如何在 Xamarin 表单上使用 SkiaSharp 加载文件 .svg？

Question

如何在 Xamarin Forms（Android 和 iOS）上使用 SkiaSharp 加载文件 .svg。

我试过Load SVG file in Xamarin with SkiaSharp，但我无法加载它。

我尝试使用SkiaSharp.Extended 并参考他们的演示，但仍然无法加载。

我做错了吗？

请帮帮我！

Answer 1

B1> 在您的项目Xamarin forms 中创建一个文件夹Images 并将图像.svg 保存在此。确保选择 Build Action 作为“EmbeddedResource”

B2> 下载所需的库，例如： SkiaSharp、SkiaSharp.Views.Forms、SkiaSharp.Extended.Svg

B3> 在behind code，使用方法LoadSvg(xCanvasView.AutomationId)在Page的构造函数（Example：Page是ListNewConversationPage）。并声明所需的功能：

 private SKSvg svg;

        // Get file .svg to folder Images
    private static Stream GetImageStream(string svgName)
    {
        var type = typeof(ListNewConversationPage).GetTypeInfo();
        var assembly = type.Assembly;

        var abc = assembly.GetManifestResourceStream($"{assembly.GetName().Name}.Images.{svgName}");
        return abc;
    }


        private void LoadSvg(string svgName)
    {
        // create a new SVG object
        svg = new SKSvg();

        // load the SVG document from a stream
        using (var stream = GetImageStream(svgName))
            svg.Load(stream);
    }


        private void OnPageAppearing(object sender, EventArgs e)
    {
        svg = null;

        var page = (ContentPage)sender;
        LoadSvg(page.AutomationId);

        var canvas = (SKCanvasView)page.Content;
        canvas.InvalidateSurface();
    }

        private void OnPainting(object sender, SKPaintSurfaceEventArgs e)
    {
        try
        {
            var surface = e.Surface;
            var canvas = surface.Canvas;

            var width = e.Info.Width;
            var height = e.Info.Height;

            // clear the surface
            canvas.Clear(SKColors.White);

            // the page is not visible yet
            if (svg == null)
                return;

            // calculate the scaling need to fit to screen
            float scaleX = width / svg.Picture.CullRect.Width;
            float scaleY = height / svg.Picture.CullRect.Height;
            var matrix = SKMatrix.MakeScale(scaleX, scaleY);

            // draw the svg
            canvas.DrawPicture(svg.Picture, ref matrix);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex);
        }
    }

B4> 在.xaml 文件中，与.svg 一起使用图像是image_part_circle.svg

                   <forms:SKCanvasView x:Name="xCanvasView"
                                   PaintSurface="OnPainting"
                                   HorizontalOptions="FillAndExpand"
                                   VerticalOptions="FillAndExpand"
                                   BackgroundColor="Blue"
                                   AutomationId="image_part_circle.svg" />

请在SkiaSharp.Extended查看更多信息

Answer 2

以下软件包需要安装SkiaSharp.Views.Forms、SkiaSharp.Extended和SkiaSharp.Svg。从那里我创建了一个自定义 Xamarin.Forms 控件，如下所示：

    public class SvgImage : SKCanvasView
    {
        public static readonly BindableProperty SourceProperty = BindableProperty.Create(nameof(Source), typeof(string), typeof(SvgImage), default(string), propertyChanged: OnPropertyChanged);

        public string Source
        {
            get => (string)GetValue(SourceProperty);
            set => SetValue(SourceProperty, value);
        }

        public static readonly BindableProperty AssemblyNameProperty = BindableProperty.Create(nameof(AssemblyName), typeof(string), typeof(SvgImage), default(string), propertyChanged: OnPropertyChanged);

        public string AssemblyName
        {
            get => (string)GetValue(AssemblyNameProperty);
            set => SetValue(AssemblyNameProperty, value);
        }

        static void OnPropertyChanged(BindableObject bindable, object oldValue, object newValue)
        {
            var skCanvasView = bindable as SKCanvasView;
            skCanvasView?.InvalidateSurface();
        }

        protected override void OnBindingContextChanged()
        {
            base.OnBindingContextChanged();

            InvalidateSurface();
        }

        protected override void OnSizeAllocated(double width, double height)
        {
            base.OnSizeAllocated(width, height);

            InvalidateSurface();
        }

        protected override void OnPaintSurface(SKPaintSurfaceEventArgs e)
        {
            base.OnPaintSurface(e);

            try
            {
                var surface = e.Surface;
                var canvas = surface.Canvas;

                canvas.Clear();

                if (string.IsNullOrEmpty(Source) || string.IsNullOrEmpty(AssemblyName))
                    return;

                var currentAssembly = Assembly.Load(AssemblyName);
                using (var stream = currentAssembly.GetManifestResourceStream(AssemblyName + "." + Source))
                {
                    var skSvg = new SKSvg();
                    skSvg.Load(stream);

                    var skImageInfo = e.Info;
                    canvas.Translate(skImageInfo.Width / 2f, skImageInfo.Height / 2f);

                    var skRect = skSvg.ViewBox;
                    float xRatio = skImageInfo.Width / skRect.Width;
                    float yRatio = skImageInfo.Height / skRect.Height;

                    float ratio = Math.Min(xRatio, yRatio);

                    canvas.Scale(ratio);
                    canvas.Translate(-skRect.MidX, -skRect.MidY);

                    canvas.DrawPicture(skSvg.Picture);
                }
            }
            catch (Exception exc)
            {
                Console.WriteLine("OnPaintSurface Exception: " + exc);
            }
        }
    }

我确实必须指定 Svg 图像的程序集和文件夹路径才能找到图像，并且任何 Svg 图像都应设置为 EmbeddedResource。然后在 Xaml 中使用控件：

<controls:SvgImage AssemblyName="SkiaSharpSvgImage" Source="Resources.tux1.svg" />

我创建的整个开源测试项目可以在Github上查看。此外，该 repo 可能会得到改进，但那是我第一次使用 SkiaSharp Svg 图像并测试所有内容。