Re: Magnifying image & Resetting client scrollbars? - C / C++ / MFC Discussion Boards

Re: Accessing the date from webcamera with pure C++. Is it possible? [modified]

mk_428-Feb-09 0:08

28-Feb-09 0:08

hmm... I don't have any webcamera yet 'cause I didn't need it so far. I've just been curious about this issue. I know, there are several ways to retrive data from webcamera by using some already existing libraries and APIs. So it doesn't metter what the type of camera it is. I'am new to c++ and just want to know if it's possible to access the driver or USB port which operates on that camera and retrive data from it but without using any api's and external libraries. I don't know if my idea is worth of effort, that's why ask about it. Maybe my previous question wasn't too strict, so sorry for that.

Re: Accessing the date from webcamera with pure C++. Is it possible?

ky_rerun28-Feb-09 18:26

ky_rerun

28-Feb-09 18:26

Yes you can use the WIA for many web cams other have there own API.

a programmer traped in a thugs body

Re: Accessing the date from webcamera with pure C++. Is it possible?

mk_41-Mar-09 1:26

mk_4

1-Mar-09 1:26

It's not exactly what I meant but anyway thanks.

Re: Accessing the date from webcamera with pure C++. Is it possible?

ky_rerun1-Mar-09 5:51

ky_rerun

1-Mar-09 5:51

I reread you question and yes It would be possible but you would have to write a driver and have some knowledge of how the webcam worked at a low level. I don't think in any of the modern OS you can have direct IO access. So if thats way you want to go I would download the driver development kit.

a programmer traped in a thugs body

Re: Accessing the date from webcamera with pure C++. Is it possible?

mk_41-Mar-09 8:03

mk_4

1-Mar-09 8:03

If it's the only way to do this, then I will rather look for some webcamera with it's own API. Anyway thank you for help.

Magnifying image & Resetting client scrollbars?

Kiran Satish27-Feb-09 11:10

Kiran Satish

27-Feb-09 11:10

Hi,
I would like to know how this can be done in MFC. I have a Single Doc/View MFC application in which I display images and Zoom in/out of them etc and eveyrthing works fine except for the image position. I use scroll bars position to zoom in the image and redraw them. But, now I would like to do this so that whenever I zoom in an image, I would like to keep the image center fixed, in other words, I would like to perform zoom in/out functions with respect to the center of the image being displayed in the client area and reset the scroll bar position accordingly.

At present-
I update the scroll bar sizes as soon as I change the zoom factor.

m_cs.cx = ImgWidth()*zoom_const;<br />
m_cs.cy = ImgHeight()*zoom_const;<br />
SetScrollSizes(MM_TEXT, m_cs);<br />
InvalidateRect(NULL, true);

and then in Draw() function-

if (zoom_const > 1)<br />
{<br />
 dib->Draw(&dc, true, 0,0,myRect.Width(), myRect.Height(),<br />
       sp.x/zoom_const,sp.y/zoom_const,<br />
       myRect.Width()/zoom_const,myRect.Height()/zoom_const);<br />
}<br />
else<br />
 dib->Draw(&dc, false, 0,0,myRect.Width(), myRect.Height(),sp.x,sp.y,myRect.Width(), myRect.Height());

Could someone guide me on this??

thanks in advance.

PKNT

Re: Magnifying image & Resetting client scrollbars?

Stuart Dootson27-Feb-09 20:44

Stuart Dootson

27-Feb-09 20:44

Obviously when you zoom you need to recalculate the center position.

CPoint GetNewPos(CPoint const& oldPos, CSize const& oldSize, CSize const& newSize)
{
   CPoint newPos;

   newPos.x = (LONG)(((__int64)oldPos.x * newSize.cx) / oldSize.cx);
   newPos.y = (LONG)(((__int64)oldPos.y * newSize.cy) / oldSize.cy);
   return newPos;
}

You will also need to tell the scroll bar that its position has changed (as its sizes have changed).

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Magnifying image & Resetting client scrollbars?

Kiran Satish28-Feb-09 11:55

Kiran Satish

28-Feb-09 11:55

thanks for the reply. Whats oldPos here? For example if you have an image displayed where its left top position is (0,0) when you zoom in and if you want to do it with respect to the center of the image displayed in client area, then the new position wont be (0,0), right? from your function it still return (0,0) which is not correct. Is that true or am I interpreting it in wrong way?

Here is what I tried to implement-
int x = sp.x/zoom_prev; //sp = scrollposition
int y = sp.y/zoom_prev;
int x1 = x+myRect.Width()/zoom_prev;
int y1 = y+myRect.Height()/zoom_prev;
newpos.x = x1-myRect.Width()/zoom_const;
newpos.y = y1-myRect.Height()/zoom_const;

but this is not producing correct results

PKNT

Re: Magnifying image & Resetting client scrollbars?

Stuart Dootson28-Feb-09 12:02

Stuart Dootson

28-Feb-09 12:02

oldPos would be the point you want to remain invariant - so, the center of the image.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Magnifying image & Resetting client scrollbars?

Kiran Satish26-Mar-09 6:07

Kiran Satish

26-Mar-09 6:07

I wasn't able to resolve this issue.... can some one help me on this?? I tried several different ways and everytime it doesnt seem right. I would really appreciate any help...

thanks

PKNT

How to catch a Msg in CView?

Software200727-Feb-09 9:39

Software2007

27-Feb-09 9:39

Hello,
In MFC - I would like to capture mouse clicks On Main Frame in my CView. This is how I send a Mouse Left Click:

//In CMainFrame:
if(pActiveView->IsKindOf( RUNTIME_CLASS(CRView)) ){
				   CRView *pView = (CRView*)pActiveView;
				   if (pMsg->message == WM_LBUTTONDOWN){
					   pView->SendMessage(WM_LBUTTONDOWN,MAKELPARAM(pView->m_MousePos.x,pView->m_MousePos.y), (LPARAM)0);    //Send Left Click Message to CRealView
					  }
				}

How can I receive it in my CView? Also, not sure if I got the Wparam and LParam correctly?

Thanks

sft

Re: How to catch a Msg in CView?

Stuart Dootson27-Feb-09 9:55

Stuart Dootson

27-Feb-09 9:55

Add an OnLButtonDown[^] handler to your view.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

[Message Deleted]

Software200727-Feb-09 10:06

Software2007

27-Feb-09 10:06

[Message Deleted]

Re: How to catch a Msg in CView?

Stuart Dootson27-Feb-09 10:16

Stuart Dootson

27-Feb-09 10:16

If you're sending a left mouse button message to the view, that handler should catch it.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: How to catch a Msg in CView? [modified]

Software200727-Feb-09 10:19

Software2007

27-Feb-09 10:19

Wow, you were right. Thanks a lot man.... The only problem the Point coordinates are coming back (0,0). I thought I am sending the Point correctly as WPARAM. pView->SendMessage(WM_LBUTTONDOWN,MAKELPARAM(pView->m_MousePos.x,pView->m_MousePos.y), (LPARAM)0);
Any Ideas?

Thanks

sft

modified on Friday, February 27, 2009 4:25 PM

Re: How to catch a Msg in CView?

Stuart Dootson27-Feb-09 10:48

Stuart Dootson

27-Feb-09 10:48

The same one...WM_LBUTTONDOWN messages sent by the OS are treated exactly the same as the ones you send yourself!

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Every Alternative Character is NULL while writing to a file

Neelesh K J Jain27-Feb-09 5:13

Neelesh K J Jain

27-Feb-09 5:13

Hello Everybody,
I am facing a strange problem.
Requirement: Get the length of contents of a file and modify the header present in the file to represent the length in Hexadecimal format.
Existing Code:

if( cFilePointer.Open(strFileName ,CFile::modeRead)  )
{
	strContents.Empty();
	dwRead = 0;
        // Read the contents of the file and store in the CString object.
	do
	{
		dwRead = cFilePointer.Read(cBuffer,100);
		if ( dwRead > 0)
			strContents.operator +=(cBuffer);
	}while(dwRead > 0 );

        // Retrieve the length of the string and convert to Hex decimal number
	int iTotalLength = strContents.GetLength();
	sprintf(cLengthOfString,"%4x",iTotalLength);
	for ( int iIndex = 0;iIndex<4;iIndex++)
	{
                // If the hexadecimal number is only one digit then convert the others to zero.e.g., if the length is 5, then convert to 0005
		if ( cLengthOfString[iIndex] == 32 )
			cLengthOfString[iIndex] = 48;
                // Store the length (which is in Hexa decimal format to the 6th, 7th, 8th and 9th characters of the file
		strContents.SetAt(iIndex+6,cLengthOfString[iIndex]);
	}
	cFilePointer.Close();
	int iTemp = 0;
	int iIndexOfChar = 0;
	int iFileNameLength = strFileName.GetLength();
	CString strSlash("\\");
        
        // Add the slash to escape so that strFileName will have a proper path.
	while ( iTemp < iFileNameLength)
	{
		iIndexOfChar = strFileName.Find(strSlash,iTemp);
		if ( iIndexOfChar == -1 )
			break;

		strFileName.Insert(iIndexOfChar,strSlash);
		iTemp = iIndexOfChar + 2;
	}

        //  Re-create the file with the header information modified.
	hFile = CreateFile(strFileName,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
	if ( hFile )
		cFilePointer.m_hFile = hFile;
	if(cFilePointer)
	{
		cFilePointer.Write(strContents,iTotalLength);
		cFilePointer.Close();
	}
}

Problem:

When I executing the above code, the file is having every alternative character as NULL.

Please help in the above.
Thanks in advance,
Neelesh K J Jain.

Re: Every Alternative Character is NULL while writing to a file

Stuart Dootson27-Feb-09 5:42

Stuart Dootson

27-Feb-09 5:42

Your project is a Unicode project, isn't it. That means you are writing Unicode (well, UTF-16) characters out to your file. Then, when you read with an ASCII file reader, you are reading the file as 8-bit characters, so you see the most significant byte of the UTF-16 characters as NULLs.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Every Alternative Character is NULL while writing to a file

Neelesh K J Jain27-Feb-09 6:06

Neelesh K J Jain

27-Feb-09 6:06

Thank you Stuart,
Can you please help in converting from ASCII to Unicode and vice versa, so that I don't face this problem in either of the conversion.

Neelesh K J Jain.

Re: Every Alternative Character is NULL while writing to a file

Iain Clarke, Warrior Programmer27-Feb-09 7:45

Iain Clarke, Warrior Programmer

27-Feb-09 7:45

This will answer more questions than you thought you had:
http://www.codeproject.com/KB/string/cppstringguide1.aspx[^]

Iain.

Codeproject MVP for C++, I can't believe it's for my lounge posts...

Re: Every Alternative Character is NULL while writing to a file

Stuart Dootson27-Feb-09 8:16

Stuart Dootson

27-Feb-09 8:16

If you're using VC++2003, 2005 or 2008, it's very easy. If you #include <atlconv.h>, you have various string conversion macros[^] available.

If you're using Visual C++ 6, you have similar macros[^] available.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

numbers per line

jonig1927-Feb-09 4:40

jonig19

27-Feb-09 4:40

I have a print method here. I'm trying to print lets say 3 numbers per line ( print(2);). If I had 7 elements, my output would be.

10 12 13
11 15
17 12

How do I get that first line to only print two? Is it going to be something with i % num?

public void print( int num )
{
   if( num < 1 )
      num = 1;
   for(int i = 0; i < size; i++)
   {
      System.out.print(list[i] + " ");
      if( i != 0 && i % num == 0)
         System.out.println();
   }
}

Re: numbers per line

Stuart Dootson27-Feb-09 5:40

Stuart Dootson

27-Feb-09 5:40

Hmmmm - that's not C++, is it - that's C#. Wrong forum, me bucko!

But anyway - the reason is because your test is wrong. Should be if(i % num == (num-1)).

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: numbers per line

jonig1927-Feb-09 8:36

jonig19

27-Feb-09 8:36

I tried that, but it will print something like

10 12
14 13 15

and that still isn't right.
I figured it out, it's actually my System.out.println(list[i]) has to come after the if statement.
Java too btw. Thanks for the idea though.

Re: numbers per line

Stuart Dootson27-Feb-09 8:51

Stuart Dootson

27-Feb-09 8:51

This worked OK when I translated it to C++:

public void print( int num )
{
   if( num < 1 )
      num = 1;
   for(int i = 0; i < size; i++)
   {
      System.out.print(list[i] + " ");
      if( i % num == (num-1) || i==size-1)
         System.out.println();
   }
}

in roughly comparable idiomatic C++, this is:

void print(std::vector<int> const& list, int num )
{
   if( num < 1 )
      num = 1;
   for(int i = 0; i < list.size(); i++)
   {     
      std::cout << list[i] << " ";      
      if( i % num == (num-1) || i==list.size()-1)
         std::cout << std::endl;      
   }
}

jonig19 wrote:
Java too btw

Java, C# - I wasn't a million miles away Smile | :)

Maybe I ought to add C# to my sig!

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.