title: wpf gradient brush like the picture
body: <p><img src="https://i.stack.imgur.com/jQZrZ.png" alt="enter image description here" /></p>
  
  <p>I am trying to make a brush like the picture.
  What should I do?</p>
  <p>In System.Drawing.Color, it was done as follows.</p>
  <p><strong>C# WinForm</strong></p>
  <pre><code>Rectangle drawRc = new Rectangle(x1, y1, x2 - x1, y2 - y1);
  Color[] colors = { Color.FromArgb(255, 0, 0, 0) };
  GraphicsPath path = new GraphicsPath();
  path.AddRectangle(drawRc);
  PathGradientBrush pdb = new PathGradientBrush(path)
  {
      CenterPoint = new PointF(x2, y2),
      CenterColor = patCol,
      SurroundColors = colors
  };
  
  g.FillRectangle(pdb, drawRc);
  pdb.Dispose();
  </code></pre>
  <p><strong>wpf</strong></p>
  <pre><code>double StartX = 1.00d, StartY = 1.00d;
  var list = new List&lt;GradientStop&gt;();
  list.Add(new GradientStop(Colors.Red, 0));
  list.Add(new GradientStop(Colors.Black, 1));
                          
  var gradient = new GradientStopCollection(list);
  var brush = new RadialGradientBrush(gradients) {
      MappingMode = BrushMappingMode.RelativeToBoundingBox,
      GradientOrigin = new Point(StartX, StartY),
      RadiusX = 0.7,
      RadiusY = 0.7,
      Center = new Point(0.7,0.7)
  };
  </code></pre>