转换HBitmap到位图保存alpha通道。

I have been searching in Google and Stack Overflow, and I cannot find a working example.

我一直在谷歌和Stack Overflow中搜索，找不到一个有效的示例。

I need to convert a HBitmap to a Managed .NET bitmap, but the following code does not preserve the alpha channel.

我需要将一个HBitmap转换为一个托管的。net位图，但是下面的代码没有保留alpha通道。

    private static Bitmap GetBitmapFromHBitmap(IntPtr nativeHBitmap)
    {
        Bitmap bmp = Bitmap.FromHbitmap(nativeHBitmap);
        return bmp;
    }

I found this answer in SO, but it does not work for me, the example preserves the transparency, however it flips my image 180º in Y axis and also rotate it 180º. I don't know why.

所以我找到了这个答案,但它不为我工作,保留了透明的例子中,然而它会翻转我的形象180ºY轴旋转180º。我不知道为什么。

This other example seems to work, but it is C++

另一个示例似乎可以工作，但它是c++

Someone has this working in C#, and very important, without memory leaks?

有人在c#中工作，非常重要，没有内存泄漏?

Thanks in advance.

提前谢谢。

---

EDIT: Regarding the comment from @Hans Passant, I use the following code to get the HBitmap (it's a shell call to get the thumbnail or icon from the OS (only Vista and Win7).

编辑:关于来自@Hans Passant的评论，我使用以下代码获取HBitmap(这是一个shell调用，从OS获取缩略图或图标(只有Vista和Win7)。

    private static IntPtr GetHBitmap(string fileName, int width, int height, ThumbnailOptions options)
    {
        IShellItem nativeShellItem;
        Guid shellItem2Guid = new Guid(IShellItem2Guid);
        int retCode = SHCreateItemFromParsingName(fileName, IntPtr.Zero, ref shellItem2Guid, out nativeShellItem);

        NativeSize nativeSize = new NativeSize();
        nativeSize.Width = width;
        nativeSize.Height = height;

        IntPtr hBitmap;
        HResult hr = ((IShellItemImageFactory)nativeShellItem).GetImage(nativeSize, options, out hBitmap);

        Marshal.ReleaseComObject(nativeShellItem);

        if (hr == HResult.Ok) return hBitmap;

        throw Marshal.GetExceptionForHR((int) hr);
    }

1 个解决方案

#1

Please take a look at Preserving the alpha channel when converting images. It seems that it is your case.

在转换图像时，请注意保存alpha通道。似乎是你的情况。