Add CroppedRegionChanged event for ImageCropper.

Microsoft.Toolkit.Uwp.UI.Controls/ImageCropper/ImageCropper.Events.cs

@@ -103,7 +103,7 @@ private void ImageCropperThumb_KeyUp(object sender, KeyRoutedEventArgs e)
             if (croppedRect.Width > MinCropSize.Width && croppedRect.Height > MinCropSize.Height)
             {
                 croppedRect.Intersect(_restrictedCropRect);
-                _currentCroppedRect = croppedRect;
+                CroppedRegion = croppedRect;
             }
 
             UpdateImageLayout(true);
@@ -116,7 +116,7 @@ private void ImageCropperThumb_ManipulationCompleted(object sender, Manipulation
             if (croppedRect.Width > MinCropSize.Width && croppedRect.Height > MinCropSize.Height)
             {
                 croppedRect.Intersect(_restrictedCropRect);
-                _currentCroppedRect = croppedRect;
+                CroppedRegion = croppedRect;
             }
 
             UpdateImageLayout(true);
@@ -160,7 +160,7 @@ private void SourceImage_ManipulationDelta(object sender, ManipulationDeltaRoute
             selectedRect.Y += offsetY;
             var croppedRect = _inverseImageTransform.TransformBounds(selectedRect);
             croppedRect.Intersect(_restrictedCropRect);
-            _currentCroppedRect = croppedRect;
+            CroppedRegion = croppedRect;
             UpdateImageLayout();
         }
 

Microsoft.Toolkit.Uwp.UI.Controls/ImageCropper/ImageCropper.Logic.cs

@@ -28,7 +28,7 @@ private void InitImageLayout(bool animate = false)
                 _restrictedCropRect = new Rect(0, 0, Source.PixelWidth, Source.PixelHeight);
                 if (IsValidRect(_restrictedCropRect))
                 {
-                    _currentCroppedRect = KeepAspectRatio ? GetUniformRect(_restrictedCropRect, UsedAspectRatio) : _restrictedCropRect;
+                    CroppedRegion = KeepAspectRatio ? GetUniformRect(_restrictedCropRect, UsedAspectRatio) : _restrictedCropRect;
                     UpdateImageLayout(animate);
                 }
             }
@@ -44,8 +44,8 @@ private void UpdateImageLayout(bool animate = false)
         {
             if (Source != null && IsValidRect(CanvasRect))
             {
-                var uniformSelectedRect = GetUniformRect(CanvasRect, _currentCroppedRect.Width / _currentCroppedRect.Height);
-                UpdateImageLayoutWithViewport(uniformSelectedRect, _currentCroppedRect, animate);
+                var uniformSelectedRect = GetUniformRect(CanvasRect, CroppedRegion.Width / CroppedRegion.Height);
+                UpdateImageLayoutWithViewport(uniformSelectedRect, CroppedRegion, animate);
             }
         }
 
@@ -69,7 +69,7 @@ private void UpdateImageLayoutWithViewport(Rect viewport, Rect viewportImageRect
             _inverseImageTransform.ScaleX = _inverseImageTransform.ScaleY = 1 / imageScale;
             _inverseImageTransform.TranslateX = -_imageTransform.TranslateX / imageScale;
             _inverseImageTransform.TranslateY = -_imageTransform.TranslateY / imageScale;
-            var selectedRect = _imageTransform.TransformBounds(_currentCroppedRect);
+            var selectedRect = _imageTransform.TransformBounds(CroppedRegion);
             _restrictedSelectRect = _imageTransform.TransformBounds(_restrictedCropRect);
             var startPoint = GetSafePoint(_restrictedSelectRect, new Point(selectedRect.X, selectedRect.Y));
             var endPoint = GetSafePoint(_restrictedSelectRect, new Point(
@@ -271,7 +271,7 @@ private void UpdateCroppedRect(ThumbPosition position, Point diffPos)
                 var croppedRect = _inverseImageTransform.TransformBounds(
                     new Rect(startPoint, endPoint));
                 croppedRect.Intersect(_restrictedCropRect);
-                _currentCroppedRect = croppedRect;
+                CroppedRegion = croppedRect;
                 var viewportRect = GetUniformRect(CanvasRect, selectedRect.Width / selectedRect.Height);
                 var viewportImgRect = _inverseImageTransform.TransformBounds(selectedRect);
                 UpdateImageLayoutWithViewport(viewportRect, viewportImgRect);
@@ -557,7 +557,7 @@ private void UpdateAspectRatio(bool animate = false)
 
                 var croppedRect = _inverseImageTransform.TransformBounds(uniformSelectedRect);
                 croppedRect.Intersect(_restrictedCropRect);
-                _currentCroppedRect = croppedRect;
+                CroppedRegion = croppedRect;
                 UpdateImageLayout(animate);
             }
         }

Microsoft.Toolkit.Uwp.UI.Controls/ImageCropper/ImageCropper.Properties.cs

@@ -25,11 +25,6 @@ public partial class ImageCropper
         /// </summary>
         public double MinSelectedLength { get; set; } = 40;
 
-        /// <summary>
-        /// Gets the current cropped region.
-        /// </summary>
-        public Rect CroppedRegion => _currentCroppedRect;
-
         private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
             var target = (ImageCropper)d;
@@ -64,6 +59,13 @@ private static void OnCropShapeChanged(
             target.UpdateMaskArea();
         }
 
+        private static void OnCroppedRegionChanged(
+            DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var target = (ImageCropper)d;
+            target.CroppedRegionChanged?.Invoke(target, new ImageCropperCroppedRegionChangedEventArgs { OldRegion = (Rect)e.OldValue, NewRegion = (Rect)e.NewValue });
+        }
+
         private static void OnThumbPlacementChanged(
             DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
@@ -99,6 +101,15 @@ public CropShape CropShape
             set { SetValue(CropShapeProperty, value); }
         }
 
+        /// <summary>
+        /// Gets the current cropped region.
+        /// </summary>
+        public Rect CroppedRegion
+        {
+            get { return (Rect)GetValue(CroppedRegionProperty); }
+            private set { SetValue(CroppedRegionProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the mask on the cropped image.
         /// </summary>
@@ -153,6 +164,12 @@ public ThumbPlacement ThumbPlacement
         public static readonly DependencyProperty CropShapeProperty =
             DependencyProperty.Register(nameof(CropShape), typeof(CropShape), typeof(ImageCropper), new PropertyMetadata(default(CropShape), OnCropShapeChanged));
 
+        /// <summary>
+        /// Identifies the <see cref="CroppedRegion"/> dependency property.
+        /// </summary>
+        public static readonly DependencyProperty CroppedRegionProperty =
+            DependencyProperty.Register(nameof(CroppedRegion), typeof(Rect), typeof(ImageCropper), new PropertyMetadata(Rect.Empty, OnCroppedRegionChanged));
+
         /// <summary>
         /// Identifies the <see cref="Mask"/> dependency property.
         /// </summary>

Microsoft.Toolkit.Uwp.UI.Controls/ImageCropper/ImageCropper.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Threading.Tasks;
 using Windows.Foundation;
-using Windows.Graphics.Imaging;
 using Windows.Storage;
 using Windows.Storage.Streams;
 using Windows.UI.Xaml;
@@ -54,7 +53,6 @@ public partial class ImageCropper : Control
         private double _startY;
         private double _endX;
         private double _endY;
-        private Rect _currentCroppedRect = Rect.Empty;
         private Rect _restrictedCropRect = Rect.Empty;
         private Rect _restrictedSelectRect = Rect.Empty;
         private RectangleGeometry _outerGeometry;
@@ -69,6 +67,11 @@ public ImageCropper()
             DefaultStyleKey = typeof(ImageCropper);
         }
 
+        /// <summary>
+        /// Occurs when the <see cref="CroppedRegion"/> property has changed.
+        /// </summary>
+        public event TypedEventHandler<ImageCropper, ImageCropperCroppedRegionChangedEventArgs> CroppedRegionChanged;
+
         private Rect CanvasRect => new Rect(0, 0, _imageCanvas?.ActualWidth ?? 0, _imageCanvas?.ActualHeight ?? 0);
 
         private bool KeepAspectRatio => UsedAspectRatio > 0;
@@ -398,11 +401,11 @@ public async Task SaveAsync(IRandomAccessStream stream, BitmapFileFormat bitmapF
 
             if (keepRectangularOutput || CropShape == CropShape.Rectangular)
             {
-                await CropImageAsync(Source, stream, _currentCroppedRect, bitmapFileFormat);
+                await CropImageAsync(Source, stream, CroppedRegion, bitmapFileFormat);
                 return;
             }
 
-            await CropImageWithShapeAsync(Source, stream, _currentCroppedRect, bitmapFileFormat, CropShape);
+            await CropImageWithShapeAsync(Source, stream, CroppedRegion, bitmapFileFormat, CropShape);
         }
 
         /// <summary>
@@ -439,7 +442,7 @@ public bool TrySetCroppedRegion(Rect rect)
                 return false;
             }
 
-            _currentCroppedRect = rect;
+            CroppedRegion = rect;
             UpdateImageLayout(true);
             return true;
         }

Microsoft.Toolkit.Uwp.UI.Controls/ImageCropper/ImageCropperCroppedRegionChangedEventArgs.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Windows.Foundation;
+
+namespace Microsoft.Toolkit.Uwp.UI.Controls
+{
+    /// <summary>
+    ///为< 请参阅cref = “ ImageCropper.CroppedRegionChanged ” />事件提供事件数据。 
+    /// </summary>
+    public sealed class ImageCropperCroppedRegionChangedEventArgs
+    {
+        /// <summary>
+        /// Gets the region that is currently cropped in the control.
+        /// </summary>
+        public Rect NewRegion { get; internal set; }
+
+        /// <summary>
+        /// Gets the region that was previously cropped in the control.
+        /// </summary>
+        public Rect OldRegion { get; internal set; }
+    }
+}