如何将透明光标渲染到位图并保留 alpha 通道？

我使用下面的代码来渲染透明图标：

    private void button1_Click(object sender, EventArgs e)
    {
        // using LoadCursorFromFile from user32.dll
        var cursor = NativeMethods.LoadCustomCursor(@"d:\Temp\Cursors\Cursors\aero_busy.ani");

        // cursor -> bitmap
        Bitmap bitmap = new Bitmap(48, 48, PixelFormat.Format32bppArgb);
        Graphics gBitmap = Graphics.FromImage(bitmap);
        cursor.DrawStretched(gBitmap, new Rectangle(0, 0, 32, 32));

        // 1. Draw bitmap on a form canvas
        Graphics gForm = Graphics.FromHwnd(this.Handle);
        gForm.DrawImage(bitmap, 50, 50);

        // 2. Draw cursor directly to a form canvas
        cursor.Draw(gForm, new Rectangle(100, 50, 32, 32));

        cursor.Dispose();
    }

不幸的是，我无法将透明光标渲染为位图！当我将光标直接绘制到表单画布时它可以工作，但是当我将光标绘制到位图时出现问题。 任何建议都将受到高度赞赏。

您现在拥有的解决方案并不完全保留托管代码。您自己的评论表明您正在 P/InvokingLoadCursorFromFile来自 user32.dll。无论如何，使用 Win32 API 确实没什么值得担心的。

正如我在评论中提到的，您尝试执行的操作通常对 GDI+ 绘图函数有问题，就像 .NET Framework 提供的大多数函数一样。使用 GDI 可以使该任务变得更加容易。您可以使用以下代码从光标（或图标，它们基本上可以互换）创建一个尊重 Alpha 通道的位图：

[StructLayout(LayoutKind.Sequential)]    
private struct ICONINFO
{
    public bool fIcon;
    public int xHotspot;
    public int yHotspot;
    public IntPtr hbmMask;
    public IntPtr hbmColor;
}

[DllImport("user32")]
private static extern bool GetIconInfo(IntPtr hIcon, out ICONINFO pIconInfo);

[DllImport("user32.dll")]
private static extern IntPtr LoadCursorFromFile(string lpFileName);

[DllImport("gdi32.dll", SetLastError = true)]
private static extern bool DeleteObject(IntPtr hObject);

private Bitmap BitmapFromCursor(Cursor cur)
{
    ICONINFO ii;
    GetIconInfo(cur.Handle, out ii);

    Bitmap bmp = Bitmap.FromHbitmap(ii.hbmColor);
    DeleteObject(ii.hbmColor);
    DeleteObject(ii.hbmMask);

    BitmapData bmData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, bmp.PixelFormat);
    Bitmap dstBitmap = new Bitmap(bmData.Width, bmData.Height, bmData.Stride, PixelFormat.Format32bppArgb, bmData.Scan0);
    bmp.UnlockBits(bmData);

    return new Bitmap(dstBitmap);
}

private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
    //Using LoadCursorFromFile from user32.dll, get a handle to the icon
    IntPtr hCursor = LoadCursorFromFile("C:\\Windows\\Cursors\\Windows Aero\\aero_busy.ani");

    //Create a Cursor object from that handle
    Cursor cursor = new Cursor(hCursor);

    //Convert that cursor into a bitmap
    using (Bitmap cursorBitmap = BitmapFromCursor(cursor))
    {
        //Draw that cursor bitmap directly to the form canvas
        e.Graphics.DrawImage(cursorBitmap, 50, 50);
    }
}

如果此代码无法编译，请确保您已添加using的陈述System.Drawing, System.Drawing.Imaging, and System.Runtime.InteropServices。还记得接线Form1_Paint方法作为表单的处理程序Paint event.

经测试可以正常工作：