Toolkit2/Toolkit.UI.Controls.Avalonia/ContentCropper/ContentCropper.axaml

<ResourceDictionary
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="using:Toolkit.UI.Controls.Avalonia">
    <ResourceDictionary.ThemeDictionaries>
        <ResourceDictionary x:Key="Light">


            <StaticResource x:Key="ContentCropperOverlayBrush" ResourceKey="SmokeFillColorDefaultBrush" />
            <StaticResource x:Key="ContentCropperInnerBorderBrush" ResourceKey="FocusStrokeColorOuter" />

        </ResourceDictionary>
        <ResourceDictionary x:Key="Dark">

            <StaticResource x:Key="ContentCropperOuterThumbBackground" ResourceKey="ControlSolidFillColorDefaultBrush" />
            <StaticResource x:Key="ContentCropperOverlayBrush" ResourceKey="SmokeFillColorDefaultBrush" />
            <StaticResource x:Key="ContentCropperInnerBorderBrush" ResourceKey="FocusStrokeColorOuter" />
        </ResourceDictionary>
    </ResourceDictionary.ThemeDictionaries>

    <x:Double x:Key="ContentCropperThumbWidth">18</x:Double>
    <x:Double x:Key="ContentCropperThumbHeight">18</x:Double>

    <Thickness x:Key="ContentCropperTopLeftThumbBorderThickness">3,3,0,0</Thickness>
    <Thickness x:Key="ContentCropperTopRightThumbBorderThickness">0,3,3,0</Thickness>
    <Thickness x:Key="ContentCropperBottomRightThumbBorderThickness">0,0,3,3</Thickness>
    <Thickness x:Key="ContentCropperBottomLeftThumbBorderThickness">3,0,0,3</Thickness>

    <ControlTheme x:Key="ContentCropperThumbStyle" TargetType="Thumb">
        <Setter Property="BorderBrush" Value="{DynamicResource ContentCropperInnerBorderBrush}" />
        <Setter Property="ClipToBounds" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate>
                    <Border
                        Background="Transparent"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </ControlTheme>

    <ControlTheme x:Key="{x:Type ContentCropper}" TargetType="ContentCropper">
        <Setter Property="Template">
            <ControlTemplate>
                <Grid>
                    <ZoomBorder
                        x:Name="ZoomBorder"
                        ClipToBounds="True"
                        PanButton="Left">
                        <ContentPresenter
                            HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                            VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                            Content="{TemplateBinding Content}"
                            ContentTemplate="{TemplateBinding ContentTemplate}" />
                    </ZoomBorder>
                    <Canvas x:Name="Canvas">
                        <Rectangle
                            x:Name="RectangleLeft"
                            Fill="{DynamicResource ContentCropperOverlayBrush}"
                            UseLayoutRounding="True" />
                        <Rectangle
                            x:Name="RectangleTop"
                            Fill="{DynamicResource ContentCropperOverlayBrush}"
                            UseLayoutRounding="True" />
                        <Rectangle
                            x:Name="RectangleRight"
                            Fill="{DynamicResource ContentCropperOverlayBrush}"
                            UseLayoutRounding="True" />
                        <Rectangle
                            x:Name="RectangleBottom"
                            Fill="{DynamicResource ContentCropperOverlayBrush}"
                            UseLayoutRounding="True" />
                        <Border
                            x:Name="Border"
                            Background="Transparent"
                            BorderBrush="{DynamicResource ContentCropperInnerBorderBrush}"
                            BorderThickness="1"
                            Cursor="SizeAll" />
                        <Thumb
                            x:Name="TopLeftButton"
                            Width="{StaticResource ContentCropperThumbWidth}"
                            Height="{StaticResource ContentCropperThumbHeight}"
                            BorderThickness="{StaticResource ContentCropperTopLeftThumbBorderThickness}"
                            Cursor="TopLeftCorner"
                            Theme="{StaticResource ContentCropperThumbStyle}" />
                        <Thumb
                            x:Name="TopRightButton"
                            Width="{StaticResource ContentCropperThumbWidth}"
                            Height="{StaticResource ContentCropperThumbHeight}"
                            BorderThickness="{StaticResource ContentCropperTopRightThumbBorderThickness}"
                            Cursor="TopRightCorner"
                            Theme="{StaticResource ContentCropperThumbStyle}" />
                        <Thumb
                            x:Name="BottomLeftButton"
                            Width="{StaticResource ContentCropperThumbWidth}"
                            Height="{StaticResource ContentCropperThumbHeight}"
                            BorderThickness="{StaticResource ContentCropperBottomLeftThumbBorderThickness}"
                            Cursor="BottomLeftCorner"
                            Theme="{StaticResource ContentCropperThumbStyle}" />
                        <Thumb
                            x:Name="BottomRightButton"
                            Width="{StaticResource ContentCropperThumbWidth}"
                            Height="{StaticResource ContentCropperThumbHeight}"
                            BorderThickness="{StaticResource ContentCropperBottomRightThumbBorderThickness}"
                            Cursor="BottomRightCorner"
                            Theme="{StaticResource ContentCropperThumbStyle}" />
                    </Canvas>
                </Grid>
            </ControlTemplate>
        </Setter>
    </ControlTheme>
</ResourceDictionary>