C / C++ / MFC

Mark Salsbery20-Oct-07 5:31

20-Oct-07 5:31

Kiran Satish wrote:
But whats the best way to draw image (our images may be very big anywhere from 512x512 to 2000x3000) ??

StretchBlt() takes a source rect and a destination rect so you can specify exactly
what you want drawn, where, and at what scale.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mark Salsbery2-Oct-07 8:40

2-Oct-07 8:40

So you have a 12x12 grid of cells and you're filling each cell with pixels right?

If so, I would...

Create a memory DC - this only needs to be done for the lifetime of the drawing,
not every time a redraw is done

Make one DIBSection, 24-bit RGB. the size of the 12 cells plus any
gaps/dividers/borders. This only needs to be (re)created if the dimensions
change.

Select the DIBSection into the memory DC.

Now you can use GDI APIs to draw any borders/dividers/etc. You may only have to
do this once as well if you're not overwriting them with data pixels.

Use the pointer to the DIBSection's pixel bits to directly write pixel values in your loops.
The "stride" (# of bytes per row) only needs to be calculated once, or whenever the
size of the DIBSection changes.

To calculate starting offset (rowpointer) in pixel data, use y*stride+x*3
Cast this pointer to an RGBTRIPLE*
For each row
Loop inserting row's pixel data (use rowpointer[x] to index)
Add stride to rowpointer
You'll find this MUCH faster than SetPixel()

After all the cells have been drawn offscreen, a single BitBlt (or StretchBlt)
call can copy the entire grid to the window.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mark Salsbery3-Oct-07 12:59

3-Oct-07 12:59

Kiran Satish wrote:
Hope this helps in understanding a lil better.

Yes! Thank you!

In that case the DIBSection can be 202x202.

The calculations I've explained previously will work.

The entire grid bitmap can then be blted to the window at whatever offset you want.

** I replied to your last message but the reply came back to me.<br />
I think we exceeded the maximum message hierarchy depth in Code Project

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Nelek27-Sep-07 21:19

Nelek

27-Sep-07 21:19

I had problems with my previous project too. If it doesn't matter you, I think it will be better if you use a View/Doc app insteads of DialogBox app. The view has more functionality than a dialog box. When I changed it, it worked 2,3 times faster with my programm.

If you centralize all datas in the document, and use different views for showing whatever you need, I think it will be faster.

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Help me to understand what I'm saying, and I'll explain it better to you

Wink | ;)

Kiran Satish1-Oct-07 10:46

Kiran Satish

1-Oct-07 10:46

I thought of implementing in Doc/View architecture, but I have soo many displays embedded into my main display, I am not sure how I can implement soo many views. Not to say the least, I am not that familiar with Doc/View implementation, any good resources on it which are simple and straight away rather than jumping from one part to another part??

thanks

Nelek2-Oct-07 10:19

Nelek

2-Oct-07 10:19

About how to jump between the views, look for messages related that I wrote. I have asked about how to create different views with different menus more than once. The last, a few days ago.

But if you think is going to be difficult for you to go clear with the Doc/View... then u should try it as you think is better for you.

Mark Salsbery9-Oct-07 6:04

9-Oct-07 6:04

Any time you select an object into a DC, you should save the
previously selected object. When you're done with the DC, select the original
object back into the DC.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Kiran Satish18-Jun-08 17:55

Kiran Satish

18-Jun-08 17:55

I need some help/advice on modifying a part of my existing code. I have this application where I use the libraries provided by one of our hardware manufacturers through which we grab a frame from a monochrome camera into a memory (BYTE*) defined/assigned to that library and it displays the captured frame into the window handle that we assign to it. But for some more processing I would like to display the captured frame using my own dc object. But how can I display a 8 bit (monochrome) data into a dc ??
-thanks

PKNT

Mark Salsbery19-Jun-08 6:40

CString to char* leads to an exception

19-Jun-08 6:40

The easiest and most flexible way to do that is to create a DIBsection and copy your pixel bits
into it. That gives you an HBITMAP you can select into DCs, and also a pointer to the pixel
bits so you can directly manipulate them.

Here's an example of the basic stuff for creating an 8bpp grayscale DIBSection:

    LONG lImageWidth = 640;
    LONG lImageHeight = 480;
    WORD wBitsPerPixel = 8;
 
    LONG lStride = (((lImageWidth * (long)wBitsPerPixel + 31L) & (~31L)) / 8L);
 
    BITMAPINFO *bm = (BITMAPINFO *)new BYTE[sizeof(BITMAPINFO) + 255 * sizeof(RGBQUAD)];

    bm->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bm->bmiHeader.biWidth = lImageWidth;
    bm->bmiHeader.biHeight = lImageHeight;
    bm->bmiHeader.biPlanes = 1;
    bm->bmiHeader.biBitCount = wBitsPerPixel;
    bm->bmiHeader.biCompression = BI_RGB;
    bm->bmiHeader.biSizeImage = 0;
    bm->bmiHeader.biXPelsPerMeter = 0;
    bm->bmiHeader.biYPelsPerMeter = 0;
    bm->bmiHeader.biClrUsed = 0;
    bm->bmiHeader.biClrImportant = 0;

    for (int color_index = 0; color_index < 256; color_index++)
    {
        bm->bmiColors[color_index].rgbBlue = color_index;
        bm->bmiColors[color_index].rgbGreen = color_index;
        bm->bmiColors[color_index].rgbRed = color_index;
        bm->bmiColors[color_index].rgbReserved = 0;
    }

    BYTE *pBitmapBits;
    HBITMAP hBitmap = ::CreateDIBSection(NULL, bm, DIB_RGB_COLORS, (void**)&pBitmapBits, NULL, 0);

    if (hBitmap)
    {
        // do something with the DIBSection

        ::DeleteObject(hBitmap);
    }

    delete[] (BYTE *)bm;

Copy your captured 8-bit pixel data to the array pointed to by pBitmapBits.

lStride is the length of each row in bytes - there may be extra bytes at the
end of each row so make sure you take that into account.

You can use hBitmap just like any DDB. You can select it into a memory DC and draw on it
with GDI functions, blt it to the screen, etc.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mike Borozdin27-Sep-07 6:41

27-Sep-07 6:41

Hello,

I'm rewriting my console application in MFC. The applications is a port scanner and it works very fine in as a console application. However, when writing it in MFC I get an unhandled exception where it isn't supposed to be.

<br />
void CNetScanMfcDlg::OnBnClickedButton1()<br />
{<br />
	//...<br />
	LPTSTR host = m_host.GetBuffer(255); //m_host is a CString variable of the Edit control value<br />
	PortScanner portScanner((char*) host, m_startPort, m_endPort);<br />
	//...<br />
}<br />
PortScanner::PortScanner(char* sHost, int startPort, int endPort) {<br />
	address.sin_family = AF_INET;<br />
	hostent* host = gethostbyname(sHost);<br />
	address.sin_addr.s_addr = (unsigned long) atoi(host->h_addr_list[0]); //this leads to an exception<br />
	this->startPort = startPort;<br />
	this->endPort = endPort;<br />
}<br />

gethostbyname() appears to return NULL, but it's not a problem with the host itself if I put gethostbyname("localhost") it works fine. I believe the string conversion causes this problem.

David Crow27-Sep-07 7:20

27-Sep-07 7:20

Since gethostbyname() expects a const char*, why are you using a char* instead? That in itself is not bad, but your use of GetBuffer() is unnecessary.

Mike Borozdin wrote:
hostent* host = gethostbyname(sHost);

What is the value of sHost at this point? If gethostbyname() is returning NULL, are you calling WSAGetLastError() to find out why?

Mike Borozdin wrote:
address.sin_addr.s_addr = (unsigned long) atoi(host->h_addr_list[0]); //this leads to an exception

Is host non-NULL at this point?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mike Borozdin27-Sep-07 7:47

27-Sep-07 7:47

The value of sHost is correct, that is if I enter "localhost" in the edit box it will be "localhost", but host is NULL, but if I put "localhost" instead of sHost it won't be NULL, so it makes me thing that there is something wrong in string conversion. Anyway I worked it out, I found a solution here. However, I'm still going to see what was wrong with my piece of code, probably I should have added a traling zero.

David Crow27-Sep-07 7:51

27-Sep-07 7:51

Mike Borozdin wrote:
Anyway I worked it out, I found a solution here.

Resulting in what change?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mike Borozdin27-Sep-07 8:09

27-Sep-07 8:09

It made it work Smile | :)

David Crow27-Sep-07 8:14

27-Sep-07 8:14

Ok, so my question was a bit ambiguous. I meant, what change was required in your code?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mike Borozdin27-Sep-07 8:43

27-Sep-07 8:43

I replaced:

<br />
LPTSTR host = m_host.GetBuffer(255); //m_host is a CString variable of the Edit control value<br />
PortScanner portScanner((char*) host, m_startPort, m_endPort);<br />

with:

<br />
size_t CharactersConverted = 0;<br />
	char host[100];<br />
	wcstombs_s(&CharactersConverted, host,  m_host.GetLength()+1, m_host, _TRUNCATE);<br />
	PortScanner portScanner(host, m_startPort, m_endPort);<br />

David Crow27-Sep-07 8:46

27-Sep-07 8:46

This looks to be a Unicode vs. ANSI issue. Which are you using?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mike Borozdin27-Sep-07 9:10

27-Sep-07 9:10

Sorry for a lame question, but how do I find out which one I'm using?

David Crow27-Sep-07 9:16

27-Sep-07 9:16

If you are using Unicode, you'll have UNICODE and _UNICODE defined either in the stdafx.h file, or in the project settings (/D).

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mike Borozdin27-Sep-07 9:30

27-Sep-07 9:30

Yes, it's UNICODE.

By the way, MessageBox((LPCTSTR) "Wrong host") shows rubbish, while MessageBox(_T("Wrong host")) works fine.

David Crow27-Sep-07 9:34

27-Sep-07 9:34

Mike Borozdin wrote:
Yes, it's UNICODE.

That might explain why gethostbyname() does not work. It's Ansi only. Try this:

void CNetScanMfcDlg::OnBnClickedButton1()
{
    PortScanner portScanner(m_host, m_startPort, m_endPort);
}
 
PortScanner::PortScanner(LPCTSTR sHost, int startPort, int endPort)
{
    address.sin_family = AF_INET;
    USES_CONVERSION;
    hostent *host = gethostbyname(T2A(sHost));
    address.sin_addr.s_addr = (unsigned long) atoi(host->h_addr_list[0]); //this leads to an exception
    this->startPort = startPort;
    this->endPort = endPort;
}

Mike Borozdin wrote:
By the way, MessageBox((LPCTSTR) "Wrong host") shows rubbish...

Since you are using Unicode, try:

MessageBox(L"Wrong host");

Using the _T() macro is the preferred method, however.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Mark Salsbery27-Sep-07 8:38

27-Sep-07 8:38

I hope making it work also included checking if host is NULL before using it...

Smile | :)

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mike Borozdin27-Sep-07 8:44