基于WPF實現(xiàn)裁剪圖像功能

更新時間：2023年06月07日 08:51:51 作者：WPF開發(fā)者

這篇文章主要為大家詳細介紹了如何基于WPF實現(xiàn)裁剪圖像功能，文中的示例代碼講解詳細，對我們學(xué)習或工作有一定幫助，感興趣的小伙伴可以了解一下

WPF 實現(xiàn)裁剪圖像

框架使用.NET4 至 .NET6

Visual Studio 2022

使用 Canvas 展示選擇的裁剪圖片

使用 4 個 Rectangle 設(shè)置未選中區(qū)域分別是左上右下

中間展示當前的裁剪區(qū)域使用了 Border 移動

左右移動使用 Canvas.SetLeft
上下移動使用 Canvas.SetTop
Border 獲取裁剪區(qū)域獲取GetLeft、GetTop、Border的Width與Height

拉伸 Border 使用了之前截圖控件使用的裝飾器 ScreenCutAdorner

新增裝飾器不允許拉伸超出 Canvas 畫布

實現(xiàn)代碼

1）新建 CropImage.cs 控件代碼如下:

using?System;
using?System.Windows;
using?System.Windows.Controls;
using?System.Windows.Documents;
using?System.Windows.Input;
using?System.Windows.Media;
using?System.Windows.Media.Imaging;
using?System.Windows.Shapes;
using?WPFDevelopers.Helpers;
namespace?WPFDevelopers.Controls
{
????[TemplatePart(Name?=?CanvasTemplateName,?Type?=?typeof(Canvas))]
????[TemplatePart(Name?=?RectangleLeftTemplateName,?Type?=?typeof(Rectangle))]
????[TemplatePart(Name?=?RectangleTopTemplateName,?Type?=?typeof(Rectangle))]
????[TemplatePart(Name?=?RectangleRightTemplateName,?Type?=?typeof(Rectangle))]
????[TemplatePart(Name?=?RectangleBottomTemplateName,?Type?=?typeof(Rectangle))]
????[TemplatePart(Name?=?BorderTemplateName,?Type?=?typeof(Border))]
????public?class?CropImage?:?Control
????{
????????private?const?string?CanvasTemplateName?=?"PART_Canvas";
????????private?const?string?RectangleLeftTemplateName?=?"PART_RectangleLeft";
????????private?const?string?RectangleTopTemplateName?=?"PART_RectangleTop";
????????private?const?string?RectangleRightTemplateName?=?"PART_RectangleRight";
????????private?const?string?RectangleBottomTemplateName?=?"PART_RectangleBottom";
????????private?const?string?BorderTemplateName?=?"PART_Border";
????????private?BitmapFrame?bitmapFrame;
????????private?Rectangle?_rectangleLeft,?_rectangleTop,?_rectangleRight,?_rectangleBottom;
????????private?Border?_border;
????????private?Canvas?_canvas;
????????public?ImageSource?Source
????????{
????????????get?{?return?(ImageSource)GetValue(SourceProperty);?}
????????????set?{?SetValue(SourceProperty,?value);?}
????????}
????????public?static?readonly?DependencyProperty?SourceProperty?=
????????????DependencyProperty.Register("Source",?typeof(ImageSource),?typeof(CropImage),?new?PropertyMetadata(null,?OnSourceChanged));
????????public?Rect?CurrentRect
????????{
????????????get?{?return?(Rect)GetValue(CurrentRectProperty);?}
????????????private?set?{?SetValue(CurrentRectProperty,?value);?}
????????}
????????public?static?readonly?DependencyProperty?CurrentRectProperty?=
????????????DependencyProperty.Register("CurrentRect",?typeof(Rect),?typeof(CropImage),?new?PropertyMetadata(null));
????????public?ImageSource?CurrentAreaBitmap
????????{
????????????get?{?return?(ImageSource)GetValue(CurrentAreaBitmapProperty);?}
????????????private?set?{?SetValue(CurrentAreaBitmapProperty,?value);?}
????????}
????????public?static?readonly?DependencyProperty?CurrentAreaBitmapProperty?=
????????????DependencyProperty.Register("CurrentAreaBitmap",?typeof(ImageSource),?typeof(CropImage),?new?PropertyMetadata(null));
????????private?AdornerLayer?adornerLayer;
????????private?ScreenCutAdorner?screenCutAdorner;
????????private?bool?isDragging;
????????private?double?offsetX,?offsetY;
????????private?static?void?OnSourceChanged(DependencyObject?d,?DependencyPropertyChangedEventArgs?e)
????????{
????????????var?crop?=?(CropImage)d;
????????????if?(crop?!=?null)
????????????????crop.DrawImage();
????????}
????????static?CropImage()
????????{
????????????DefaultStyleKeyProperty.OverrideMetadata(typeof(CropImage),
????????????????new?FrameworkPropertyMetadata(typeof(CropImage)));
????????}
????????public?override?void?OnApplyTemplate()
????????{
????????????base.OnApplyTemplate();
????????????_canvas?=?GetTemplateChild(CanvasTemplateName)?as?Canvas;
????????????_rectangleLeft?=?GetTemplateChild(RectangleLeftTemplateName)?as?Rectangle;
????????????_rectangleTop?=?GetTemplateChild(RectangleTopTemplateName)?as?Rectangle;
????????????_rectangleRight?=?GetTemplateChild(RectangleRightTemplateName)?as?Rectangle;
????????????_rectangleBottom?=?GetTemplateChild(RectangleBottomTemplateName)?as?Rectangle;
????????????_border?=?GetTemplateChild(BorderTemplateName)?as?Border;
????????????DrawImage();
????????}
????????void?DrawImage()
????????{
????????????if?(Source?==?null)
????????????{
????????????????_border.Visibility?=?Visibility.Collapsed;
????????????????if?(adornerLayer?==?null)?return;
????????????????adornerLayer.Remove(screenCutAdorner);
????????????????screenCutAdorner?=?null;
????????????????adornerLayer?=?null;
????????????????return;
????????????}
????????????_border.Visibility?=?Visibility.Visible;
????????????var?bitmap?=?(BitmapImage)Source;
????????????bitmapFrame?=?ControlsHelper.CreateResizedImage(bitmap,?(int)bitmap.Width,?(int)bitmap.Height,?0);
????????????_canvas.Width?=?bitmap.Width;
????????????_canvas.Height?=?bitmap.Height;
????????????_canvas.Background?=?new?ImageBrush(bitmap);
????????????_border.Width?=?bitmap.Width?*?0.2;
????????????_border.Height?=?bitmap.Height?*?0.2;
????????????var?cx?=?_canvas.Width?/?2?-?_border.Width?/?2;
????????????var?cy?=?_canvas.Height?/?2?-?_border.Height?/?2;
????????????Canvas.SetLeft(_border,?cx);
????????????Canvas.SetTop(_border,?cy);
????????????if?(adornerLayer?!=?null)?return;
????????????adornerLayer?=?AdornerLayer.GetAdornerLayer(_border);
????????????screenCutAdorner?=?new?ScreenCutAdorner(_border);
????????????adornerLayer.Add(screenCutAdorner);
????????????_border.SizeChanged?-=?Border_SizeChanged;
????????????_border.SizeChanged?+=?Border_SizeChanged;
????????????_border.MouseDown?-=?Border_MouseDown;
????????????_border.MouseDown?+=?Border_MouseDown;
????????????_border.MouseMove?-=?Border_MouseMove;
????????????_border.MouseMove?+=?Border_MouseMove;
????????????_border.MouseUp?-=?Border_MouseUp;
????????????_border.MouseUp?+=?Border_MouseUp;
????????}
????????private?void?Border_MouseUp(object?sender,?MouseButtonEventArgs?e)
????????{
????????????isDragging?=?false;
????????????var?draggableControl?=?sender?as?UIElement;
????????????draggableControl.ReleaseMouseCapture();
????????}
????????private?void?Border_MouseDown(object?sender,?MouseButtonEventArgs?e)
????????{
????????????if?(!isDragging)
????????????{
????????????????isDragging?=?true;
????????????????var?draggableControl?=?sender?as?UIElement;
????????????????var?position?=?e.GetPosition(this);
????????????????offsetX?=?position.X?-?Canvas.GetLeft(draggableControl);
????????????????offsetY?=?position.Y?-?Canvas.GetTop(draggableControl);
????????????????draggableControl.CaptureMouse();
????????????}
????????}
????????private?void?Border_MouseMove(object?sender,?MouseEventArgs?e)
????????{
????????????if?(isDragging?&&?e.LeftButton?==?MouseButtonState.Pressed)
????????????{
????????????????var?draggableControl?=?sender?as?UIElement;
????????????????var?position?=?e.GetPosition(this);
????????????????var?x?=?position.X?-?offsetX;
????????????????x?=?x?<?0???0?:?x;
????????????????x?=?x?+?_border.Width?>?_canvas.Width???_canvas.Width?-?_border.Width?:?x;
????????????????var?y?=?position.Y?-?offsetY;
????????????????y?=?y?<?0???0?:?y;
????????????????y?=?y?+?_border.Height?>?_canvas.Height???_canvas.Height?-?_border.Height?:?y;
????????????????Canvas.SetLeft(draggableControl,?x);
????????????????Canvas.SetTop(draggableControl,?y);
????????????????Render();
????????????}
????????}
????????void?Render()
????????{
????????????var?cy?=?Canvas.GetTop(_border);
????????????cy?=?cy?<?0???0?:?cy;
????????????var?borderLeft?=?Canvas.GetLeft(_border);
????????????borderLeft?=?borderLeft?<?0???0?:?borderLeft;
????????????_rectangleLeft.Width?=?borderLeft;
????????????_rectangleLeft.Height?=?_border.ActualHeight;
????????????Canvas.SetTop(_rectangleLeft,?cy);
????????????_rectangleTop.Width?=?_canvas.Width;
????????????_rectangleTop.Height?=?cy;
????????????var?rx?=?borderLeft?+?_border.ActualWidth;
????????????rx?=?rx?>?_canvas.Width???_canvas.Width?:?rx;
????????????_rectangleRight.Width?=?_canvas.Width?-?rx;
????????????_rectangleRight.Height?=?_border.ActualHeight;
????????????Canvas.SetLeft(_rectangleRight,?rx);
????????????Canvas.SetTop(_rectangleRight,?cy);
????????????var?by?=?cy?+?_border.ActualHeight;
????????????by?=?by?<?0???0?:?by;
????????????_rectangleBottom.Width?=?_canvas.Width;
????????????var?rby?=?_canvas.Height?-?by;
????????????_rectangleBottom.Height?=?rby?<?0???0?:?rby;
????????????Canvas.SetTop(_rectangleBottom,?by);
????????????var?bitmap?=?CutBitmap();
????????????if?(bitmap?==?null)?return;
????????????var?frame?=?BitmapFrame.Create(bitmap);
????????????CurrentAreaBitmap?=?frame;
????????}
????????private?void?Border_SizeChanged(object?sender,?SizeChangedEventArgs?e)
????????{
????????????Render();
????????}
????????private?CroppedBitmap?CutBitmap()
????????{
????????????var?width?=?_border.Width;
????????????var?height?=?_border.Height;
????????????if?(double.IsNaN(width)?||?double.IsNaN(height))
????????????????return?null;
????????????var?left?=?Canvas.GetLeft(_border);
????????????var?top?=?Canvas.GetTop(_border);
????????????CurrentRect?=?new?Rect(left,?top,?width,?height);
????????????return?new?CroppedBitmap(bitmapFrame,
???????????????new?Int32Rect((int)CurrentRect.X,?(int)CurrentRect.Y,?(int)CurrentRect.Width,?(int)CurrentRect.Height));
????????}
????}
}

2）修復(fù) ScreenCutAdorner.cs 裝飾器不允許超過 Canvas 代碼如下:

using?System;
using?System.Windows;
using?System.Windows.Controls;
using?System.Windows.Controls.Primitives;
using?System.Windows.Documents;
using?System.Windows.Input;
using?System.Windows.Media;
using?System.Windows.Shapes;
namespace?WPFDevelopers.Controls
{
????public?class?ScreenCutAdorner?:?Adorner
????{
????????private?const?double?THUMB_SIZE?=?15;
????????private?const?double?MINIMAL_SIZE?=?20;
????????private?readonly?Thumb?lc;
????????private?readonly?Thumb?tl;
????????private?readonly?Thumb?tc;
????????private?readonly?Thumb?tr;
????????private?readonly?Thumb?rc;
????????private?readonly?Thumb?br;
????????private?readonly?Thumb?bc;
????????private?readonly?Thumb?bl;
????????private?readonly?VisualCollection?visCollec;
????????private?readonly?Canvas?canvas;
????????public?ScreenCutAdorner(UIElement?adorned)?:?base(adorned)
????????{
????????????canvas?=?FindParent(adorned)?as?Canvas;
????????????visCollec?=?new?VisualCollection(this);
????????????visCollec.Add(lc?=?GetResizeThumb(Cursors.SizeWE,?HorizontalAlignment.Left,?VerticalAlignment.Center));
????????????visCollec.Add(tl?=?GetResizeThumb(Cursors.SizeNWSE,?HorizontalAlignment.Left,?VerticalAlignment.Top));
????????????visCollec.Add(tc?=?GetResizeThumb(Cursors.SizeNS,?HorizontalAlignment.Center,?VerticalAlignment.Top));
????????????visCollec.Add(tr?=?GetResizeThumb(Cursors.SizeNESW,?HorizontalAlignment.Right,?VerticalAlignment.Top));
????????????visCollec.Add(rc?=?GetResizeThumb(Cursors.SizeWE,?HorizontalAlignment.Right,?VerticalAlignment.Center));
????????????visCollec.Add(br?=?GetResizeThumb(Cursors.SizeNWSE,?HorizontalAlignment.Right,?VerticalAlignment.Bottom));
????????????visCollec.Add(bc?=?GetResizeThumb(Cursors.SizeNS,?HorizontalAlignment.Center,?VerticalAlignment.Bottom));
????????????visCollec.Add(bl?=?GetResizeThumb(Cursors.SizeNESW,?HorizontalAlignment.Left,?VerticalAlignment.Bottom));
????????}
????????private?static?UIElement?FindParent(UIElement?element)
????????{
????????????DependencyObject?obj?=?element;
????????????obj?=?VisualTreeHelper.GetParent(obj);
????????????return?obj?as?UIElement;
????????}
????????protected?override?int?VisualChildrenCount?=>?visCollec.Count;
????????protected?override?Size?ArrangeOverride(Size?finalSize)
????????{
????????????var?offset?=?THUMB_SIZE?/?2;
????????????var?sz?=?new?Size(THUMB_SIZE,?THUMB_SIZE);
????????????lc.Arrange(new?Rect(new?Point(-offset,?AdornedElement.RenderSize.Height?/?2?-?offset),?sz));
????????????tl.Arrange(new?Rect(new?Point(-offset,?-offset),?sz));
????????????tc.Arrange(new?Rect(new?Point(AdornedElement.RenderSize.Width?/?2?-?offset,?-offset),?sz));
????????????tr.Arrange(new?Rect(new?Point(AdornedElement.RenderSize.Width?-?offset,?-offset),?sz));
????????????rc.Arrange(new?Rect(
????????????????new?Point(AdornedElement.RenderSize.Width?-?offset,?AdornedElement.RenderSize.Height?/?2?-?offset),
????????????????sz));
????????????br.Arrange(new?Rect(
????????????????new?Point(AdornedElement.RenderSize.Width?-?offset,?AdornedElement.RenderSize.Height?-?offset),?sz));
????????????bc.Arrange(new?Rect(
????????????????new?Point(AdornedElement.RenderSize.Width?/?2?-?offset,?AdornedElement.RenderSize.Height?-?offset),
????????????????sz));
????????????bl.Arrange(new?Rect(new?Point(-offset,?AdornedElement.RenderSize.Height?-?offset),?sz));
????????????return?finalSize;
????????}
????????private?void?Resize(FrameworkElement?frameworkElement)
????????{
????????????if?(double.IsNaN(frameworkElement.Width))
????????????????frameworkElement.Width?=?frameworkElement.RenderSize.Width;
????????????if?(double.IsNaN(frameworkElement.Height))
????????????????frameworkElement.Height?=?frameworkElement.RenderSize.Height;
????????}
????????private?Thumb?GetResizeThumb(Cursor?cur,?HorizontalAlignment?hor,?VerticalAlignment?ver)
????????{
????????????var?thumb?=?new?Thumb
????????????{
????????????????Width?=?THUMB_SIZE,
????????????????Height?=?THUMB_SIZE,
????????????????HorizontalAlignment?=?hor,
????????????????VerticalAlignment?=?ver,
????????????????Cursor?=?cur,
????????????????Template?=?new?ControlTemplate(typeof(Thumb))
????????????????{
????????????????????VisualTree?=?GetFactory(new?SolidColorBrush(Colors.White))
????????????????}
????????????};
????????????var?maxWidth?=?double.IsNaN(canvas.Width)???canvas.ActualWidth?:?canvas.Width;
????????????var?maxHeight?=?double.IsNaN(canvas.Height)???canvas.ActualHeight?:?canvas.Height;
????????????thumb.DragDelta?+=?(s,?e)?=>
????????????{
????????????????var?element?=?AdornedElement?as?FrameworkElement;
????????????????if?(element?==?null)
????????????????????return;
????????????????Resize(element);
????????????????switch?(thumb.VerticalAlignment)
????????????????{
????????????????????case?VerticalAlignment.Bottom:
????????????????????????if?(element.Height?+?e.VerticalChange?>?MINIMAL_SIZE)
????????????????????????{
????????????????????????????var?newHeight?=?element.Height?+?e.VerticalChange;
????????????????????????????var?top?=?Canvas.GetTop(element)?+?newHeight;
????????????????????????????if?(newHeight?>?0?&&?top?<=?canvas.ActualHeight)
????????????????????????????????element.Height?=?newHeight;
????????????????????????}
????????????????????????break;
????????????????????case?VerticalAlignment.Top:
????????????????????????if?(element.Height?-?e.VerticalChange?>?MINIMAL_SIZE)
????????????????????????{
????????????????????????????var?newHeight?=?element.Height?-?e.VerticalChange;
????????????????????????????var?top?=?Canvas.GetTop(element);
????????????????????????????if?(newHeight?>?0?&&?top?+?e.VerticalChange?>=?0)
????????????????????????????{
????????????????????????????????element.Height?=?newHeight;
????????????????????????????????Canvas.SetTop(element,?top?+?e.VerticalChange);
????????????????????????????}
????????????????????????}
????????????????????????break;
????????????????}
????????????????switch?(thumb.HorizontalAlignment)
????????????????{
????????????????????case?HorizontalAlignment.Left:
????????????????????????if?(element.Width?-?e.HorizontalChange?>?MINIMAL_SIZE)
????????????????????????{
????????????????????????????var?newWidth?=?element.Width?-?e.HorizontalChange;
????????????????????????????var?left?=?Canvas.GetLeft(element);
????????????????????????????if?(newWidth?>?0?&&?left?+?e.HorizontalChange?>=?0)
????????????????????????????{
????????????????????????????????element.Width?=?newWidth;
????????????????????????????????Canvas.SetLeft(element,?left?+?e.HorizontalChange);
????????????????????????????}
????????????????????????}
????????????????????????break;
????????????????????case?HorizontalAlignment.Right:
????????????????????????if?(element.Width?+?e.HorizontalChange?>?MINIMAL_SIZE)
????????????????????????{
????????????????????????????var?newWidth?=?element.Width?+?e.HorizontalChange;
????????????????????????????var?left?=?Canvas.GetLeft(element)?+?newWidth;
????????????????????????????if?(newWidth?>?0?&&?left?<=?canvas.ActualWidth)
????????????????????????????????element.Width?=?newWidth;
????????????????????????}
????????????????????????break;
????????????????}
????????????????e.Handled?=?true;
????????????};
????????????return?thumb;
????????}
????????private?FrameworkElementFactory?GetFactory(Brush?back)
????????{
????????????var?fef?=?new?FrameworkElementFactory(typeof(Ellipse));
????????????fef.SetValue(Shape.FillProperty,?back);
????????????fef.SetValue(Shape.StrokeProperty,?DrawingContextHelper.Brush);
????????????fef.SetValue(Shape.StrokeThicknessProperty,?(double)2);
????????????return?fef;
????????}
????????protected?override?Visual?GetVisualChild(int?index)
????????{
????????????return?visCollec[index];
????????}
????}
}

3）新建 CropImage.xaml 代碼如下:

<ResourceDictionary
????xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
????xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
????xmlns:controls="clr-namespace:WPFDevelopers.Controls">
????<ResourceDictionary.MergedDictionaries>
????????<ResourceDictionary?Source="Basic/ControlBasic.xaml"?/>
????</ResourceDictionary.MergedDictionaries>
????<Style
????????x:Key="WD.CropImage"
????????BasedOn="{StaticResource?WD.ControlBasicStyle}"
????????TargetType="{x:Type?controls:CropImage}">
????????<Setter?Property="Template">
????????????<Setter.Value>
????????????????<ControlTemplate?TargetType="{x:Type?controls:CropImage}">
????????????????????<Canvas?x:Name="PART_Canvas">
????????????????????????<Rectangle?x:Name="PART_RectangleLeft"?Style="{DynamicResource?WD.ScreenCutRectangleStyle}"?/>
????????????????????????<Rectangle?x:Name="PART_RectangleTop"?Style="{DynamicResource?WD.ScreenCutRectangleStyle}"?/>
????????????????????????<Rectangle?x:Name="PART_RectangleRight"?Style="{DynamicResource?WD.ScreenCutRectangleStyle}"?/>
????????????????????????<Rectangle?x:Name="PART_RectangleBottom"?Style="{DynamicResource?WD.ScreenCutRectangleStyle}"?/>
????????????????????????<Border
????????????????????????????x:Name="PART_Border"
????????????????????????????Background="Transparent"
????????????????????????????BorderBrush="{DynamicResource?WD.PrimaryNormalSolidColorBrush}"
????????????????????????????BorderThickness="2"
????????????????????????????Cursor="SizeAll"?/>
????????????????????</Canvas>
????????????????</ControlTemplate>
????????????</Setter.Value>
????????</Setter>
????</Style>
????<Style?BasedOn="{StaticResource?WD.CropImage}"?TargetType="{x:Type?controls:CropImage}"?/>
</ResourceDictionary>

4）新建 CropImageExample.xaml 代碼如下:

<UserControl
????x:Class="WPFDevelopers.Samples.ExampleViews.CropImageExample"
????xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
????xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
????xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
????xmlns:local="clr-namespace:WPFDevelopers.Samples.ExampleViews"
????xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
????xmlns:wd="https://github.com/WPFDevelopersOrg/WPFDevelopers"
????d:DesignHeight="450"
????d:DesignWidth="800"
????mc:Ignorable="d">
????????<Grid>
????????????<Grid.RowDefinitions>
????????????????<RowDefinition?Height="*"?/>
????????????????<RowDefinition?Height="Auto"?/>
????????????</Grid.RowDefinitions>
????????????<Grid.ColumnDefinitions>
????????????????<ColumnDefinition?/>
????????????????<ColumnDefinition?/>
????????????</Grid.ColumnDefinitions>
????????????<wd:CropImage
????????????????Name="MyCropImage"
????????????????Grid.Row="0"
????????????????Grid.Column="0"?/>
????????????<Image
????????????????Grid.Column="1"
????????????????Width="{Binding?CurrentRect.Width,?ElementName=MyCropImage}"
????????????????Height="{Binding?CurrentRect.Height,?ElementName=MyCropImage}"
????????????????VerticalAlignment="Center"
????????????????Source="{Binding?CurrentAreaBitmap,?ElementName=MyCropImage}"
????????????????Stretch="Uniform"?/>
????????????<StackPanel
????????????????Grid.Row="1"
????????????????Grid.ColumnSpan="2"
????????????????HorizontalAlignment="Center"
????????????????Orientation="Horizontal">
????????????????<Button
????????????????????Margin="0,20,10,20"
????????????????????Click="OnImportClickHandler"
????????????????????Content="選擇圖片"
????????????????????Style="{StaticResource?WD.PrimaryButton}"?/>
????????????????<Button
????????????????????Margin="0,20,10,20"
????????????????????Click="BtnSave_Click"
????????????????????Content="保存圖片"
????????????????????Style="{StaticResource?WD.SuccessPrimaryButton}"?/>
????????????</StackPanel>
????????</Grid>
</UserControl>

5）新建 CropImageExample.xaml.cs 代碼如下:

選擇圖片不允許大于 1M
如果選擇的圖片尺寸寬或高大于 500 ,則會修改圖片尺寸一半寬高

using?Microsoft.Win32;
using?System;
using?System.IO;
using?System.Windows;
using?System.Windows.Controls;
using?System.Windows.Media.Imaging;
namespace?WPFDevelopers.Samples.ExampleViews
{
????public?partial?class?CropImageExample?:?UserControl
????{
????????public?CropImageExample()
????????{
????????????InitializeComponent();
????????}
????????double?ConvertBytesToMB(long?bytes)
????????{
????????????return?(double)bytes?/?(1024?*?1024);
????????}
????????private?void?OnImportClickHandler(object?sender,?RoutedEventArgs?e)
????????{
????????????var?openFileDialog?=?new?OpenFileDialog();
????????????openFileDialog.Filter?=?"圖像文件(*.jpg;*.jpeg;*.png;)|*.jpg;*.jpeg;*.png;";
????????????if?(openFileDialog.ShowDialog()?==?true)
????????????{
????????????????var?fileInfo?=?new?FileInfo(openFileDialog.FileName);
????????????????var?fileSize?=?fileInfo.Length;
????????????????var?mb?=?ConvertBytesToMB(fileSize);
????????????????if?(mb?>?1)
????????????????{
????????????????????WPFDevelopers.Controls.MessageBox.Show("圖片不能大于?1M?",?"提示",?MessageBoxButton.OK,?MessageBoxImage.Error);
????????????????????return;
????????????????}
????????????????var?bitmap?=?new?BitmapImage();
????????????????bitmap.BeginInit();
????????????????bitmap.CacheOption?=?BitmapCacheOption.OnLoad;
????????????????bitmap.UriSource?=?new?Uri(openFileDialog.FileName,?UriKind.Absolute);
????????????????bitmap.EndInit();
????????????????if?(bitmap.PixelWidth?>?500?||?bitmap.PixelHeight?>?500)
????????????????{
????????????????????var?width?=?(int)(bitmap.PixelWidth?*?0.5);
????????????????????var?height?=?(int)(bitmap.PixelHeight?*?0.5);
????????????????????var?croppedBitmap?=?new?CroppedBitmap(bitmap,?new?Int32Rect(0,?0,?width,?height));
????????????????????var?bitmapNew?=?new?BitmapImage();
????????????????????bitmapNew.BeginInit();
????????????????????bitmapNew.DecodePixelWidth?=?width;
????????????????????bitmapNew.DecodePixelHeight?=?height;
????????????????????var?memoryStream?=?new?MemoryStream();
????????????????????var?encoder?=?new?JpegBitmapEncoder();
????????????????????encoder.Frames.Add(BitmapFrame.Create(croppedBitmap.Source));
????????????????????encoder.Save(memoryStream);
????????????????????memoryStream.Seek(0,?SeekOrigin.Begin);
????????????????????bitmapNew.StreamSource?=?memoryStream;
????????????????????bitmapNew.EndInit();
????????????????????MyCropImage.Source?=?bitmapNew;
????????????????}
????????????????else
????????????????{
????????????????????MyCropImage.Source?=?bitmap;
????????????????}
????????????}
????????}
????????private?void?BtnSave_Click(object?sender,?RoutedEventArgs?e)
????????{
????????????var?dlg?=?new?SaveFileDialog();
????????????dlg.FileName?=?$"WPFDevelopers_CropImage_{DateTime.Now.ToString("yyyyMMddHHmmss")}.jpg";
????????????dlg.DefaultExt?=?".jpg";
????????????dlg.Filter?=?"image?file|*.jpg";
????????????if?(dlg.ShowDialog()?==?true)
????????????{
????????????????var?pngEncoder?=?new?PngBitmapEncoder();
????????????????pngEncoder.Frames.Add(BitmapFrame.Create((BitmapSource)MyCropImage.CurrentAreaBitmap));
????????????????using?(var?fs?=?File.OpenWrite(dlg.FileName))
????????????????{
????????????????????pngEncoder.Save(fs);
????????????????????fs.Dispose();
????????????????????fs.Close();
????????????????}
????????????}
????????}
????}
}

效果圖