Why is my EMF in Resources being converted to a bitmap?

Question

Why does an EMF called blank.emf in Resources end up saved as a bitmap?

private void button1_Click(object sender, EventArgs e)
{
    Metafile emf = null;
    using (var ms = new MemoryStream(Properties.Resources.blank))
    {
        emf = new Metafile(ms);
    }
    emf.Save("C:\\Users\\chrisd\\Documents\\emfbitmap1.emf",
        ImageFormat.Emf);
}

emfbitmap1.emf is a bitmap, not EMF. I am suspecting it is being converted to bitmap upon retrieval from Properties.Resources. It is definitely an EMF on the file system.

How does it get form ths MemStream to the resources? How do you establish its type? — bommelding, May 22 '18 at 10:31
@bommelding The original EMF `blank.emf` was added to the project via Properties > Resources, where it was automatically assigned the name `blank`. `Properties.Resources.blank` accesses this resource. It is originally an EMF so its type should be `Metafile`. — Chris Degnen, May 22 '18 at 10:41

Chris Degnen · Answer 1 · 2018-05-22T12:23:47.717

The EMF is being converted to a bitmap by the Save operation.

An EMF can be successfully written thanks to this answer, with minor modifications.

using System.Runtime.InteropServices;

including in the class

    [DllImport("gdi32.dll")]
    internal static extern uint GetEnhMetaFileBits(IntPtr hemf,
        uint cbBuffer, byte[] lpbBuffer);

    [DllImport("gdi32.dll")]
    internal static extern bool DeleteEnhMetaFile(IntPtr hemf);

and modifying the code

private void button1_Click(object sender, EventArgs e)
{
    Metafile emf = null;
    using (var ms = new MemoryStream(Properties.Resources.blank))
    {
        emf = new Metafile(ms);
    }

    IntPtr h = emf.GetHenhmetafile();
    uint size = GetEnhMetaFileBits(h, 0, null);
    byte[] data = new byte[size];
    GetEnhMetaFileBits(h, size, data);
    using (FileStream w = File.
        Create("C:\\Users\\chrisd\\Documents\\emfbitmap1.emf"))
    {
        w.Write(data, 0, (int)size);
    }

    DeleteEnhMetaFile(h);
}

Of course, if it is not required to have the EMF in memory it can be written to disc directly. E.g.

private void button1_Click(object sender, EventArgs e)
{
    File.WriteAllBytes("C:\\Users\\chrisd\\Documents\\emfbitmap1.emf",
        Properties.Resources.blank);
}

Why is my EMF in Resources being converted to a bitmap?

1 Answers1