WPF中如何使用图像API进行绘制

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows;
using System.Globalization;namespace BrawDraw.Com.Test
{
class CanvasCustomPaint : Canvas
{
protected override void OnRender(DrawingContext dc)
{
base.OnRender(dc);
//画矩形
dc.DrawRectangle(Brushes.Red, new Pen(Brushes.Blue, ),
new Rect(new Point(, ), new Size(, )));
//画文字
dc.DrawText(new FormattedText("Hello, World!", CultureInfo.CurrentCulture,
FlowDirection.LeftToRight, new Typeface("Arial"), , Brushes.Orange),
new Point(,));
}
}
}

protected void SavePhoto(string fileName)
{
DrawingVisual drawingVisual = new DrawingVisual();
DrawingContext drawingContext = drawingVisual.RenderOpen();
// 画矩形
Rect rect = new Rect(new Point(, ), new Size(, ));
drawingContext.DrawRectangle(Brushes.LightBlue, (Pen)null, rect);
// 画文字
drawingContext.DrawText(
new FormattedText("Hello, world",
CultureInfo.GetCultureInfo("en-us"),
FlowDirection.LeftToRight,
new Typeface("Verdana"),
, Brushes.Black),
new Point(, )); drawingContext.Close(); // 利用RenderTargetBitmap对象，以保存图片
RenderTargetBitmap renderBitmap = new RenderTargetBitmap((int)this.Width, (int)this.Height, , , PixelFormats.Pbgra32);
renderBitmap.Render(drawingVisual); // 利用JpegBitmapEncoder，对图像进行编码，以便进行保存
JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
// 保存文件
FileStream fileStream = new FileStream(fileName, FileMode.Create, FileAccess.ReadWrite);
encoder.Save(fileStream);
// 关闭文件流
fileStream.Close();
}