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POCapture multiple screens desktop image using Qt4
 

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    <p>i am writing a screen capture application in Qt4 with c++. I have a problem when tuning on dual screens. I am unable to get an image with the second screen. I tried a c# application and that will grab all the desktops in one image and i could extract from there each screen desktop image. Here is the c# code</p> <pre><code> using System; using System.Drawing; using System.Runtime.InteropServices; public class TestGrab { [STAThread] static void Main(string[] args) { IntPtr hDC = WindowsNative.GetDC(WindowsNative.GetDesktopWindow()); IntPtr hBitmap = WindowsNative.GetCurrentObject(hDC, WindowsNative.OBJ_BITMAP); System.Drawing.Bitmap imageDesktop = System.Drawing.Image.FromHbitmap( hBitmap); imageDesktop.Save(@"c:\zzzzdesktop.png"); } } public class WindowsNative { [DllImport("user32.dll")] public static extern IntPtr GetDesktopWindow(); [DllImport("user32.dll")] public static extern IntPtr GetDC(IntPtr ptr); public const int OBJ_BITMAP = 7; [DllImport("gdi32.dll")] public static extern IntPtr GetCurrentObject(IntPtr hdc, uint uiObjectType); } </code></pre> <p>The Qt code is smaller,also i tested if the native windows handle to the desktop is different from the Qt desktop0>winId() but them are equal</p> <pre><code>QPixmap CaptureWinDesktop() { WId desktop=GetDesktopWindow(); WId desktop2=QApplication::desktop()-&gt;winId(); if(desktop!=desktop2) { qDebug("sunt fdiferite WId"); } QPixmap entireDesktop= QPixmap::grabWindow(desktop); return entireDesktop; } </code></pre> <p>I am not sure if this is a bug in Qt or is a feature, using the same window handle it retries only the first desktop when in fact the desktop it is relay composed from the 2 screens . One idea is to use native windows calls and save the image in a temp file and load a QPixmap from there, but that is not simple to save a HBITMAP in a file in c++ without MFC. Conclusion: what do you think is that a bug in Qt? any idea how to work around it(no MFC )</p>
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    1. COAlso i found an example using GDI http://www.experts-exchange.com/Microsoft/Development/Q_26484815.html ,look at the bottom, the numbers are hard coded, so you have to get the dimensions and modify the code
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