Catalog/imagecatalog/AvaloniaApp.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ImageCatalog_2.AvaloniaApp">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.ThemeDictionaries>
                <ResourceDictionary x:Key="Light">
                    <SolidColorBrush x:Key="AppWindowBackgroundBrush">#F3F5F8</SolidColorBrush>
                    <SolidColorBrush x:Key="AppSurfaceBackgroundBrush">#FFFFFF</SolidColorBrush>
                    <SolidColorBrush x:Key="AppControlBackgroundBrush">#F7F8FA</SolidColorBrush>
                    <SolidColorBrush x:Key="AppControlBackgroundBrushPointerOver">#EEF2F6</SolidColorBrush>
                    <SolidColorBrush x:Key="AppBorderBrush">#D2D8E0</SolidColorBrush>
                </ResourceDictionary>
                <ResourceDictionary x:Key="Dark">
                    <SolidColorBrush x:Key="AppWindowBackgroundBrush">#1B2027</SolidColorBrush>
                    <SolidColorBrush x:Key="AppSurfaceBackgroundBrush">#242A33</SolidColorBrush>
                    <SolidColorBrush x:Key="AppControlBackgroundBrush">#2D343F</SolidColorBrush>
                    <SolidColorBrush x:Key="AppControlBackgroundBrushPointerOver">#38414E</SolidColorBrush>
                    <SolidColorBrush x:Key="AppBorderBrush">#4B5563</SolidColorBrush>
                </ResourceDictionary>
            </ResourceDictionary.ThemeDictionaries>
        </ResourceDictionary>
    </Application.Resources>

    <Application.Styles>
        <FluentTheme DensityStyle="Compact" />

        <Style Selector="Window">
            <Setter Property="Background" Value="{DynamicResource AppWindowBackgroundBrush}" />
        </Style>

        <Style Selector="Border">
            <Setter Property="Background" Value="{DynamicResource AppSurfaceBackgroundBrush}" />
            <Setter Property="BorderBrush" Value="{DynamicResource AppBorderBrush}" />
        </Style>

        <!-- Compact default styles to reduce padding/margins for a denser UI -->
        <Style Selector="TabItem">
            <Setter Property="Padding" Value="4,2" />
            <Setter Property="Margin" Value="0" />
        </Style>

        <!-- Make tab header title text smaller and remove extra margin -->
        <Style Selector="TabItem TextBlock">
            <Setter Property="FontSize" Value="12" />
            <Setter Property="Margin" Value="0" />
            <Setter Property="VerticalAlignment" Value="Center" />
        </Style>

        <Style Selector="TabControl">
            <Setter Property="Padding" Value="0" />
            <Setter Property="Margin" Value="0" />
        </Style>

        <Style Selector="TextBox">
            <Setter Property="Padding" Value="8,4" />
            <Setter Property="Margin" Value="0" />
            <Setter Property="MinHeight" Value="30" />
            <Setter Property="Background" Value="{DynamicResource AppControlBackgroundBrush}" />
            <Setter Property="BorderBrush" Value="{DynamicResource AppBorderBrush}" />
        </Style>

        <Style Selector="Button">
            <Setter Property="Padding" Value="10,4" />
            <Setter Property="Margin" Value="0" />
            <Setter Property="MinHeight" Value="30" />
            <Setter Property="Background" Value="{DynamicResource AppControlBackgroundBrush}" />
            <Setter Property="BorderBrush" Value="{DynamicResource AppBorderBrush}" />
        </Style>

        <Style Selector="Button:pointerover">
            <Setter Property="Background" Value="{DynamicResource AppControlBackgroundBrushPointerOver}" />
        </Style>

        <Style Selector="ComboBox">
            <Setter Property="MinHeight" Value="30" />
            <Setter Property="Background" Value="{DynamicResource AppControlBackgroundBrush}" />
            <Setter Property="BorderBrush" Value="{DynamicResource AppBorderBrush}" />
        </Style>

        <Style Selector="CheckBox">
            <Setter Property="Margin" Value="0,1,0,0" />
            <Setter Property="Padding" Value="2,0" />
        </Style>

        <Style Selector="RadioButton">
            <Setter Property="Margin" Value="0,1,0,0" />
            <Setter Property="Padding" Value="2,0" />
        </Style>

        <Style Selector="TextBlock">
            <Setter Property="Margin" Value="0,4,0,0" />
        </Style>

        <Style Selector="StackPanel">
            <Setter Property="Spacing" Value="4" />
        </Style>

        <Style Selector="ProgressBar">
            <Setter Property="MinHeight" Value="16" />
        </Style>

        <StyleInclude Source="avares://IconPacks.Avalonia/Icons.axaml"/>
        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Fluent.xaml"/>
    </Application.Styles>
</Application>