从BitmapSource删除Alpha [英] Remove alpha from a BitmapSource

问题描述

我使用BitBlt()和CreateBitmapSourceFromHBitmap()将窗口捕获为BitmapSource，可以在WPF应用程序的Image元素上显示该窗口.但是由于某种原因，它捕获的大多数应用程序都是透明的.这是正在发生的事件的源图像和捕获图像:

I use BitBlt() and CreateBitmapSourceFromHBitmap() to capture a window as a BitmapSource that I can display on an Image element in a WPF application. But for some reason, most of the application that it captures is transparent. Here is a source vs. capture image of what's happening:

_{(来源: umbc.edu )}

_{(source: umbc.edu)}

它是灰色的，因为它所在的窗口的背景是灰色的.无论我给窗口提供什么背景，都将显示出来.

It's gray because the background of the window it's on is gray. Whatever background I give the window will show through.

如何获取拍摄的图像以更准确地反映原始图像?

How can I get the captured image to more accurately reflect the original?

推荐答案

代码中的问题可能是由于您使用的Win32 API(CreateCompatibleDC，SelectObject，CreateBitmap ...)引起的.我尝试了一个简单的代码，仅使用GetDC和BitBlt，它对我来说很好用.这是我的代码:

The problem in your code could be due to the Win32 API you're using (CreateCompatibleDC, SelectObject, CreateBitmap...). I tried with a simpler code, using only GetDC and BitBlt, and it works fine for me. Here's my code:

    public static Bitmap Capture(IntPtr hwnd)
    {
        IntPtr hDC = GetDC(hwnd);
        if (hDC != IntPtr.Zero)
        {
            Rectangle rect = GetWindowRectangle(hwnd);
            Bitmap bmp = new Bitmap(rect.Width, rect.Height);
            using (Graphics destGraphics = Graphics.FromImage(bmp))
            {
                BitBlt(
                    destGraphics.GetHdc(),
                    0,
                    0,
                    rect.Width,
                    rect.Height,
                    hDC,
                    0,
                    0,
                    TernaryRasterOperations.SRCCOPY);
            }
            return bmp;
        }
        return null;
    }

我在Windows Forms和WPF(使用Imaging.CreateBitmapSourceFromHBitmap)中进行了尝试，在两种情况下，对于相同的屏幕截图(Firefox中的SO页面)，它都可以正常工作.

I tried it in Windows Forms and WPF (with Imaging.CreateBitmapSourceFromHBitmap), it works fine in both cases for the same screenshot (SO page in Firefox).

HTH，

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