WPF Tip-canvas to bitmap

Transferred from: http://www.cnblogs.com/tmywu/archive/2010/09/14/1825650.html

In WPF, we can think of canvas as a canvas, with controls in the canvas as elements, and turning them into bitmap files:

The following effects

Figure 1.1

You can set the canvas's width, height, and color type to create any image you want. Real-time rendering of the styles you've set, among other effects.

This includes creating some special effects such as shadows.

WPF provides the RenderTargetBitmap class to render any container control as a bitmap.

Create a new WPF project, creating a canvas in the page, as follows:

1 <canvas x:name= "screen" width= "height=" background= "#F0CC0000" >
2 <textblock canvas.left= "canvas.top=" x:name= "Vssize" text= "Canvs convert to Pictures" ></TextBlock>
3 </Canvas>

Do the processing in CS code:

RenderTargetBitmap BMP =NewRenderTargetBitmap ( This. Screen.width, This. Screen.height, the, the, PIXELFORMATS.PBGRA32); Bmp. Render ( This.     screen); stringFile =@"c:\xxx.jpg"; stringExtension =System.IO.Path.GetExtension (file).     ToLower (); Bitmapencoder Encoder=NewJpegbitmapencoder (); Encoder.     Frames.add (Bitmapframe.create (BMP)); using(Stream stm =file.create (File)) {Encoder.    Save (STM); }

This transforms the canvas into the effect of Figure 1.1;

If you have higher clarity requirements for the generated images, you can set the Qualitylevel property of the encoder to change the JPEG quality value, or produce a higher-quality PNG image, such as

1 encoder = new Pngbitmapencoder ();

Let's change some of the properties of the canvas, place a canvas named screen in another canvas and set the offset 50, set as follows:

<Canvas>
<canvas canvas.top= "" "x:name=" screen "width=" "height=" "background=" #F0CC0000 ">
<textblock canvas.left= "canvas.top=" x:name= "Vssize" text= "Canvs convert to Pictures" ></TextBlock>
</Canvas>
</Canvas>

The background CS code does not change;

The effect is as follows:

A black block appears on the picture, and the image is placed in Photoshop to see that the offset 50 is a transparent block, proving that any attribute offsets will affect the composition of the canvas.

Then directly in the background CS file to build a canvas directly generated bitmap is it possible? As follows:

Canvas CVS = new canvas ();Cvs. Width = the; CVs. Height= $; Label lb=NewLabel (); Lb.content="Canvas converted to picture"; Canvas.settop (LB, -); Canvas.setleft (LB, $); Cvs.child.add (LB); RenderTargetBitmap BMP=NewRenderTargetBitmap (CVS). Width, CVS. Height, the, the, PIXELFORMATS.PBGRA32); Bmp.     Render (CVS); stringFile =@"c:\xxx.jpg"; stringExtension =System.IO.Path.GetExtension (file).     ToLower (); Bitmapencoder Encoder=NewJpegbitmapencoder (); Encoder.     Frames.add (Bitmapframe.create (BMP)); using(Stream stm =file.create (File)) {Encoder.    Save (STM); }

Run the code, save the image as an empty map of 700*200, indicating that the container directly in the background cannot be converted directly to the bitmap.

Workaround:

the Rendertargetbitmap.render object is a visual object, and interface elements are inherited from the visual object.

We can build a virtual canvas object, such as drawingvisual drawingvisual = new DrawingVisual ();

Based on this, the DrawingContext object is used to re-compose the objects in the canvas and its child on the drawingvisual virtual canvas, and then render drawingvisual to generate a bitmap.

Example:

Canvas CVS =NewCanvas (); CVs. Width= the; CVs. Height= $; Label lb=NewLabel (); Lb.content="Canvas converted to picture"; Canvas.settop (LB, -); Canvas.setleft (LB, $); Cvs.child.add (lb);D rawingvisual drawingvisual=Newdrawingvisual ();D rawingcontext drawingcontext=Drawingvisual.renderopen ();//Constructs a rectangleRect rect =NewRect (NewSystem.Windows.Point (0,0),NewSystem.Windows.Point (CVS). ActualWidth, CVS. ActualHeight));//Draw a rectangleDrawingcontext.drawrectangle (CVS). Background,NewSystem.Windows.Media.Pen (), rect);//Drawing TextDrawingcontext.drawtext (NewFormattedText (),NewSystem.Windows.Point (Canvas.getleft (LB), canvas.gettop (lb)));d rawingcontext.close (); RenderTargetBitmap BMP=NewRenderTargetBitmap (CVS). Width, CVS. Height, the, the, PIXELFORMATS.PBGRA32); //Render drawingvisualbmp.     Render (drawingvisual); stringFile =@"c:\xxx.jpg"; stringExtension =System.IO.Path.GetExtension (file).     ToLower (); Bitmapencoder Encoder=NewJpegbitmapencoder (); Encoder.     Frames.add (Bitmapframe.create (BMP)); using(Stream stm =file.create (File)) {Encoder.    Save (STM); }

WPF Tip-canvas to bitmap