Added progress callback to IImageProcessor and ParallelImageProcessor

Former-commit-id: 837027deaf8f46ed9dc6b9adf50d7fa3596de04d
Former-commit-id: cc005f037f4e6d9ead5763ab73c49abe09aadbe4
Former-commit-id: 2036768cdc0c07c71f746a5c0eb64633c2893f3a

src/ImageProcessor/Filters/Brightness.cs

@@ -57,6 +57,7 @@ namespace ImageProcessor.Filters
 
                                 target[x, y] = Color.Compress(new Color(vector3, color.A));
                             }
+                            this.OnRowProcessed();
                         }
                     });
         }

src/ImageProcessor/IImageProcessor.cs

@@ -5,11 +5,28 @@
 
 namespace ImageProcessor
 {
+    public struct ProgressedEventArgs
+    {
+        public int numRowsProcessed;
+        public int totalRows;
+    }
+
+    public delegate void ProgressedEventHandler(object sender, ProgressedEventArgs e);
+
     /// <summary>
     /// Encapsulates methods to alter the pixels of an image.
     /// </summary>
     public interface IImageProcessor
     {
+        /// <summary>
+        /// Event fires when each row of the source image has been processed.
+        /// </summary>
+        /// <remarks>
+        /// This event may be called from threads other than the client thread, and from multiple threads simultaneously.
+        /// Individual row notifications may arrived out of order.
+        /// </remarks>
+        event ProgressedEventHandler OnProgressed;
+
         /// <summary>
         /// Applies the process to the specified portion of the specified <see cref="ImageBase"/>.
         /// </summary>

src/ImageProcessor/ParallelImageProcessor.cs

@@ -6,6 +6,7 @@
 namespace ImageProcessor
 {
     using System;
+    using System.Threading;
     using System.Threading.Tasks;
 
     /// <summary>
@@ -13,11 +14,38 @@ namespace ImageProcessor
     /// </summary>
     public abstract class ParallelImageProcessor : IImageProcessor
     {
+        /// <inheritdoc/>
+        public event ProgressedEventHandler OnProgressed;
+
         /// <summary>
         /// Gets or sets the count of workers to run the process in parallel.
         /// </summary>
         public virtual int Parallelism { get; set; } = Environment.ProcessorCount * 2;
 
+        /// <summary>
+        /// The number of rows processed by a derived class.
+        /// </summary>
+        private int numRowsProcessed;
+
+        /// <summary>
+        /// The total number of rows that will be processed by a derived class.
+        /// </summary>
+        private int totalRows;
+
+        /// <summary>
+        /// Must be called by derived classes after processing a single row.
+        /// </summary>
+        protected void OnRowProcessed()
+        {
+            if(this.OnProgressed != null)
+            {
+                int currThreadNumRows = Interlocked.Add(ref this.numRowsProcessed, 1);
+
+                // Report progress. This may be on the client's thread, or on a Task library thread.
+                this.OnProgressed(this, new ProgressedEventArgs { numRowsProcessed = currThreadNumRows, totalRows = this.totalRows });
+            }
+        }
+
         /// <inheritdoc/>
         public void Apply(ImageBase target, ImageBase source, Rectangle sourceRectangle)
         {
@@ -26,6 +54,9 @@ namespace ImageProcessor
             Image temp = frame != null ? new Image(frame) : new Image((Image)source);
             this.OnApply(temp, target, target.Bounds, sourceRectangle);
 
+            this.numRowsProcessed = 0;
+            this.totalRows = sourceRectangle.Height;
+
             if (this.Parallelism > 1)
             {
                 int partitionCount = this.Parallelism;
@@ -72,6 +103,8 @@ namespace ImageProcessor
             this.OnApply(temp, target, target.Bounds, sourceRectangle);
 
             targetRectangle = target.Bounds;
+            this.numRowsProcessed = 0;
+            this.totalRows = targetRectangle.Bottom;
 
             if (this.Parallelism > 1)
             {

tests/ImageProcessor.Tests/Processors/Filters/FilterTests.cs

@@ -1,6 +1,7 @@
 
 namespace ImageProcessor.Tests
 {
+    using System;
     using System.Diagnostics;
     using System.IO;
 
@@ -65,12 +66,25 @@ namespace ImageProcessor.Tests
                     string filename = Path.GetFileNameWithoutExtension(file) + "-" + name + Path.GetExtension(file);
                     using (FileStream output = File.OpenWrite($"TestOutput/Filter/{ Path.GetFileName(filename) }"))
                     {
+                        lastRowProcessed = 0;
+                        processor.OnProgressed += ProgressUpdate;
                         image.Process(processor).Save(output);
+                        processor.OnProgressed -= ProgressUpdate;
                     }
 
                     Trace.WriteLine($"{ name }: { watch.ElapsedMilliseconds}ms");
                 }
             }
         }
+
+        private static int allowedVariability = Environment.ProcessorCount * 4;
+        private int lastRowProcessed;
+
+        private void ProgressUpdate(object sender, ProgressedEventArgs e)
+        {
+            Assert.InRange(e.numRowsProcessed, 1, e.totalRows);
+            Assert.InRange(e.numRowsProcessed, lastRowProcessed - allowedVariability, lastRowProcessed + allowedVariability);
+            lastRowProcessed = e.numRowsProcessed;
+        }
     }
 }