1,创建一个ViewModel类用于绑定,要支持 INotifyPropertyChanged,以便改变背景图片.
public class YourAppViewModel : INotifyPropertyChanged
{
private string imageFilePath;
private List<byte> backgroundImage;
public List<byte> BackgroundImage
{
get
{
if (this.backgroundImage == null || this.backgroundImage.Count == 0)
this.backgroundImage = new List<byte>(File.ReadAllBytes(imageFilePath));
return this.backgroundImage;
}
set
{
if (this.backgroundImage != value)
{
this.backgroundImage = null;
this.OnPropertyChanged("BackgroundImage");
}
}
}
public void ChangeBackgroundImage(string newImageFile)
{
if(this.imageFilePath != newImageFile)
{
this.imageFilePath = newImageFile;
this.BackgroundImage = null; //强制UI刷新，以获取新的图片数据。
}
}
}
还需要一个ValueConverter,负责把byte[]转换成ImageBrush.ImageSource支持的BitmapImage类型
public class ByteImageConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (targetType != typeof(ImageSource))
throw new InvalidOperationException("The target must be ImageSource or derived types");
if (value != null && value is List<Byte>)
{
List<Byte> bytes = value as List<Byte>;
if (bytes.Count > 0)
{
MemoryStream stream = new MemoryStream(bytes.ToArray());
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = stream;
image.EndInit();
return image;
}
}
return null;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
#endregion
}
在xaml中设置绑定:
<converters:ByteImageConverter x:Key="imageConverter" />
设置背景图片刷:
<ImageBrush x:Key="richTextBoxBackground"
Stretch="Fill"
ImageSource="{Binding Path=BackgroundImage,Converter={StaticResource imageConverter}}" />
绑定到RichTextBox背景上.
<RichTextBox Background="{StaticResource windowBackground}" ..../>
在你更改图片后，获取新图片的文件路径,然后调用：
YourAppViewModel.ChangeBackgroundImage(newImageFile) 方法。
