CroppedBitmap.BeginInit 方法

定義

表示 CroppedBitmap 初始化開始。Signals the start of the CroppedBitmap initialization.

public:
 virtual void BeginInit();
public void BeginInit ();
abstract member BeginInit : unit -> unit
override this.BeginInit : unit -> unit
Public Sub BeginInit ()

實作

例外狀況

CroppedBitmap 目前正在起始。The CroppedBitmap is currently being initialized. 已經呼叫 BeginInit()BeginInit() has already been called.

-或--or- CroppedBitmap 已經完成初始化。The CroppedBitmap has already been initialized.

範例

下列範例示範如何CroppedBitmap BeginInit使用和EndInit方法, 初始化具有一組屬性的。The following example demonstrates how to initialize a CroppedBitmap with a set of properties by using the BeginInit and EndInit methods.

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace SDKSample
{
    public partial class CroppedBitmapExample : Page
    {
        public CroppedBitmapExample()
        {

            ///// Create a BitmapImage and set it's DecodePixelWidth to 200. Use  /////
            ///// this BitmapImage as a source for other BitmapSource objects.    /////

            BitmapImage myBitmapImage = new BitmapImage();

            // BitmapSource objects like BitmapImage can only have their properties
            // changed within a BeginInit/EndInit block.
            myBitmapImage.BeginInit();
            myBitmapImage.UriSource = new Uri(@"sampleImages/WaterLilies.jpg",UriKind.Relative);

            // To save significant application memory, set the DecodePixelWidth or  
            // DecodePixelHeight of the BitmapImage value of the image source to the desired 
            // height or width of the rendered image. If you don't do this, the application will 
            // cache the image as though it were rendered as its normal size rather then just 
            // the size that is displayed.
            // Note: In order to preserve aspect ratio, set DecodePixelWidth
            // or DecodePixelHeight but not both.
            myBitmapImage.DecodePixelWidth = 200;
            myBitmapImage.EndInit();

            ////////// Crop the BitmapSource ////////////
            // Use the BitmapImage created above as the source for a new BitmapSource object
            // which is cropped.                                               
            // Note: New BitmapSource does not cache. It is always pulled when required.

            CroppedBitmap myCroppedBitmap = new CroppedBitmap();

            // BitmapSource objects like CroppedBitmap can only have their properties
            // changed within a BeginInit/EndInit block.
            myCroppedBitmap.BeginInit();

            // Use the BitmapSource object defined above as the source for this new 
            // BitmapSource (chain the BitmapSource objects together).
            myCroppedBitmap.Source = myBitmapImage;

            // Crop the image to the rectangular area defined below. 
            // The image is cropped to 80 pixels less in width and 60 less 
            // in height then the original source.
            myCroppedBitmap.SourceRect = new Int32Rect(0,0,(int)myBitmapImage.Width-80, (int)myBitmapImage.Height-60);
            myCroppedBitmap.EndInit();

            // Create Image Element
            Image myImage = new Image();
            myImage.Width = 200;
            //set image source
            myImage.Source = myCroppedBitmap;

            // Add Image to the UI
            StackPanel myStackPanel = new StackPanel();
            myStackPanel.Children.Add(myImage);
            this.Content = myStackPanel;
        }
    }
}
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media
Imports System.Windows.Media.Imaging

Namespace SDKSample

    Class CroppedBitmapExample
        Inherits Page

        Public Sub New()

            '/// Create a BitmapImage and set it's DecodePixelWidth to 200. Use  /////
            '/// this BitmapImage as a source for other BitmapSource objects.    /////
            Dim myBitmapImage As New BitmapImage()

            ' BitmapSource objects like BitmapImage can only have their properties
            ' changed within a BeginInit/EndInit block.
            myBitmapImage.BeginInit()
            myBitmapImage.UriSource = New Uri("sampleImages/WaterLilies.jpg", UriKind.Relative)

            ' To save significant application memory, set the DecodePixelWidth or  
            ' DecodePixelHeight of the BitmapImage value of the image source to the desired 
            ' height or width of the rendered image. If you don't do this, the application will 
            ' cache the image as though it were rendered as its normal size rather then just 
            ' the size that is displayed.
            ' Note: In order to preserve aspect ratio, set DecodePixelWidth
            ' or DecodePixelHeight but not both.
            myBitmapImage.DecodePixelWidth = 200
            myBitmapImage.EndInit()

            '//////// Crop the BitmapSource ////////////
            ' Use the BitmapImage created above as the source for a new BitmapSource object
            ' which is cropped.                                               
            ' Note: New BitmapSource does not cache. It is always pulled when required.
            Dim myCroppedBitmap As New CroppedBitmap()

            ' BitmapSource objects like CroppedBitmap can only have their properties
            ' changed within a BeginInit/EndInit block.
            myCroppedBitmap.BeginInit()

            ' Use the BitmapSource object defined above as the source for this new 
            ' BitmapSource (chain the BitmapSource objects together).
            myCroppedBitmap.Source = myBitmapImage

            ' Crop the image to the rectangular area defined below. 
            ' The image is cropped to 80 pixels less in width and 60 less 
            ' in height then the original source.
            myCroppedBitmap.SourceRect = New Int32Rect(0, 0, _
                CType(myBitmapImage.Width - 80, Integer), _
                CType(myBitmapImage.Height - 60, Integer))
            myCroppedBitmap.EndInit()

            ' Create Image Element
            Dim myImage As New Image()
            myImage.Width = 200
            'set image source
            myImage.Source = myCroppedBitmap

            ' Add Image to the UI
            Dim myStackPanel As New StackPanel()
            myStackPanel.Children.Add(myImage)
            Me.Content = myStackPanel

        End Sub
    End Class
End Namespace 'ImagingSnippetGallery

備註

必須在和BeginInit EndInit呼叫之間進行屬性初始化。Property initialization must be done between BeginInit and EndInit calls. CroppedBitmap一旦初始化之後, 屬性變更就會被忽略。Once the CroppedBitmap has been initialized, property changes are ignored.

適用於

另請參閱