#789 – How a Scale Transform Works

A 2D scale transform in WPF is accomplished by using a transformation matrix.  The transformation matrix is multiplied by another matrix representing a single 2D point to be transformed.  The resulting matrix describes the transformed point.  When scaling a user interface element, this transformation is done individually on each point to generate the set of points representing the transformed element.

The transformation operation for scaling looks like:

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Where Sx and Sy represent the ScaleX and ScaleY properties of the ScaleTransform, respectively.

This leads to the equations:

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#788 – Flipping an Element Using a Scale Transform

You can flip any GUI element, either horizontally or vertically, by using a scale transform.

To flip an element horizontally, you use a ScaleTransform with a ScaleX value of -1.0.  To flip an element vertically, you use a ScaleTransform with a ScaleY value of -1.0.

    <StackPanel Orientation="Vertical">
        <Label Content="Jane Austen" Background="Thistle"
               HorizontalAlignment="Center" FontSize="16" Margin="10"/>
        <Label Content="Jane Austen" Background="Thistle"
               HorizontalAlignment="Center" FontSize="16" Margin="10">
            <Label.LayoutTransform>
                <ScaleTransform ScaleX="-1.0"/>
            </Label.LayoutTransform>
        </Label>
        <Label Content="Jane Austen" Background="Thistle"
               HorizontalAlignment="Center" FontSize="16" Margin="10">
            <Label.LayoutTransform>
                <ScaleTransform ScaleY="-1.0"/>
            </Label.LayoutTransform>
        </Label>
    </StackPanel>

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#778 – Animating a Scale Transform

Here’s another example of an animation of a 2D transform.  In this case, we animate the scale of the object so that it grows larger and smaller and then repeats the behavior.  This results in a sort of pulsating button.

    <Grid>
        <Button Content="Ship via Wells, Fargo &amp; Co." HorizontalAlignment="Center" VerticalAlignment="Center"
                Padding="20,10" FontSize="16"
                RenderTransformOrigin="0.5,0.5">
            <Button.RenderTransform>
                <ScaleTransform x:Name="scaleTransform" ScaleX="0.98" ScaleY="1.02"/>
            </Button.RenderTransform>
            <Button.Triggers>
                <EventTrigger RoutedEvent="Button.Loaded">
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation Storyboard.TargetName="scaleTransform"
                                             Storyboard.TargetProperty="ScaleX"
                                             From="0.98" To="1.02" Duration="0:0:0.3"
                                             AutoReverse="True" RepeatBehavior="Forever"/>
                            <DoubleAnimation Storyboard.TargetName="scaleTransform"
                                             Storyboard.TargetProperty="ScaleY"
                                             From="0.98" To="1.02" Duration="0:0:0.3"
                                             AutoReverse="True" RepeatBehavior="Forever"/>
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger>
            </Button.Triggers>
        </Button>
    </Grid>

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#768 – Scaling Transforms

You can use a scaling transform to scale a user interface element in the X or Y dimensions.  Scaling an element increases or reduces its size.  You can specify separate scaling in the X and Y dimensions.

A value of 1.0 represents the normal (not scaled) size of the element.  Scale values larger than 1.0 increase the size of the element and values less than 1.0 decrease its size.

You specify scaling using a ScaleTransform element, setting values for the ScaleX and ScaleY properties.  If you don’t supply a scale value for one of the dimensions (X or Y), a value of 1.0 is used.

Here’s a simple example:

    <StackPanel Orientation="Vertical">
        <Button Content="Push Me" HorizontalAlignment="Center" Padding="10,5" Margin="5"/>
        <Button Content="Push Me" HorizontalAlignment="Center" Padding="10,5" Margin="5">
            <Button.LayoutTransform>
                <ScaleTransform ScaleX="2.0"/>
            </Button.LayoutTransform>
        </Button>
        <Button Content="Push Me" HorizontalAlignment="Center" Padding="10,5" Margin="5">
            <Button.LayoutTransform>
                <ScaleTransform ScaleY="2.0"/>
            </Button.LayoutTransform>
        </Button>
        <Button Content="Push Me" HorizontalAlignment="Center" Padding="10,5" Margin="5">
            <Button.LayoutTransform>
                <ScaleTransform ScaleX="0.7" ScaleY="0.7"/>
            </Button.LayoutTransform>
        </Button>
    </StackPanel>

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#479 – Using a Layout Transform on Child Elements in a Canvas

You can use a LayoutTransform on child elements of a Canvas to transform them graphically.  Specifically, you can use a RotateTransform, ScaleTransform or SkewTransform.  (Translation transforms are ignored).

    <Canvas>
        <Button Content="Hopalong Cassidy" Canvas.Left="10" Canvas.Top="10">
            <Button.LayoutTransform>
                <RotateTransform Angle="45"/>
            </Button.LayoutTransform>
        </Button>
        <Button Content="Roy Rogers" Canvas.Right="10" Canvas.Top="10">
            <Button.LayoutTransform>
                <TransformGroup>
                    <ScaleTransform ScaleX="2.0"/>
                    <RotateTransform Angle="-45"/>
                </TransformGroup>
            </Button.LayoutTransform>
        </Button>
        <Button Content="Spade Cooley" Canvas.Left="10" Canvas.Bottom="10">
            <Button.LayoutTransform>
                <SkewTransform AngleX="20"/>
            </Button.LayoutTransform>
        </Button>
    </Canvas>

#297 – Create a Mirror Image of a Control or Image

You can flip any image or control, creating a mirror image, by using a 2D scaling transformation.

A scaling transform is represented by an instance of the ScaleTransform class.  You use it to scale the visual representation of any image or control in the X or Y dimension (or both).

The ScaleX and ScaleY properties of the ScaleTransform represent the scaling factors in either dimension.  These values are normally positive, but we can use values less than zero to indicate that we also want the object flipped in the corresponding dimension.

In the example below, we scale an image to half (50%) its original size, and flip it in the X dimension.

	<StackPanel Orientation="Horizontal">
		<Image Source="NativeAmerican.jpg" Margin="10" Stretch="None"/>
		<Image Source="NativeAmerican.jpg" Margin="10" Stretch="None">
			<Image.LayoutTransform>
				<ScaleTransform ScaleX="-0.5" ScaleY="0.5"/>
			</Image.LayoutTransform>
		</Image>
	</StackPanel>