Solved

Screen capture CreateDIBSection doesn't capture LayeredWindow

Posted on 2010-09-20
9
1,995 Views
Last Modified: 2013-12-03
Hello, I am trying to capture a screen shot using this code:

...
HWND hwnd=0;
hdc = GetWindowDC(hwnd);
memdc = CreateCompatibleDC(hdc);
...
hbmp = CreateDIBSection(hdc, &bmpinfo, DIB_PAL_COLORS, &pBits, NULL, 0)
SelectObject(memdc, hbmp);
...

Open in new window


But I layered windows doesn't appear inside the shot, it is like them were invisible, only the desktop and other windows are captured.

Using "print screen" I get a full screen shot including layered window, then how can I correct that ?

Thanks
0
Comment
Question by:Greg2FS
  • 5
  • 4
9 Comments
 
LVL 33

Expert Comment

by:pgnatyuk
ID: 33715237
The code you posted does not contain BitBlt call or any other operation that will copy the pixels. It is also not clear from where to where you copy.
CreateDIBSection creates a DIB section. It does not capture any screen. Mainly, it is a way to create HBITMAP. pBits - this is the array of the pixels.
Sorry if I simplified too much.
In this EE article "Win32: Capture an image" (http://www.experts-exchange.com/A_1739.html) you can find the code that works. There is an example that takes screenshots from the desktop.
About the layered window (if your need):
Win32: Semi-Transparent Window: http://www.experts-exchange.com/A_1783.html
 (There is the screenshot as an evidence for you).
0
 

Author Comment

by:Greg2FS
ID: 33715824
Sorry I didn't know exactly what does the job of taking the screenshot, but my code was longer and it seems that the code you link does exactly the same: the screenshot is taken but my layered window is not captured...
0
 
LVL 33

Expert Comment

by:pgnatyuk
ID: 33716098
No problem.
If you need the screenshots, you need to take the code from the article:
Win32: Capture an image
http://www.experts-exchange.com/A_1739.html
 
0
 

Author Comment

by:Greg2FS
ID: 33716244
I tried this code and said it does the same thing as mine.
0
Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

 
LVL 33

Expert Comment

by:pgnatyuk
ID: 33716358
Yes. You are right. GetDC from the desktp does not help for the window with the WS_EX_LAYERED.
For a test, I took the screenshot of the layered window itself.

#include <Windows.h>



BOOL Capture(HDC, LPRECT, LPCWSTR);



int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 

                      LPWSTR lpCmdLine, int nCmdShow)

{

    HWND hWnd;

    HDC hDC;

    RECT rect;

    hWnd = FindWindow(NULL, L"Semi-Transparent Window");

    SetForegroundWindow(hWnd);

    ::GetWindowRect(hWnd, &rect);

    ScreenToClient(hWnd, (LPPOINT)&rect);

    ScreenToClient(hWnd, (LPPOINT)&rect.right);

    hDC = GetDC(hWnd);



    Capture(hDC, &rect, L"capture.bmp");

    return 0;

}



BOOL Capture(HDC hDC, LPRECT lpRect, LPCWSTR lpszFile)

{

    BITMAPINFO bmi = { 0 };



    LPBYTE pBits = NULL;

    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);

    bmi.bmiHeader.biWidth = lpRect->right - lpRect->left;

    bmi.bmiHeader.biHeight = lpRect->bottom - lpRect->top;

    bmi.bmiHeader.biPlanes = 1;

    bmi.bmiHeader.biBitCount = 32;

    bmi.bmiHeader.biCompression = BI_RGB;

    HBITMAP hBitmap = CreateDIBSection(hDC, &bmi, 

        DIB_RGB_COLORS, (LPVOID*)&pBits, NULL, 0);



    HDC hMemDC = CreateCompatibleDC(hDC);

    HGDIOBJ hOld = SelectObject(hMemDC, hBitmap);

    BitBlt(hMemDC, 0, 0, 

        lpRect->right - lpRect->left,

        lpRect->bottom - lpRect->top,

        hDC, lpRect->left, lpRect->top, SRCCOPY);

    SelectObject(hMemDC, hOld);

    DeleteDC(hMemDC);



    DWORD nImageSize = ((((bmi.bmiHeader.biWidth * 

        bmi.bmiHeader.biBitCount) 

        + 31) & ~31) >> 3) 

        * bmi.bmiHeader.biHeight;



    BITMAPFILEHEADER header = { 0 };

    header.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + 

        (DWORD)sizeof(BITMAPINFOHEADER); 

    header.bfSize = nImageSize + sizeof(BITMAPFILEHEADER) + 

        sizeof(BITMAPINFOHEADER);

    header.bfType = 0x4D42;



    HANDLE hFile = CreateFile(lpszFile, GENERIC_WRITE,

        0, NULL, CREATE_ALWAYS, 

        FILE_ATTRIBUTE_NORMAL, NULL);   



    if (hFile != INVALID_HANDLE_VALUE) 

    {

        DWORD nWritten = 0;;

        WriteFile(hFile, (LPVOID)&header, 

            sizeof(BITMAPFILEHEADER), 

            &nWritten, NULL);

        WriteFile(hFile, (LPVOID)&bmi, 

            sizeof(BITMAPINFOHEADER), 

            &nWritten, NULL);

        WriteFile(hFile, (LPVOID)pBits, nImageSize, 

            &nWritten, NULL);

        CloseHandle(hFile);

    }



    return TRUE;

}

Open in new window

0
 
LVL 33

Accepted Solution

by:
pgnatyuk earned 500 total points
ID: 33716853
It's Delphi:
http://users.telenet.be/ws36637/transparent2.html
People say to use CAPTUREBLT together with SRCCOPY in BitBlt. They also use CreateCompatibleBitmap instead of CreateDIBSection.
 
0
 

Author Closing Comment

by:Greg2FS
ID: 33716959
Yes just using SRCCOPY|CAPTUREBLT works !
0
 

Author Comment

by:Greg2FS
ID: 33716965
Thanks
0
 
LVL 33

Expert Comment

by:pgnatyuk
ID: 33716978
:)
I've already made a short example for you.
You are welcome.
 

#include <Windows.h>



BOOL Capture(HDC, LPRECT, LPCWSTR);



int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 

                      LPWSTR lpCmdLine, int nCmdShow)

{



    HWND hWnd = GetDesktopWindow();

    HDC hDC = GetDC(hWnd);



    RECT rect = { 100, 100, 500, 500 };

    HDC hDCMem = ::CreateCompatibleDC(hDC);

    HBITMAP hBitmap = ::CreateCompatibleBitmap(hDC, 500, 500);

    HBITMAP hBmpOld = (HBITMAP)::SelectObject(hDCMem, hBitmap);



    BOOL bRet = ::BitBlt(hDCMem, 0, 0, 500, 500, hDC, 100, 100, SRCCOPY | CAPTUREBLT);



    Capture(hDCMem, &rect, L"capture.bmp");



    ::SelectObject(hDCMem, hBmpOld);

    ::DeleteObject(hBitmap);

    ::DeleteDC(hDCMem);

    return 0;

}



BOOL Capture(HDC hDC, LPRECT lpRect, LPCWSTR lpszFile)

{

    BITMAPINFO bmi = { 0 };



    LPBYTE pBits = NULL;

    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);

    bmi.bmiHeader.biWidth = lpRect->right - lpRect->left;

    bmi.bmiHeader.biHeight = lpRect->bottom - lpRect->top;

    bmi.bmiHeader.biPlanes = 1;

    bmi.bmiHeader.biBitCount = 32;

    bmi.bmiHeader.biCompression = BI_RGB;

    HBITMAP hBitmap = CreateDIBSection(hDC, &bmi, 

        DIB_RGB_COLORS, (LPVOID*)&pBits, NULL, 0);



    HDC hMemDC = CreateCompatibleDC(hDC);

    HGDIOBJ hOld = SelectObject(hMemDC, hBitmap);

    BitBlt(hMemDC, 0, 0, 

        lpRect->right - lpRect->left,

        lpRect->bottom - lpRect->top,

        hDC, lpRect->left, lpRect->top, CAPTUREBLT | SRCCOPY);

    SelectObject(hMemDC, hOld);

    DeleteDC(hMemDC);



    DWORD nImageSize = ((((bmi.bmiHeader.biWidth * 

        bmi.bmiHeader.biBitCount) 

        + 31) & ~31) >> 3) 

        * bmi.bmiHeader.biHeight;



    BITMAPFILEHEADER header = { 0 };

    header.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + 

        (DWORD)sizeof(BITMAPINFOHEADER); 

    header.bfSize = nImageSize + sizeof(BITMAPFILEHEADER) + 

        sizeof(BITMAPINFOHEADER);

    header.bfType = 0x4D42;



    HANDLE hFile = CreateFile(lpszFile, GENERIC_WRITE,

        0, NULL, CREATE_ALWAYS, 

        FILE_ATTRIBUTE_NORMAL, NULL);   



    if (hFile != INVALID_HANDLE_VALUE) 

    {

        DWORD nWritten = 0;;

        WriteFile(hFile, (LPVOID)&header, 

            sizeof(BITMAPFILEHEADER), 

            &nWritten, NULL);

        WriteFile(hFile, (LPVOID)&bmi, 

            sizeof(BITMAPINFOHEADER), 

            &nWritten, NULL);

        WriteFile(hFile, (LPVOID)pBits, nImageSize, 

            &nWritten, NULL);

        CloseHandle(hFile);

    }



    return TRUE;

}

Open in new window

capture.bmp
0

Featured Post

What Security Threats Are You Missing?

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Whether you've completed a degree in computer sciences or you're a self-taught programmer, writing your first lines of code in the real world is always a challenge. Here are some of the most common pitfalls for new programmers.
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlin…

758 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now