save an image from ink canvas

问题

I am trying to save an image from ink canvas however it does not create any file after saving, this is my code

RenderTargetBitmap rtb = new RenderTargetBitmap(
    (int)canvas.Width, (int)canvas.Height, 0, 0, PixelFormats.Default);

rtb.Render(this.canvas);

JpegBitmapEncoder encoder = new JpegBitmapEncoder();

encoder.Frames.Add(BitmapFrame.Create(rtb));

using(var file = new FileStream(@"C:\test.jpg", FileMode.Create))
{
   encoder.Save(file);
}

however it does not create any file even when I change the directory. No exceptions is invoked and no errors are shown. The code just ran normally without any problem but the file meant to be generated is not there.

回答1:

try using a Save File Dialog

Here is an example code i used in my class "add signature" in vb.net

upon button click a savefile dialog box will appear, after putting a file name and pressing save, it will be save as a png image(i used pngBitmap Encoder)

This has same format with what you are using but with a save file dialog added.

btw. WPFControl.Inkcanvas1 is my inkcanvas

'buttonSaveAsClick


   'open save file dialog box
    Dim sfd As New SaveFileDialog()
    sfd.Filter = "Png Files(*.png)|*.png"

    'save file as png (render bitmap and convert/save to png)
    Dim result As Nullable(Of Boolean) = sfd.ShowDialog()
    Dim fileName As String = ""

    If result = True Then
        fileName = sfd.FileName

        Dim size As Size = New Point(750, 400) '= WPFControl.InkCanvas1.RenderSize 
        Console.WriteLine(WPFControl.InkCanvas1.RenderSize)
        Dim rtb As New RenderTargetBitmap(CInt(size.Width), CInt(size.Height), 96, 96, Windows.Media.PixelFormats.Pbgra32)
        rtb.Render(WPFControl.InkCanvas1)
        Dim png As New PngBitmapEncoder()
        png.Frames.Add(BitmapFrame.Create(rtb))
        If String.IsNullOrEmpty(fileName) = True Then
            MsgBox("Please Enter a File Name", MsgBoxStyle.Exclamation, "File Name required!")
            Exit Sub

        Else
            Console.WriteLine(sfd.FileName)
            Console.WriteLine(convertImage.ConvertImageFiletoBytes(sfd.FileName))
        End If


        Using stm As Stream = File.Create(fileName)
            png.Save(stm)

        End Using
    End If

回答2:

<Window x:Class="WpfInkCavasSaveImage.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow"  Height="1091" Width="873" WindowState="Maximized">
    <Grid Margin="0,0,0,173" >
        <Grid.RowDefinitions>
            <RowDefinition Height="1200*" />
            <RowDefinition Height="50" />
        </Grid.RowDefinitions>    
        <InkCanvas HorizontalAlignment="Stretch" Margin="1,1,1,10" x:Name="inkCanvas1" VerticalAlignment="Stretch" Width="Auto" RenderTransformOrigin="0.5,0.5" Background="LightGreen" SnapsToDevicePixels="True" IsManipulationEnabled ="True"  Grid.RowSpan="2">
            <InkCanvas.CacheMode>
                <BitmapCache/>
            </InkCanvas.CacheMode>
            <InkCanvas.DefaultDrawingAttributes>
                <DrawingAttributes Color="Black" FitToCurve="True" Height="2.0031496062992127" IgnorePressure="False" IsHighlighter="False" StylusTip="Ellipse" StylusTipTransform="Identity" Width="2.0031496062992127"/>    
            </InkCanvas.DefaultDrawingAttributes>
        </InkCanvas>
        <Button x:Name="btnSaveImage" Content="Save Ink Canvas" Height="41" Width="155" Canvas.Left="100" Canvas.Top="900"  VerticalAlignment="Top" HorizontalAlignment="Left" RenderTransformOrigin="1.417,14.6" Margin="15,93,0,-84" Background="SkyBlue" Click="btnSaveInkCanvas" Grid.Row="1" BorderBrush="{x:Null}"/>
    </Grid>

</Window>


using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.AccessControl;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfInkCavasSaveImage
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            inkCanvas1.Width = System.Windows.SystemParameters.WorkArea.Width;
            inkCanvas1.Height = System.Windows.SystemParameters.WorkArea.Height;
        }
        private void btnSaveInkCanvas(object sender, RoutedEventArgs e)
        {
            string subpath = Directory.GetCurrentDirectory();
            SaveFileDialog saveFileDialog12 = new SaveFileDialog();
            saveFileDialog12.Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif|Png File|*.png";
            saveFileDialog12.Title = "Save an Image File";
            saveFileDialog12.InitialDirectory = subpath;
            saveFileDialog12.ShowDialog();

            if (saveFileDialog12.FileName == "") return;
            subpath = saveFileDialog12.FileName.Substring(0, saveFileDialog12.FileName.Length - saveFileDialog12.SafeFileName.Length);

            RenderTargetBitmap rtb = new RenderTargetBitmap((int)inkCanvas1.Width, (int)inkCanvas1.Height, 96d, 96d, PixelFormats.Default);
            rtb.Render(inkCanvas1);
            DrawingVisual dvInk = new DrawingVisual();
            DrawingContext dcInk = dvInk.RenderOpen();
            dcInk.DrawRectangle(inkCanvas1.Background, null, new Rect(0d, 0d, inkCanvas1.Width, inkCanvas1.Height));
            foreach (System.Windows.Ink.Stroke stroke in inkCanvas1.Strokes)
            {
                stroke.Draw(dcInk);
            }
            dcInk.Close();

            FileStream fs = File.Open(saveFileDialog12.FileName, FileMode.OpenOrCreate);//save bitmap to file
            System.Windows.Media.Imaging.JpegBitmapEncoder encoder1 = new JpegBitmapEncoder();
            encoder1.Frames.Add(BitmapFrame.Create(rtb));
            encoder1.Save(fs);
            fs.Close();
        }
    }
}

来源：https://stackoverflow.com/questions/17937856/save-an-image-from-ink-canvas