c# - 打印包含图像的 WPF 视觉对象

Question

我正在尝试打印包含多个图像的 WPF 视觉对象(确切地说是 Canvas)。图像源是从转换为 BitmapSources 的 base64 字符串加载的。当 Canvas 显示在 Window 中时，2 个图像显示正确，但是当使用 PrintDialog 的 PrintVisual 方法打印时，图像显示相同。我创建了一个缩小的示例，展示了我所看到的行为。

这是我正在使用的 XAML:

<Window x:Class="ImagePrintTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:ImagePrintTest"
    mc:Ignorable="d"
    Title="MainWindow" Height="800" Width="600">
<StackPanel>
    <Button Content="Print" Click="Button_Click" />
    <Canvas x:Name="ImageCanvas">
        <Image x:Name="ImageA" Canvas.Left="50" Canvas.Top="50" Width="380" Height="56" />
        <Image x:Name="ImageB" Canvas.Left="50" Canvas.Top="150" Width="380" Height="56" />
    </Canvas>
</StackPanel>

这是背后的代码:

public partial class MainWindow : Window
{
    string ABC_DATA = @"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";
    string DEF_DATA = @"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";

    public MainWindow()
    {
        InitializeComponent();

        ImageA.Source = Convert(ABC_DATA);
        ImageB.Source = Convert(DEF_DATA);
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        PrintDialog printDialog = new PrintDialog();

        if (printDialog.ShowDialog() == true)
        {
            printDialog.PrintVisual(ImageCanvas, "image print test");
        }
    }

    public static BitmapSource Convert(string s)
    {
        byte[] bytes;
        bytes = System.Convert.FromBase64String(s);

        BitmapSource source;

        using (System.IO.MemoryStream ms = new System.IO.MemoryStream(bytes))
        {
            source = PngBitmapDecoder.Create(ms, BitmapCreateOptions.None, BitmapCacheOption.OnLoad).Frames[0];
        }

        return source;
    }
}

我假设图像源以某种方式缓存在某个地方，但我真的无法解释这种行为。谁能解释这里发生了什么？

Answer 1

当我像这样创建第二个 BitmapFrame 时，它​​对我有用:

public static BitmapSource Convert(string s)
{
    using (var ms = new MemoryStream(System.Convert.FromBase64String(s)))
    {
        return BitmapFrame.Create(
            BitmapFrame.Create(ms, BitmapCreateOptions.None, BitmapCacheOption.OnLoad));
    }
}

但是，我无法解释这种行为。

我还注意到打印似乎破坏了布局。打印后，ImageCanvas 移动到其父 StackPanel 中的位置 (0,0)。