DCEF3:如何获取屏幕截图 [英] DCEF3: How to get a screenshot

问题描述

如何在DCEF3中获取浏览器的屏幕截图?

How to get screenshot of browser in DCEF3?

我在没有VCL的情况下创建了这样的浏览器. TakePicture 方法仅在

I create browser like this without VCL. The TakePicture method will only work if

• 不使用调试器

• 如果使用ShowWindow

• No debugger is used

• If ShowWindow is used

var
  info: TCefWindowInfo;
  Settings: TCefBrowserSettings;
begin
  FillChar(info, SizeOf(info), 0);
  info.width := width;
  info.height := height;
  FillChar(Settings, SizeOf(TCefBrowserSettings), 0);
  Settings.Size := SizeOf(TCefBrowserSettings);
  GetSettings(Settings);
  CefBrowserHostCreateBrowser(@info, FHandler, FDefaultUrl, @settings, nil);
end;

procedure TakePicture(const Browser: ICefBrowser; Height, Width: Integer);
var
  DC: HDC;
  Bmp : TBitmap;
  Handle : HWND;
  Rect : trect;
  BarHeight : integer;
  BarLeft : integer;
begin
  Bmp := TBitmap.Create;
  Bmp.PixelFormat := pf32bit;
  Handle := Browser.Host.WindowHandle;
  ShowWindow(handle, SW_RESTORE); // will work only if this is used otherwise black image!
  BarLeft := GetSystemMetrics(SM_CXFRAME);
  BarHeight := GetSystemMetrics(SM_CYCAPTION) + GetSystemMetrics(SM_CYFRAME);
  GetWindowRect(Handle, Rect);
  DC := GetDC(Handle);
  Bmp.Width := Rect.Right - Rect.Left;
  Bmp.Height := (Rect.Bottom - Rect.Top);
  BitBlt(Bmp.Canvas.Handle, 0, 0, Bmp.Width, Bmp.Height, DC, -BarLeft, -BarHeight, SRCCOPY);
  ReleaseDC(Handle, DC);
  Bmp.SaveToFile('c:\test.bmp');
  Bmp.Free;
end;

推荐答案

这基本上是屏幕外渲染.在DCEF3的demos文件夹中，您将找到屏幕外"项目.您要查找的代码在 TChromiumOSR 的 OnPaint 事件中.它呈现为 TBitmap32 ，但是任何位图都可以使用.请注意，它已被优化为仅绘制所谓的脏"区域(自上次绘制以来已发生变化的区域)，但是如果要截屏，那不是您想要的.在我检出的存储库中，有一行注释掉了，显示了仅绘制所有内容的幼稚情况:

This is basically off-screen rendering. In the demos folder of DCEF3 you'll find a project 'offscreen'. The code you're looking for is in the OnPaint event of TChromiumOSR. It renders to a TBitmap32, but any bitmap could be made to work. Notice that it has been optimized to only paint the so-called "dirty" areas (those that have changed since last painting), but if you're making a screenshot, that's not what you want. In my check-out of the repository there's a line commented out showing the naive case of just painting everything:

SomeBitmap.SetSize(width, height);
Move(buffer^, SomeBitmap32.Bits^, width * height * 4);

我最好的猜测是魔术数字 4 代表4个字节(32位).

It's my best guess that the magic number 4 represents 4 bytes (32-bits).

我热烈推荐使用Graphics32，但是您必须使用常规的TBitmap，我将由您自己决定如何将位数组转换为像素.变暖可能会慢很多.

I warmly recommend using Graphics32 but it you have to use a regular TBitmap, I'll leave it up to you to work out how to turn the array of bits into pixels. Be warmed it will probably be a lot slower.

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