how to save a printer hdc to image

Question

2.50/5 (2 votes)

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hello all

I want to save the printer hdc to a image file,and the hdc I get from hook the api EndPage().
the code as follow:

bool SaveToBmp(HDC hdc, RECT rc, SIZE ImgDstSize, LPCWSTR lpFilePath)
{
    bool bResult = false;
    BITMAPINFO bmpInfo = { 0 };
    BYTE *pData = NULL;
    SIZE ImgSrcSize = { rc.right - rc.left, rc.bottom - rc.top };
    HBITMAP hBmp = NULL;
    HGDIOBJ hOldObj = NULL;
    HDC hdcMem = NULL;
    //Initilaize the bitmap information   
    bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpInfo.bmiHeader.biWidth = ImgDstSize.cx;
    bmpInfo.bmiHeader.biHeight = ImgDstSize.cy;
    bmpInfo.bmiHeader.biPlanes = 1;
    bmpInfo.bmiHeader.biBitCount = 24;
    // 
    HANDLE hFile = INVALID_HANDLE_VALUE;
    BITMAPFILEHEADER bmFileHeader = { 0 };
    BITMAPINFOHEADER bmInfoHeader = { 0 };
    hdcMem = ::CreateCompatibleDC(NULL);
    if (hdcMem == NULL) {
        goto _EXIT_FUNC;
    }
    // Get the data from the memory DC 
    hBmp = CreateDIBSection(hdcMem, &bmpInfo, DIB_RGB_COLORS, reinterpret_cast<VOID **>(&pData), NULL, 0);
    if (hBmp == NULL) {
        goto _EXIT_FUNC;
    }
    // Draw to the memory DC
    hOldObj = SelectObject(hdcMem, hBmp);
    ::StretchBlt(hdcMem, 0, 0, ImgDstSize.cx, ImgDstSize.cx, hdc, rc.left, rc.top, ImgSrcSize.cx, ImgSrcSize.cy, SRCCOPY);
    DWORD dwbmpSize = ImgDstSize.cx * ImgDstSize.cy * 3;
    

    bmInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmInfoHeader.biWidth = ImgDstSize.cx;
    bmInfoHeader.biHeight = ImgDstSize.cy;
    bmInfoHeader.biPlanes = 1;
    bmInfoHeader.biBitCount = 24;
    //Bimap file header in order to write bmp file
    bmFileHeader.bfType = 0x4d42;  //bmp 
    bmFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmFileHeader.bfSize = bmFileHeader.bfOffBits + ((bmInfoHeader.biWidth * bmInfoHeader.biHeight) * 3); ///3=(24 / 8)
    hFile = CreateFile(lpFilePath,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
    if(hFile == INVALID_HANDLE_VALUE) {
        goto _EXIT_FUNC;
    }
    DWORD dwWrite = 0;
    WriteFile(hFile,&bmFileHeader,sizeof(BITMAPFILEHEADER),&dwWrite,NULL);
    WriteFile(hFile,&bmInfoHeader, sizeof(BITMAPINFOHEADER),&dwWrite,NULL);
    WriteFile(hFile,pData, dwbmpSize,&dwWrite,NULL);
    SelectObject(hdcMem, hOldObj);
    bResult = true;
_EXIT_FUNC:
    if (hBmp != NULL) {
        ::DeleteObject(hBmp);
    }
    if (hdcMem != NULL) {
        ::DeleteObject(hdcMem);
    }
    if (hFile != INVALID_HANDLE_VALUE) {
        CloseHandle(hFile); 
    }
    return bResult;
}

If I put in the hdc From the screen hdc ,the program can Get the Image,but if I put in the hdc from hook the EndPage(); the program save a error image.why

Please give me the best solution for this.

thank you!

Posted 13-Jun-11 0:53am

luama

Updated 13-Jun-11 3:50am

వేంకటనారాయణ(venkatmakam)

v2

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Comments

Sergey Alexandrovich Kryukov 13-Jun-11 13:28pm

Solution for what?!
--SA

Member 8773664 2-Apr-12 9:11am

what should be the value of rect and ImgDestSize in the arguments??

4 solutions

Solution 1

There is not point of saving HDC; you wan't be able to use it. This is a handle which is created during run-time and can be different each time. Without creating a HDC you cannot use a value of it. This would be the same as using a pointer of some random value without memory allocation of getting address of some really existing object.

The whole idea does not makes any sense. What's your ultimate goal?

—SA

Posted 13-Jun-11 7:26am

Sergey Alexandrovich Kryukov

Updated 13-Jun-11 7:28am

v2

Solution 3

Have you solved the problem ?
or use the driver instead .

Posted 14-Feb-12 19:11pm

snoozelai

Solution 4

Hi,

Did you solve this problem?

Regards,
Yuksel.

Posted 4-Dec-13 22:04pm

spartakusyuko

Comments

CHill60 5-Dec-13 7:29am

Please don't post comments as solutions - if you do this on an unanswered question you make it drop out of the list waiting for answers and fewer people will view it. Use the "Have a Question or Comment?" link next to the appropriate post.

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TRK3 · Accepted Answer · 2011-06-13T07:52:00

Solution 2

The problem probably isn't in the code you posted.

It's probably in how/when you are calling it.

I would suspect that the printer hdc may not point to what you think it's pointing to at the time you call your routine.

You don't say what the error is that you are getting. (That would be helpful in understanding the problem.)

And you don't show how you are calling this code. It's not clear what you are doing when you say "hdc from hook the EndPage()".

The Win32 function int EndPage(HDC hdc) takes an hdc as an input, it doesn't supply an hdc. Are you sure you have the right hdc?

Also, MSDN says that the EndPage function is "typically used to direct the device driver to advance to a new page". That doesn't imply anything about the state of the device context at that point. It's already been printed at that point, so it could very well be empty.

Posted 13-Jun-11 7:52am

TRK3

Comments

luama 13-Jun-11 21:35pm

thank you for you answerthe error is The Image File I Got was a Black Picture.

I Bind a dll By that code,And inject the dll into Notepad.exe,and the dll will hook the EndPage(), as:
bool EndPageHook(HDC hdc)
{
// calculate some parameters

SaveToBmp(hdc, rc, ImgDstSize, lpFilePath);

// ReSet Unhook the Func Addr
bool bResult = EndPage(hdc);

// Set Hook the Func Addr

return bResult;
}

The hdc should not be an error hdc.

TRK3 14-Jun-11 10:03am

Hmmm.... I'm not sure why you want to capture an image of something notepad would print. Why do you think you need to do that? There is probably an easier way to do whatever you are trying to do.

Also, there is no guarantee at all that the printer device context has any bitmap data associated with it at all. In fact it's a pretty good bet it doesn't. See: http://msdn.microsoft.com/en-us/library/dd162859(v=VS.85).aspx

When you print to a printer dc, whatever you do gets translated to commands to the printer -- it doesn't write to a bit map.

If you really want to do this, you'll have to hook something much earlier in the print sequence (like the CreateDC call) and provide a memDC instead of a printer dc.