Solved

C++ / MFC, rendering to a local CPaintDC and saving to file

Posted on 2015-01-05
1
272 Views
Last Modified: 2015-02-09
So, as I said in an earlier post I've been trying to write some MFC C++ code to (1) create a CPaintDC, (2) render to it, and (3) save it to file as a BMP or DIB.  And I haven't been able to get this to work, surprisingly.

The code I've cobbled together from doc and samples is below, but for some reason it just outputs a black/null square.  (I should be drawing a green square.)

Can anyone see any problems with this code?

Thanks *very* much for any help.


void CMFCApplication_TestDIBDlg::OnBnClickedButton1()
{
    CPaintDC dc(this);
    CRect rc;
    GetClientRect(rc);
    dc.FillSolidRect(rc, 0x0000FF00);  // aarrggbb ; green

    HBITMAP m_hBmp;
    LPBYTE pBits;

    BITMAPINFO bmi;
    memset(&bmi, 0, sizeof(BITMAPINFO));
    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi.bmiHeader.biWidth = rc.Width();
    bmi.bmiHeader.biHeight = -rc.Height(); // top-down
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = BI_RGB;

    m_hBmp = CreateDIBSection(dc, &bmi, DIB_RGB_COLORS, (void**)&pBits, NULL, NULL);

    CImage image;
    image.Attach(m_hBmp);
    image.Save(L"c:\\dum.bmp", Gdiplus::ImageFormatBMP);

    MessageBox(L"Done", L"debug", 0);
}

Open in new window

0
Comment
Question by:RonMexico
1 Comment
 
LVL 33

Accepted Solution

by:
sarabande earned 500 total points
ID: 40535336
the main problem of your code above is that the BITMAPINFO is sized with 1 RGBQUAD element only:

typedef struct tagBITMAPINFO {
  BITMAPINFOHEADER bmiHeader;
  RGBQUAD          bmiColors[1];
} BITMAPINFO, *PBITMAPINFO;

Open in new window


the structure is a c struct and not c++. to support dynamical bitmap sizes you need to allocate additional memory such that the bmiColors array is properly sized:

size_t sizBmiColors = rc.Width()*-rc.Height();
BITMAPINFO * pbmi = (BITMAPINFO *) new char[sizeof(BITMAPINFOHEADER) + sizBmiColors];
memset(pbmi, 0, sizeof(BITMAPINFOHEADER) + sizBmiColors);
pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
...

Open in new window


Sara
0

Featured Post

Are your AD admin tools letting you down?

Managing Active Directory can get complicated.  Often, the native tools for managing AD are just not up to the task.  The largest Active Directory installations in the world have relied on one tool to manage their day-to-day administration tasks: Hyena. Start your trial today.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This is a little timesaver I have been using for setting up Microsoft Small Business Server (SBS) in the simplest possible way. It may not be appropriate for every customer. However, when you get a situation where the person who owns the server is i…
It’s been over a month into 2017, and there is already a sophisticated Gmail phishing email making it rounds. New techniques and tactics, have given hackers a way to authentically impersonate your contacts.How it Works The attack works by targeti…
Windows 8 comes with a dramatically different user interface known as Metro. Notably missing from the new interface is a Start button and Start Menu. Many users do not like it, much preferring the interface of earlier versions — Windows 7, Windows X…
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…

803 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