在新的sprint中發現了個問題，我們需要實現一個檔案縮圖的瀏覽器，顯示新增的圖片檔案的縮圖，並且顯示到應用程式中，顯示縮圖很簡單，不過本著精益求精（我自己都覺得自己是在裝b）的原則，需要完成下列需求:

(1) 圖片載入完畢之後不能夠再使用圖片檔案;

(2) 圖片載入完畢之後不能夠佔用大量記憶體;

(3) 圖片需要非同步載入，在圖片過多時儘可能快的讓使用者能夠看到部分圖片的縮圖

這三點功能對於我這種初學者來說有些困難，在網上差了很多老外的文章之後，發現瞭解決方案，具體思路：

(1) 在載入完畢圖片之後需要將對原有圖片的引用與例項進行Dispose，這樣能夠解決需求中的(1)於(2);

(2) 自己整合一個Image，這樣能夠自定義一個依賴項屬性，實現對ViewModel中的資料的繫結，來實現對圖片縮圖的非同步載入

載入圖片之後將圖片的引用Dispose：

/// <summary> /// Set Image.Source. /// </summary> /// <param name="image"></param> /// <param name="fileName"></param> private static void SetImageSource(System.Windows.Controls.Image image, string fileName) { if (!string.IsNullOrEmpty(fileName) && File.Exists(fileName)) { System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(fileName); int imageWidth = 0, imageHeight = 0; InitializeImageSize(sourceImage, image, out imageWidth, out imageHeight); // From: http://stackoverflow.com/questions/3923697/is-it-possible-to-modify-a-wpf-bitmapsource-in-memory-unsafely-from-another-thr Bitmap sourceBmp = new Bitmap(sourceImage, imageWidth, imageHeight); IntPtr hBitmap = sourceBmp.GetHbitmap(); BitmapSource bitmapSource = Imaging.CreateBitmapSourceFromHBitmap(hBitmap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions()); bitmapSource.Freeze(); WriteableBitmap writeableBmp = new WriteableBitmap(bitmapSource); sourceImage.Dispose(); sourceBmp.Dispose(); image.Source = writeableBmp; } } /// <summary> /// Initialize ImageSize. /// </summary> /// <param name="sourceImage"></param> /// <param name="image"></param> /// <param name="imageWidth"></param> /// <param name="imageHeight"></param> private static void InitializeImageSize(System.Drawing.Image sourceImage, System.Windows.Controls.Image image, out int imageWidth, out int imageHeight) { int width = sourceImage.Width; int height = sourceImage.Height; float aspect = (float)width / (float)height; if (image.Height != double.NaN) { imageHeight = Convert.ToInt32(image.Height); imageWidth = Convert.ToInt32(aspect * imageHeight); } else if (image.Width != double.NaN) { imageWidth = Convert.ToInt32(image.Width); imageHeight = Convert.ToInt32(image.Width / aspect); } else { imageHeight = 100; imageWidth = Convert.ToInt32(aspect * imageHeight); } }

自定義Image用於非同步載入：

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows.Controls; using System.Windows; using System.IO; using System.Drawing; using System.Windows.Interop; using System.Windows.Media.Imaging; using System.Windows.Threading; namespace ThrumbsViewer { /// <summary> /// Thrumb Image. /// </summary> public class ThrumbImage : System.Windows.Controls.Image { #region ... Variables ... /// <summary> /// Set ImageSource Handler. /// </summary> private static SetImageSourceHandler setImageSourceHandler; #endregion ... Variables ... #region ... Properties ... /// <summary> /// Gets or sets ThrumbImageSource. /// </summary> public string ThrumbImageSource { get; set; } /// <summary> /// ThrumbImageSourceProperty. /// </summary> public static DependencyProperty ThrumbImageSourceProperty = DependencyProperty.Register("ThrumbImageSource", typeof(string), typeof(System.Windows.Controls.Image), new FrameworkPropertyMetadata(new PropertyChangedCallback(OnThrumbImageSourcePropertyChanged))); #endregion ... Properties ... #region ... Methods ... /// <summary> /// OnThrumbImageSourcePropertyChanged. /// </summary> /// <param name="sender"></param> /// <param name="args"></param> private static void OnThrumbImageSourcePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) { if (sender is System.Windows.Controls.Image && args.NewValue is string) { System.Windows.Controls.Image image = sender as System.Windows.Controls.Image; string fileName = args.NewValue as string; setImageSourceHandler = new SetImageSourceHandler(SetImageSource); image.Dispatcher.BeginInvoke(setImageSourceHandler, DispatcherPriority.ApplicationIdle, new object[] { image, fileName }); } } /// <summary> /// Set Image.Source. /// </summary> /// <param name="image"></param> /// <param name="fileName"></param> private static void SetImageSource(System.Windows.Controls.Image image, string fileName) { if (!string.IsNullOrEmpty(fileName) && File.Exists(fileName)) { System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(fileName); int imageWidth = 0, imageHeight = 0; InitializeImageSize(sourceImage, image, out imageWidth, out imageHeight); // From: http://stackoverflow.com/questions/3923697/is-it-possible-to-modify-a-wpf-bitmapsource-in-memory-unsafely-from-another-thr Bitmap sourceBmp = new Bitmap(sourceImage, imageWidth, imageHeight); IntPtr hBitmap = sourceBmp.GetHbitmap(); BitmapSource bitmapSource = Imaging.CreateBitmapSourceFromHBitmap(hBitmap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions()); bitmapSource.Freeze(); WriteableBitmap writeableBmp = new WriteableBitmap(bitmapSource); sourceImage.Dispose(); sourceBmp.Dispose(); image.Source = writeableBmp; } } /// <summary> /// Initialize ImageSize. /// </summary> /// <param name="sourceImage"></param> /// <param name="image"></param> /// <param name="imageWidth"></param> /// <param name="imageHeight"></param> private static void InitializeImageSize(System.Drawing.Image sourceImage, System.Windows.Controls.Image image, out int imageWidth, out int imageHeight) { int width = sourceImage.Width; int height = sourceImage.Height; float aspect = (float)width / (float)height; if (image.Height != double.NaN) { imageHeight = Convert.ToInt32(image.Height); imageWidth = Convert.ToInt32(aspect * imageHeight); } else if (image.Width != double.NaN) { imageWidth = Convert.ToInt32(image.Width); imageHeight = Convert.ToInt32(image.Width / aspect); } else { imageHeight = 100; imageWidth = Convert.ToInt32(aspect * imageHeight); } } #endregion ... Methods ... } /// <summary> /// Set ImageSource Handler. /// </summary> /// <param name="image"></param> /// <param name="fileName"></param> public delegate void SetImageSourceHandler(System.Windows.Controls.Image image, string fileName); }

經過測試，能夠將記憶體降低為資原始檔的大小的1/10。不過只是測試程式碼，希望您能夠對大家有所幫助，呵呵。