public PositionAwarePixelShader PixelShader { get; }
 
+        /// <summary>
+        /// Gets the <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.
+        /// </summary>
+        public PixelConversionModifiers Modifiers { get; }
+
         /// <inheritdoc />
         public IImageProcessor<TPixel> CreatePixelSpecificProcessor<TPixel>(Image<TPixel> source, Rectangle sourceRectangle)
             where TPixel : struct, IPixel<TPixel>

src/ImageSharp/Processing/Processors/Effects/PositionAwarePixelShaderProcessor{TPixel}.cs

@@ -28,7 +28,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         /// <param name="source">The source <see cref="Image{TPixel}"/> for the current processor instance.</param>
         /// <param name="sourceRectangle">The source area to process for the current processor instance.</param>
         public PositionAwarePixelShaderProcessor(PositionAwarePixelShaderProcessor definition, Image<TPixel> source, Rectangle sourceRectangle)
-            : base(source, sourceRectangle)
+            : base(definition.Modifiers, source, sourceRectangle)
         {
             this.pixelShader = definition.PixelShader;
         }