locked
How to convert stack layout into image in xamarin forms? RRS feed

  • Question

  • User123679 posted

    Hi Everyone,

    I need to convert Stack Layout into image in xamarin forms. I think we can achieve this using Dependency Service.

    May I know it in detail?

    Any help would greatly appreciated.

    Thanks Suneel Kumar Biyyapu.

    Monday, September 16, 2019 4:34 PM

Answers

  • User369979 posted

    You need to consume Custom Renderer to achieve it. Firstly, create your own StackLayout with delegate like:

    public class MyStackLayout : StackLayout
    {
        public delegate void DrawImageHandler(Action<byte[]> action);
        public DrawImageHandler OnDrawing;
    }
    

    The renderer for iOS:

    [assembly:ExportRenderer(typeof(MyStackLayout), typeof(CustomViewRenderer))]
    namespace ViewToImageDemo.iOS
    {
        public class CustomViewRenderer : ViewRenderer<StackLayout, UIView>
        {
            protected override void OnElementChanged(ElementChangedEventArgs<StackLayout> e)
            {
                base.OnElementChanged(e);
    
                if (e.NewElement != null)
                {
                    MyStackLayout layout = e.NewElement as MyStackLayout;
                    layout.OnDrawing += NewElement_OnDrawing;
                }
            }
    
            private void NewElement_OnDrawing(Action<byte[]> action)
            {
                UIGraphics.BeginImageContext(NativeView.Frame.Size);
                NativeView.DrawViewHierarchy(NativeView.Frame, true);
                var image = UIGraphics.GetImageFromCurrentImageContext();
                UIGraphics.EndImageContext();
    
                using (var imageData = image.AsPNG())
                {
                    var bytes = new byte[imageData.Length];
                    System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, bytes, 0, Convert.ToInt32(imageData.Length));
                    action(bytes);
                }
            }
        }
    }
    

    The renderer for Android:

    [assembly: ExportRenderer(typeof(MyStackLayout), typeof(CustomViewRenderer))]
    namespace ViewToImageDemo.Droid
    {
        public class CustomViewRenderer : ViewRenderer<MyStackLayout, Android.Views.View>
        {
            public CustomViewRenderer(Context context) : base(context)
            {
            }
    
            protected override void OnElementChanged(ElementChangedEventArgs<MyStackLayout> e)
            {
                base.OnElementChanged(e);
    
                if (e.NewElement != null)
                {
                    MyStackLayout layout = e.NewElement as MyStackLayout;
                    layout.OnDrawing += NewElement_OnDrawing;
                }
            }
    
            private void NewElement_OnDrawing(Action<byte[]> action)
            {
                if (this.ViewGroup != null)
                {
                    int width = ViewGroup.Width;
                    int height = ViewGroup.Height;
    
                    //create and draw the bitmap
                    Bitmap bmp = Bitmap.CreateBitmap(width, height, Bitmap.Config.Argb8888);
                    Canvas c = new Canvas(bmp);
                    ViewGroup.Draw(c);
    
                    MemoryStream stream = new MemoryStream();
                    bmp.Compress(Bitmap.CompressFormat.Png, 100, stream);
                    byte[] byteArray = stream.ToArray();
                    action(byteArray);
                }
            }
        }
    }
    

    At last, generate an image through the button click:

    private void Button_Clicked(object sender, EventArgs e)
    {
        CaptureView.OnDrawing?.Invoke((bytes) =>
        {
            MemoryStream memoryStream = new MemoryStream(bytes);
            MyImage.Source = ImageSource.FromStream(() => memoryStream);
        });
    }
    

    See the attachment for specific code.

    • Marked as answer by Anonymous Thursday, June 3, 2021 12:00 AM
    Tuesday, September 17, 2019 7:29 AM

All replies

  • User369979 posted

    You need to consume Custom Renderer to achieve it. Firstly, create your own StackLayout with delegate like:

    public class MyStackLayout : StackLayout
    {
        public delegate void DrawImageHandler(Action<byte[]> action);
        public DrawImageHandler OnDrawing;
    }
    

    The renderer for iOS:

    [assembly:ExportRenderer(typeof(MyStackLayout), typeof(CustomViewRenderer))]
    namespace ViewToImageDemo.iOS
    {
        public class CustomViewRenderer : ViewRenderer<StackLayout, UIView>
        {
            protected override void OnElementChanged(ElementChangedEventArgs<StackLayout> e)
            {
                base.OnElementChanged(e);
    
                if (e.NewElement != null)
                {
                    MyStackLayout layout = e.NewElement as MyStackLayout;
                    layout.OnDrawing += NewElement_OnDrawing;
                }
            }
    
            private void NewElement_OnDrawing(Action<byte[]> action)
            {
                UIGraphics.BeginImageContext(NativeView.Frame.Size);
                NativeView.DrawViewHierarchy(NativeView.Frame, true);
                var image = UIGraphics.GetImageFromCurrentImageContext();
                UIGraphics.EndImageContext();
    
                using (var imageData = image.AsPNG())
                {
                    var bytes = new byte[imageData.Length];
                    System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, bytes, 0, Convert.ToInt32(imageData.Length));
                    action(bytes);
                }
            }
        }
    }
    

    The renderer for Android:

    [assembly: ExportRenderer(typeof(MyStackLayout), typeof(CustomViewRenderer))]
    namespace ViewToImageDemo.Droid
    {
        public class CustomViewRenderer : ViewRenderer<MyStackLayout, Android.Views.View>
        {
            public CustomViewRenderer(Context context) : base(context)
            {
            }
    
            protected override void OnElementChanged(ElementChangedEventArgs<MyStackLayout> e)
            {
                base.OnElementChanged(e);
    
                if (e.NewElement != null)
                {
                    MyStackLayout layout = e.NewElement as MyStackLayout;
                    layout.OnDrawing += NewElement_OnDrawing;
                }
            }
    
            private void NewElement_OnDrawing(Action<byte[]> action)
            {
                if (this.ViewGroup != null)
                {
                    int width = ViewGroup.Width;
                    int height = ViewGroup.Height;
    
                    //create and draw the bitmap
                    Bitmap bmp = Bitmap.CreateBitmap(width, height, Bitmap.Config.Argb8888);
                    Canvas c = new Canvas(bmp);
                    ViewGroup.Draw(c);
    
                    MemoryStream stream = new MemoryStream();
                    bmp.Compress(Bitmap.CompressFormat.Png, 100, stream);
                    byte[] byteArray = stream.ToArray();
                    action(byteArray);
                }
            }
        }
    }
    

    At last, generate an image through the button click:

    private void Button_Clicked(object sender, EventArgs e)
    {
        CaptureView.OnDrawing?.Invoke((bytes) =>
        {
            MemoryStream memoryStream = new MemoryStream(bytes);
            MyImage.Source = ImageSource.FromStream(() => memoryStream);
        });
    }
    

    See the attachment for specific code.

    • Marked as answer by Anonymous Thursday, June 3, 2021 12:00 AM
    Tuesday, September 17, 2019 7:29 AM
  • User89714 posted

    @LandLu - Do you have equivalent code for UWP pls?

    Tuesday, September 17, 2019 9:29 AM
  • User123679 posted

    Hi @LandLu ,

    First of all, I am grateful to you.

    If I want to convert whole listview to image then what should I do?

    And I also expecting same for UWP.

    Thanks SuneelKumar Biyyapu

    Tuesday, September 17, 2019 5:43 PM