Added new pixel shader extension methods

src/ImageSharp/Processing/Extensions/PixelShaderExtensions.cs

@@ -30,7 +30,28 @@ namespace SixLabors.ImageSharp.Processing
         /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
         /// </param>
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
-        public static IImageProcessingContext BlackWhite(this IImageProcessingContext source, PixelShader pixelShader, Rectangle rectangle)
+        public static IImageProcessingContext ApplyPixelShaderProcessor(this IImageProcessingContext source, PixelShader pixelShader, Rectangle rectangle)
             => source.ApplyProcessor(new PixelShaderProcessor(pixelShader), rectangle);
+
+        /// <summary>
+        /// Applies a user defined pixel shader to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="pixelShader">The user defined pixel shader to use to modify images.</param>
+        /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
+        public static IImageProcessingContext ApplyPixelShaderProcessor(this IImageProcessingContext source, PositionAwarePixelShader pixelShader)
+            => source.ApplyProcessor(new PositionAwarePixelShaderProcessor(pixelShader));
+
+        /// <summary>
+        /// Applies a user defined pixel shader to the image.
+        /// </summary>
+        /// <param name="source">The image this method extends.</param>
+        /// <param name="pixelShader">The user defined pixel shader to use to modify images.</param>
+        /// <param name="rectangle">
+        /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
+        /// </param>
+        /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
+        public static IImageProcessingContext ApplyPixelShaderProcessor(this IImageProcessingContext source, PositionAwarePixelShader pixelShader, Rectangle rectangle)
+            => source.ApplyProcessor(new PositionAwarePixelShaderProcessor(pixelShader), rectangle);
     }
 }