WPF LinearGradientBrush

Mahesh Chand
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A linear gradient brush paints an area with a linear gradient. The LinearGradientBrush object represents a linear gradient brush. The default value linear gradient value is diagonal. The StartPoint and EndPoint properties of the LinearGradientBrush represent the start and end points of a gradient. The default values of these properties is (0,0) and (1,1), which is upper-left corner to lower-right corner of an area.

Figure 16 and 17 show a diagonal gradient (MSDN sample).

Figure 16. Linear Gradient

Figure 17. Linear Gradient with Stops

Creating a Linear Gradient Brush

The LinearGradientBrush element in XAML creates a linear gradient brush. The following code snippet creates a linear gradient brush with blue and red colors by setting GradientStops. The StartPoint and EndPoint values are (0,0) and (1,1).

</LinearGradientBrush>

We can fill a shape with a gradient brush by setting a shape's Fill property to the gradient brush. The code snippet in Listing 15 creates a rectangle shape sets the Fill property to a LinearGradientBrush with blue and red colors.

<Rectangle.Fill>

</LinearGradientBrush>

</Rectangle.Fill>

</Rectangle>

Listing 15

The output looks like Figure 18.

Figure 18. A shape filled with a linear gradient brush

Now let's apply multiple stops with multiple colors. The code snippet in Listing 16 creates a linear gradient brush with five stops.

<Rectangle.Fill>

</LinearGradientBrush>

</Rectangle.Fill>

</Rectangle>

Listing 16

The new output generated by Listing 16 looks like Figure 19.

Figure 19. A linear gradient brush with 5 stops

The CreateARectangleWithLGBrush method listed in Listing 17 draws same rectangle in Figure 19 dynamically.

public void CreateARectangleWithLGBrush()

{

// Create a Rectangle

Rectangle blueRectangle = new Rectangle();

blueRectangle.Height = 100;

blueRectangle.Width = 200;

// Create a linear gradient brush with five stops

LinearGradientBrush fiveColorLGB = new LinearGradientBrush();

fiveColorLGB.StartPoint = new Point(0, 0);

fiveColorLGB.EndPoint = new Point(1, 1);

// Create and add Gradient stops

GradientStop blueGS = new GradientStop();

blueGS.Color = Colors.Blue;

blueGS.Offset = 0.0;

fiveColorLGB.GradientStops.Add(blueGS);

GradientStop orangeGS = new GradientStop();

orangeGS.Color = Colors.Orange;

orangeGS.Offset = 0.25;

fiveColorLGB.GradientStops.Add(orangeGS);

GradientStop yellowGS = new GradientStop();

yellowGS.Color = Colors.Yellow;

yellowGS.Offset = 0.50;

fiveColorLGB.GradientStops.Add(yellowGS);

GradientStop greenGS = new GradientStop();

greenGS.Color = Colors.Green;

greenGS.Offset = 0.75;

fiveColorLGB.GradientStops.Add(greenGS);

GradientStop redGS = new GradientStop();

redGS.Color = Colors.Red;

redGS.Offset = 1.0;

fiveColorLGB.GradientStops.Add(redGS);

// Set Fill property of rectangle

blueRectangle.Fill = fiveColorLGB;

// Add Rectangle to the page

LayoutRoot.Children.Add(blueRectangle);

}

Listing 17

By simply changing the StartPoint and EndPoint values, we can generate a vertical gradient shapes. By changing a few lines below in code listed in Listing 17 generates Figure 20.

// Create a linear gradient brush with five stops

LinearGradientBrush fiveColorLGB = new LinearGradientBrush();

fiveColorLGB.StartPoint = new Point(0, 0.5);

fiveColorLGB.EndPoint = new Point(1, 0.5);