背景：
我正在使用一个silverlight(1.0)应用程序,动态构建美国的地图,图标和文字覆盖在特定的位置.该地图在浏览器中工作得很好,现在我需要获得静态(可打印并插入到文档/ powerpoint中)显示的地图副本.
我正在使用一个silverlight(1.0)应用程序,动态构建美国的地图,图标和文字覆盖在特定的位置.该地图在浏览器中工作得很好,现在我需要获得静态(可打印并插入到文档/ powerpoint中)显示的地图副本.
目的：
为了获得可以在powerpoint幻灯片,单词等中使用的地图的可打印副本,我选择创建一个ASP.NET HttpHandler,以在WPF的服务器端重新创建xaml,然后将WPF渲染为作为png文件返回的位图图像,以300dpi生成,以获得更好的打印质量.
问题：
这有一个很好的一个问题,我无法使图像缩放到指定的大小.我尝试了几个不同的东西,其中一些可以在注释的行中看到.我需要能够以英寸或像素指定图像的高度和宽度,我不一定关心哪些,并且为生成的位图使xaml缩放到该大小.目前,如果我使尺寸大于根画布,画布将以生成的图像的左上角以指定的大小呈现原始大小.以下是我的httphandler的重要组成部分.存储为“MyImage”的根画布的高度为600,宽度为800.我缺少获取内容以适应指定大小的内容？
我完全不了解传递到Arrange()和Measure()中的维度,因为这些代码中的一些代码是从在线示例中获取的.我也不完全明白RenderTargetBitmap的东西.任何指导将不胜感激.
Public Sub Capture(ByVal MyImage As Canvas)
' Determine the constraining scale to maintain the aspect ratio and the bounds of the image size
Dim scale As Double = Math.Min(Width / MyImage.Width,Height / MyImage.Height)
'Dim vBox As New ViewBox()
'vBox.Stretch = Stretch.Uniform
'vBox.StretchDirection = StretchDirection.Both
'vBox.Height = Height * scale * 300 / 96.0
'vBox.Width = Width * scale * 300 / 96.0
'vBox.Child = MyImage
Dim bounds As Rect = New Rect(0,MyImage.Width * scale,MyImage.Height * scale)
MyImage.Measure(New Size(Width * scale,Height * scale))
MyImage.Arrange(bounds)
'MyImage.UpdateLayout()
' Create the target bitmap
Dim rtb As RenderTargetBitmap = New RenderTargetBitmap(CInt(Width * scale * 300 / 96.0),CInt(Height * scale * 300 / 96.0),300,PixelFormats.Pbgra32)
' Render the image to the target bitmap
Dim dv As DrawingVisual = New DrawingVisual()
Using ctx As DrawingContext = dv.RenderOpen()
Dim vb As New VisualBrush(MyImage)
'Dim vb As New VisualBrush(vBox)
ctx.DrawRectangle(vb,Nothing,New Rect(New System.Windows.Point(),bounds.Size))
End Using
rtb.Render(dv)
' Encode the image in the format selected
Dim encoder As System.Windows.Media.Imaging.BitmapEncoder
Select Case Encoding.ToLower
Case "jpg"
encoder = New System.Windows.Media.Imaging.JpegBitmapEncoder()
Case "png"
encoder = New System.Windows.Media.Imaging.PngBitmapEncoder()
Case "gif"
encoder = New System.Windows.Media.Imaging.GifBitmapEncoder()
Case "bmp"
encoder = New System.Windows.Media.Imaging.BmpBitmapEncoder()
Case "tif"
encoder = New System.Windows.Media.Imaging.TiffBitmapEncoder()
Case "wmp"
encoder = New System.Windows.Media.Imaging.WmpBitmapEncoder()
End Select
encoder.Frames.Add(System.Windows.Media.Imaging.BitmapFrame.Create(rtb))
' Create the memory stream to save the encoded image.
retImageStream = New System.IO.MemoryStream()
encoder.Save(retImageStream)
retImageStream.Flush()
retImageStream.Seek(0,System.IO.SeekOrigin.Begin)
MyImage = Nothing
End Sub
解决方法
这应该足以让你开始：
private void ExportCanvas(int width,int height)
{
string path = @"c:\temp\Test.tif";
FileStream fs = new FileStream(path,FileMode.Create);
RenderTargetBitmap renderBitmap = new RenderTargetBitmap(width,height,1/300,PixelFormats.Pbgra32);
DrawingVisual visual = new DrawingVisual();
using (DrawingContext context = visual.RenderOpen())
{
VisualBrush brush = new VisualBrush(MyCanvas);
context.DrawRectangle(brush,null,new Rect(new Point(),new Size(MyCanvas.Width,MyCanvas.Height)));
}
visual.Transform = new ScaleTransform(width / MyCanvas.ActualWidth,height / MyCanvas.ActualHeight);
renderBitmap.Render(visual);
BitmapEncoder encoder = new TiffBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
encoder.Save(fs);
fs.Close();
}
