CODEWITHSUNDEEP
c#.netwpfxamlcleartype
Tower
Tower

Reputation: 102785

Blurry text in WPF even with ClearTypeHinting enabled?

I have a grid with this template and styles in WPF/XAML:

<Setter Property="TextOptions.TextFormattingMode" Value="Display" />
<Setter Property="RenderOptions.ClearTypeHint" Value="Enabled" />
<Setter Property="Template">
    <Setter.Value>
        <ControlTemplate TargetType="{x:Type DataGridCell}">
            <Border Padding="{TemplateBinding Padding}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
                <ContentPresenter x:Name="CellContent" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" RenderOptions.ClearTypeHint="Enabled" />
            </Border>
            <ControlTemplate.Triggers>
                <Trigger Property="IsSelected" Value="True">
                    <Setter TargetName="CellContent" Property="TextOptions.TextFormattingMode" Value="Display" />
                    <Setter TargetName="CellContent" Property="RenderOptions.ClearTypeHint" Value="Enabled" />
                    <Setter TargetName="CellContent" Property="Effect">
                        <Setter.Value>
                            <DropShadowEffect ShadowDepth="2" BlurRadius="2" Color="Black" RenderingBias="Quality" />
                        </Setter.Value>
                    </Setter>
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>
    </Setter.Value>
</Setter>

The DropShadowEffect I have when you select a grid row, seems to make the text rendering blurry (gray anti-aliasing):

enter image description here

When I remove the drop shadow effect, it looks clear because it now uses ClearType and not gray sub-pixel anti-aliasing:

enter image description here

I have tried applying RenderOptions.ClearTypeHint="Enabled" to the ContentPresenter as seen above, but it does not help.

How do I force WPF to render the text that gets displayed with drop shadow effect to retain Cleartype anti-aliasing, instead of that ugly blurry gray sub-pixel anti-aliasing?

Some believe it's blurry because of the drop shadow -- this is not true. It's blurry only because ClearType is not used. This is how it looks like in Firefox when shadow AND ClearType:

enter image description here

ClearType enabled text is colorful -- but that blurry text is not, because it does not use ClearType -- it uses gray sub-pixel anti-aliasing and that's not how ClearType works: http://en.wikipedia.org/wiki/ClearType

The question is: how do I enable ClearType for this text?

Upvotes: 7

Views: 9924

Answers (6)

Justin XL
Justin XL

Reputation: 39006

How about setting TextOptions.TextFormattingMode to Display as well as RenderOptions.BitmapScalingMode to NearestNeighbor? The latter is new in WPF 3.5 SP1 and I normally use it to remove the blur. :)

<TextBlock Text="Hello world" TextOptions.TextFormattingMode="Display"
           RenderOptions.BitmapScalingMode="NearestNeighbor"
           HorizontalAlignment="Center" TextWrapping="Wrap"
           VerticalAlignment="Center" Foreground="White" FontFamily="Microsoft Sans Serif">
    <TextBlock.Effect>
        <DropShadowEffect ShadowDepth="2" BlurRadius="2" Color="Black"
                          RenderingBias="Quality"/>
    </TextBlock.Effect>
</TextBlock>

Below is how it looks like.

enter image description here

And this is how it looks like in FireFox.

enter image description here

Upvotes: 14

bbedson
bbedson

Reputation: 143

I know this post is old but if anyone is having problems with blurry text, a border drop shadow could be the culprit. I have custom panels with a drop shadow and only when the panels were placed side by side was the text blurry. I found the answer from this Why everything in WPF is blurry? post. The solution for me was ecreif's answer and not the accepted answer. Add this to your control

    UseLayoutRounding="True"
    RenderOptions.BitmapScalingMode="NearestNeighbor"
    SnapsToDevicePixels="True
    RenderOptions.ClearTypeHint="Enabled"

Upvotes: 1

Rick Brewster
Rick Brewster

Reputation: 3494

The reason this doesn't work, and the reason you won't be able to get it to work, has to do with ClearType's sensitivity to what it's rendering on top of. For ClearType to look correct it essentially needs to do per-component alpha blending. That is, a separate alpha value for red, green, and blue (normally alpha applies to all 3). What this means is that ClearType absolutely must be rendered into a bitmap that is already opaque (all alpha values are 255) (you'll notice that window title bars still have ClearType, but they use some super secret tricks to do this).

The next step to understanding this is that WPF effects first render into an off-screen bitmap, and are then combined with what's beneath (in this case, solid white, or maybe blue if it's selected).

So, the text is first rendered into a clear, transparent bitmap. Since it has no idea what will eventually be below it, it must render using grayscale instead of ClearType. Then, the effect is applied to that bitmap. Then the bitmap is drawn to where you expect it to be on-screen, and there's no chance of getting ClearType even if it's on top of a solid color with no transparency.

As a possible workaround, try using 2 copies of the text. First, apply the effect to the "lower" version of the text (by "lower" I mean it should have a lower Z-index value, and that is the case if it is "first" in the XAML). Then, draw normal text on top of it (which will get ClearType). I think this will work but I haven't tried it, and you'll probably have to experiment until you get the desired visual outcome.

Upvotes: 2

Clemens
Clemens

Reputation: 128061

What about combining the two ideas. Draw the text with DropShadowEffect, and overlay it with the same text drawn without effect, like shown in the third line here:

text

Still not perfect, and i find it a little bold. But perhaps something you could live with. The XAML:

<StackPanel Background="LightSteelBlue" RenderOptions.ClearTypeHint="Enabled" SnapsToDevicePixels="True" >
    <Grid Margin="5">
        <TextBlock Foreground="Black" Text="Here is some sample text" Margin="1"/>
        <TextBlock Foreground="White" Text="Here is some sample text"/>
    </Grid>
    <TextBlock Margin="5" Foreground="White" Text="Here is some sample text">
        <TextBlock.Effect>
            <DropShadowEffect ShadowDepth="2" BlurRadius="2" Color="Black" RenderingBias="Quality"/>
        </TextBlock.Effect>
    </TextBlock>
    <Grid Margin="5">
        <TextBlock Foreground="White" Text="Here is some sample text">
            <TextBlock.Effect>
                <DropShadowEffect ShadowDepth="2" BlurRadius="2" Color="Black" RenderingBias="Quality"/>
            </TextBlock.Effect>
        </TextBlock>
        <TextBlock Foreground="White" Text="Here is some sample text"/>
    </Grid>
</StackPanel>

Upvotes: 3

Kent Boogaart
Kent Boogaart

Reputation: 178660

To achieve a similar result without using an effect, you can render the text twice, once slightly offset from the other:

<Grid>
    <TextBlock Text="Here is some sample text" Foreground="Black" Margin="1,1,0,0"/>
    <TextBlock Text="Here is some sample text" Foreground="White"/>
</Grid>

This yields the desired result:

enter image description here

enter image description here

You could also encapsulate this into a control (called ShadowTextBlock, perhaps) so that you don't have to go repeating yourself everywhere.

Upvotes: 4

Codo
Codo

Reputation: 78825

The DropShadowEffect object cannot work with ClearType. This is stated on the MSDN page How to: Create Text with a Shadow:

These shadow effects do not go through the Windows Presentation Foundation (WPF) text rendering pipeline. As a result, ClearType is disabled when using these effects.

After all, DropShadowEffect is a bitmap effect, not a text effect.

Upvotes: 6

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