c# - 从剪贴板复制增强型图元文件并将其另存为图像

我正在使用下面的C#代码从剪贴板复制图像。

if (Clipboard.ContainsData(System.Windows.DataFormats.EnhancedMetafile))
{
    /* taken from http://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/a5cebe0d-eee4-4a91-88e4-88eca9974a5c/excel-copypicture-and-asve-to-enhanced-metafile*/

    var img = (System.Windows.Interop.InteropBitmap)Clipboard.GetImage();
    var bit = Clipboard.GetImage();
    var enc = new System.Windows.Media.Imaging.JpegBitmapEncoder();

    var stream = new FileStream(fileName + ".bmp", FileMode.Create);

    enc.Frames.Add(BitmapFrame.Create(bit));
    enc.Save(stream);
}

我是从here摘录的。控件确实进入if条件。 Clipboard.GetImage()返回null。有人可以建议这里出什么问题了吗？

我也尝试了以下代码片段

Metafile metafile = Clipboard.GetData(System.Windows.DataFormats.EnhancedMetafile) as Metafile;

Control control = new Control();
Graphics grfx = control.CreateGraphics();
MemoryStream ms = new MemoryStream();
IntPtr ipHdc = grfx.GetHdc();

grfx.ReleaseHdc(ipHdc);
grfx.Dispose();
grfx = Graphics.FromImage(metafile);
grfx.Dispose();

这也行不通。

最佳答案

您可以通过p/invoke使用user32.dll，如下所示:

public const uint CF_METAFILEPICT = 3;
public const uint CF_ENHMETAFILE = 14;

[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern bool OpenClipboard(IntPtr hWndNewOwner);

[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern bool CloseClipboard();

[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern IntPtr GetClipboardData(uint format);

[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern bool IsClipboardFormatAvailable(uint format);

现在，您可以读取您的图元文件:

Metafile emf = null;
if (OpenClipboard(IntPtr.Zero))
{
    if (IsClipboardFormatAvailable(CF_ENHMETAFILE))
    {
        var ptr = GetClipboardData(CF_ENHMETAFILE);
        if (!ptr.Equals(IntPtr.Zero))
            emf = new Metafile(ptr, true);
    }

    // You must close ir, or it will be locked
    CloseClipboard();
}

我最初的要求涉及对该图元文件的更多处理，因此我创建了一个MemoryStream:

using (var graphics = Graphics.FromImage(new Bitmap(1,1,PixelFormat.Format32bppArgb)))
{
    var hdc = graphics.GetHdc();
    using (var original = new MemoryStream())
    {
        using (var dummy = Graphics.FromImage(new Metafile(original, hdc)))
        {
            dummy.DrawImage(emf, 0, 0, emf.Width, emf.Height);
            dummy.Flush();
        }
        graphics.ReleaseHdc(hdc);

        // do more stuff
    }
}