背景渐变

<maui:ImageButton BackgroundColor="Transparent">
    <maui:ImageButton.Background>
        <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
            <GradientStop Offset="0" Color="#FFC0C0C0"></GradientStop>
            <GradientStop Offset="1" Color="#FFFFFFFF"></GradientStop>
        </LinearGradientBrush>
    </maui:ImageButton.Background>
</maui:ImageButton>

<ImageButton Source="icon_login_telephone.png"  CornerRadius="25" Padding="10"
                    HeightRequest="50" WidthRequest="50" MinimumHeightRequest="50" MinimumWidthRequest="50"
                    HorizontalOptions="Center"  
                    VerticalOptions="Center" >
                <ImageButton.Background>
                    <LinearGradientBrush EndPoint="1,0">
                        <GradientStop Color="#FFF886"
                          Offset="1.0" ></GradientStop>
                        <GradientStop Color="#F072B6"
                          Offset="0.1" ></GradientStop>
                    </LinearGradientBrush>
                </ImageButton.Background>
            </ImageButton>