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Use Transforms and Opacity Masks to Create a Reflection in WPF/E

  • 아티클

Reflections are neat. You can use them to create the illusion of depth, transforming a plain white background into a sheet of glossy white glass. In this post, I'll walk you through the process of using a ScaleTransform and an opacity mask to create a reflection in WPF/E.

You'll create a reflection for the following image.

An image of a gear, all by itself.

The following illustration shows the completed reflection.

It's that same gear again, but now it has an awesome reflection.

  1. Download the following zip file and extract it: reflection_examples.zip. From the directory where you extracted the file, navigate to the reflection_examples\reflection_example subfolder. It contains four files: aghost.js, gear_large.png, reflection.html, and reflection.xaml.

  2. Open the file named reflection.xaml. It contains the following markup.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

    <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    </Canvas>

    To run the sample, open the file named reflection.html in a browser. You should see the following output.

    A gear, without a reflection.

  3. Create a duplicate image to serve as the reflection.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <     Image Source= " gear_large.png "
    Canvas.Left= " 75 " Canvas.Top= " 20 " >
    </ Image>

    </Canvas>

  4. To flip the reflection so that it's upside down, create a ScaleTransform and set its ScaleY property to -1.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top="20">
    < Image.RenderTransform >
    <     ScaleTransformScaleY = " -1 " />
    </     Image.RenderTransform >
    </Image>

    </Canvas>

    When you run the sample, notice that the second image has been flipped almost out of sight.

    The second gear is almost totally flipped out of the canvas. You need to move it down.

  5. Move the flipped image so that it is below the original image. The most straightforward way to do this is to adjust the Canvas.Top property of the second image.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

      <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top= "258" >
    <Image.RenderTransform>
    <ScaleTransform ScaleY="-1" />
    </Image.RenderTransform>
    </Image>

    </Canvas>

    The markup now produces the following output.

    A gear with a simple reflection.

  6. Now for some finishing touches. Use an opacity mask to fade the reflected image into the background.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top="258">
    <Image.RenderTransform>
    <ScaleTransform ScaleY="-1" />
    </Image.RenderTransform>
    < Image.OpacityMask >
    <     LinearGradientBrushStartPoint = " 0.5,0.0 " EndPoint = " 0.5,1.0 " >
    <     GradientStopOffset = " 0.0 " Color = " #00000000 " />
    <     GradientStopOffset = " 1.0 " Color = " #FF000000 " />
    </     LinearGradientBrush >
    </     Image.OpacityMask >
    </Image>

    </Canvas>

    As you can see in the following output, the second image now fades into the background.

    The second gear now fades into the background.

  7. Add some distortion to the reflection by changing the ScaleY value of the ScaleTransform from -1 to -0.75.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top="258">
    <Image.RenderTransform>
    <ScaleTransform ScaleY = " -0.75" />
    </Image.RenderTransform>
    <Image.OpacityMask>
    <LinearGradientBrush StartPoint="0.5,0.0" EndPoint="0.5,1.0">
    <GradientStop Offset="0.0" Color="#00000000" />
    <GradientStop Offset="1.0" Color="#FF000000" />
    </LinearGradientBrush>
    </Image.OpacityMask>
    </Image>

    </Canvas>

    The sample now produces the following output. Notice that the reflected image appears to have changed position.

    Now the second gear is distorted, but it's too far away from the first gear.

  8. Move the reflected image so that it is just below the original image.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top= "228" >
    <Image.RenderTransform>
    <ScaleTransform ScaleY="-0.75" />
    </Image.RenderTransform>
    <Image.OpacityMask>
    <LinearGradientBrush StartPoint="0.5,0.0" EndPoint="0.5,1.0">
    <GradientStop Offset="0.0" Color="#00000000" />
    <GradientStop Offset="1.0" Color="#FF000000" />
    </LinearGradientBrush>
    </Image.OpacityMask>
    </Image>

    </Canvas>

    As you can see in the following output, the reflected image is now in the correct position.

    The gear, with a suitably distorted reflection.

  9. For the final finishing touch, make the reflection fade into the background a little bit more by setting its opacity to 0.75.

    XAML (reflection.xaml)

    <Canvas
      xmlns="https://schemas.microsoft.com/client/2007"
      xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">

      <!-- The object to reflect. -->
    <Image Source="gear_large.png"
        Canvas.Left="75" Canvas.Top="20">
    </Image>

    <!-- The reflection. -->
    <Image Source="gear_large.png"
    Canvas.Left="75" Canvas.Top="228"
    Opacity= "0.75" >
    <Image.RenderTransform>
    <ScaleTransform ScaleY="-0.75" />
    </Image.RenderTransform>
    <Image.OpacityMask>
    <LinearGradientBrush StartPoint="0.5,0.0" EndPoint="0.5,1.0">
    <GradientStop Offset="0.0" Color="#00000000" />
    <GradientStop Offset="1.0" Color="#FF000000" />
    </LinearGradientBrush>
    </Image.OpacityMask>
    </Image>

    </Canvas>

    The following illustration shows the completed reflection.

    The gear, with a reflection.

-m jacobs  

  • Transforms Overview: Describes how to use WPF/E transforms to scale, skew, translate, and rotate objects.
  • Brushes Overview: Describes how to paint with WPF/E brush objects, such as LinearGradientBrush and RadialGradientBrush.

reflection_examples.zip

Comments

  • Anonymous
    January 09, 2007
    The good folks that created the WPF/E SDK and documentation have a blog and it is a great source of information

  • Anonymous
    January 17, 2007
    If you're doing WPF/E development, you should check out the WPF/E Developer Content Blog . On that blog

  • Anonymous
    January 18, 2007
    If you're doing WPF/E development, you should check out the WPF/E Developer Content Blog. On that blog...

  • Anonymous
    January 24, 2007
    I read a great artice about Use Transforms and Opacity Masks to Create a Reflection in WPF/E and tried

  • Anonymous
    January 24, 2007
    I have added a animation for the gears... http://weblogs.asp.net/mschwarz/archive/2007/01/24/transforms-opacity-masks-and-animation-to-create-an-animated-reflection-in-wpf-e.aspx

  • Anonymous
    January 25, 2007
    Michael Schwarz , AJAX MVP and creator of the WPF/E google group has posted about extending the SDK team's

  • Anonymous
    January 25, 2007
    First the SDK team created an article about generating reflections in WPF/E . Then today I read [via

  • Anonymous
    January 25, 2007
    As you may have read on my blog I have added an animation to the gear example from Mike Harsh. Now, the

  • Anonymous
    January 26, 2007
    After reading about Bryant's CS Module , I figured I had to try something. Since I'm running a .NET 1.1