C / C++ / MFC

How to recognize table from PDF files by PageObject Rectangles?

28-Jun-12 13:03

I should re-word my question would would CInternetExcption catch an exception resulting from sockets

thnaks

Falconapollo27-Jun-12 19:41

Falconapollo

27-Jun-12 19:41

I want to recognize tables inside PDF, now I have rectangles of the PDF Text Objecthttp://i.stack.imgur.com/aHK3Q.png(the red rectangles in the picture).I'm confused about how to implement this rectangle algorithm. The programming language what I use is VC++.

What I want to get is:http://i.stack.imgur.com/aPxz1.png

The Result is a perfect table with header, rows, columns.Can anyone help me? How to rectangle table from these rectangles? These rectangles' orginal point (0, 0) is on the bottom-left point. x coordinate grow from left to right, and y coordinate grow from bottom to up.I don't want to use 3rd party. I want to implement this function through rectangle algorithm.

Any help would be greatly appreciated!

Re: How to recognize table from PDF files by PageObject Rectangles?

Richard MacCutchan27-Jun-12 22:22

Richard MacCutchan

27-Jun-12 22:22

PDF content is held in a codified format inside the file and the information about how to render it to a display device is kept with the data. You can either use one of the many free libraries available on the internet or, if you do not want to use a third-party library, you need to get a copy of the PDF specification from Adobe[^] and write your own handler.

speaking as ...

Exception handler newbie question

ForNow27-Jun-12 14:14

27-Jun-12 14:14

Hi,

I am basically a MFC newbie my background is MainFrame Assembler and I am begining to feel comfortable writting OO code

my next hurdle is execption processing I have read the documentation and MFC has its own abstract classes for exception handling

The way I am understanding it is as follows an exception is cought by a
catch paragraph.. depeding on the type e.g. for a memory exception I would have to have a derived class of CMemoryException e.g

class Mymemoryexception : public CMemoryException

and do catch (Mymemoryexception *)

If I want more information I would have to register a exception handler

my question is the following what is the scope of the exception handler

is it perthread meaning if the catch paragraph is executing whitin a thread then it

will catch all exceptions for the thread ??

is the scope per object ??

I guess I am hoping somebody can give a better expliantion then the documentation from
MSDN

thanks

Philippe Mori27-Jun-12 17:54

Philippe Mori

27-Jun-12 17:54

A catch clause will cath the specified exception and any derived exception.

In practice, if you don't write library for others, you rarely have to throw your own exception (and even less to catch them).

Generally you don't have to use exception handler and you should not have too much throw or catch in your code as exception are typically used for things that should not occurs.

MSDN documentation (and Google) are more complete documentation. It is not easy to explain it in a paragraph or two.

MFC and Visual C++ exception handling have some difference with standard C++ exceptions. For example catch ... will catch Win32 exceptions, MFC exceptions are thrown by pointer and exception specification is not implemented.

Philippe Mori

Sivaraman Dhamodharan28-Jun-12 1:39

Sivaraman Dhamodharan

28-Jun-12 1:39

Somebody will throw the ball and somebody should catch it. So you should know the possibility of piece of code that throws and should decide where to catch and what exactly to catch.

Say, if you place a try and catch block on the main() or Win main, and leave the catch block empty or look for a more generic CException, all the exception can be caught if it is not handled by the called functions. Which is bad in a big application with millions of code.

So define the try..catch to a narrow down piece of code, and catch the specific exception say filenotfound exception should caught from the piece of code that opens a file.

More Info: Exception Handling for C# Beginners[^]

Programming Article

ForNow28-Jun-12 2:43

28-Jun-12 2:43

would it work If I define multiple catchs each with a different exception type

thanks

David Crow28-Jun-12 3:48

David Crow

28-Jun-12 3:48

Sure.

try
{
    // do something
}
catch( CDBException dbException )
{
}
catch( CMemoryException memException )
{
}
catch( CResourceException resException )
{
}
catch(...)
{
}

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Show me a community that obeys the Ten Commandments and I'll show you a less crowded prison system." - Anonymous

ForNow28-Jun-12 7:25

28-Jun-12 7:25

Ok so howabout this to know what type of error I got in what object

class Myexception : public CException
{
public:
catchit();
}

Myexception::catchit()
{
catch( CDBException dbException )
{
ReportError(MB_OK,cdbexcpid..)
}
catch( CMemoryException memException )
{
}
catch( CResourceException resException )
{
}
catch(...)

ReportError(OK,typeofexcpid)
{

runtimeptr = GetRunTimeClass();

// report on type of error in what object

}

does this sound like doable idea

thanks

Peter_in_278028-Jun-12 3:52

Peter_in_2780

28-Jun-12 3:52

Adding to David's reply, if you have one exception derived (subclassed) from another one in the list, put the catch for the derived (more specific) exception first or you'll never get to it. For example, catch divide-by-zero before arithmetic-exception.

Cheers,
Peter

Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

help: image coordinates(x,y) in opencv with mfc

David Crow28-Jun-12 2:25

David Crow

28-Jun-12 2:25

ForNow wrote:
for a memory exception I would have to have a derived class of CMemoryException
e.g

class Mymemoryexception : public CMemoryException

Deriving your own class is not a requirement.

pthread_cancel issue

ytubis27-Jun-12 9:32

ytubis

27-Jun-12 9:32

Hi,
I have an issue when using this function,

the scenario is like that:
thread 1 invokes and creates thread 2 which monitors some data, using pthread_create with PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DEFERRED, then when thread 1 finishes his job it cancels thread 2 using pthread_cancel and everything is working fine, but the problem is that it seems that the threads are dead but still connected to the main projcess.
I am usin QNX OS which is a BSD flavor, same as Unix,

process view:

37560404 1 ./omadm_client 10r JOIN 5
37560404 2 ./omadm_client 10r CONDVAR
37560404 3 ./omadm_client 10r CONDVAR
37560404 4 ./omadm_client 10r REPLY
37560404 5 ./omadm_client 10r REPLY
37560404 6 ./omadm_client 10r DEAD
37560404 7 ./omadm_client 10r DEAD
37560404 8 ./omadm_client 10r DEAD
37560404 9 ./omadm_client 10r DEAD
37560404 10 ./omadm_client 10r DEAD

is it ok? how can I detach them from my main proccess? I do not see the point of uisn pthread_join unless it needs to be invoked for the termination process..

Many thanks,

Yossi,

Re: pthread_cancel issue

Luc Pattyn27-Jun-12 10:05

Luc Pattyn

27-Jun-12 10:05

It has been a long time since I used QNX, however what follows applies to all kernels and operating systems AFAIK:
- cancelling a thread often is unreliable; in general you don't know what state the thread and its data is in when you issue the cancel command, so you could end up with inconsistent data, with locked resources, etc.
- the better approach is "cooperative termination", where the thread's code helps in the thread either keeping active or exiting regularly.

So what I prefer to do in a monitoring thread typically looks like this (pseudo-code):

while(!enough) {
    do whatever is needed for monitoring
    wait a while
}

and when the caller wants it to terminate, just have it set the global boolean "enough" to true, the monitoring thread will exit (although not immediately, but that most often is OK).

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: pthread_cancel issue

ytubis27-Jun-12 10:31

ytubis

27-Jun-12 10:31

Hi,
Thanks for the answer,
it is a problem because this thread is monitoring a file which it waits (sleeps) on it till something changes, so if nothing changes we will still sleep on the IO forever,

I free the global resources of the thread so this is not my cuncern, but do you know how to detach the thread from the process?

Many thanks,

Yossi,

Re: pthread_cancel issue

Luc Pattyn27-Jun-12 11:06

Luc Pattyn

27-Jun-12 11:06

ytubis wrote:
do you know how to detach the thread from the process?

Sorry, I don't recall. I'm sure you could find that easily in the doc though.

ytubis wrote:
if nothing changes we will still sleep on the IO forever

I tend never to do that; when the OS supports it, I prefer giving a reasonable timeout to all system calls, and then implement my own loop around it (possibly with logging and other logistics).

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

jawadali47726-Jun-12 19:07

jawadali477

26-Jun-12 19:07

hi i have developed program using opencv with mfc and i can't get the coordinates (x,y) of image in the static box using mouse click. image opens in separate window. the code is as:

void on_mouse( int evt, int x, int y, int flags, void* param )
{
	if (evt = CV_EVENT_LBUTTONDBLCLK)
	{
	   CString Blue, Green;
		Blue.Format(_T("%d"), x);
		Green.Format(_T("%d"), y);
		SetDlgItemText(m_hWnd, IDC_Blue, Blue);
		SetDlgItemText(m_hWnd, IDC_Green, Green);
	}

}

the handle

HWND m_hWnd;

is defined at beginning where the header files are included (i might be doing it wrong since i'm not good at programming with handle). the mouse callback function is defined in a thread as

cvSetMouseCallback("box.png", on_mouse, 0);

any idea what is wrong with this code.

Regards
Jawad

Re: help: image coordinates(x,y) in opencv with mfc

SoMad26-Jun-12 20:00

Re: help: image coordinates(x,y) in opencv with mfc

26-Jun-12 20:00

You are not specifying exactly what the problem is, but I am going to guess that you look at the x and y values and determine that they are incorrect.
If that is the case, try calling ScreenToClient()[^] to convert the screen coordinates to client coordinates of your dialog. You have to pass in the m_hWnd of you dialog as the first parameter.

Soren Madsen

jawadali47726-Jun-12 20:12

jawadali477

26-Jun-12 20:12

sorry for not well explained
actually the problem is that static box does not show any value when mouse is being clicked. means it remains unchanged as it was.

Jawad

Re: help: image coordinates(x,y) in opencv with mfc

SoMad26-Jun-12 20:32

Re: help: image coordinates(x,y) in opencv with mfc

26-Jun-12 20:32

Oh, I see what you mean now.

You have a bug right there in your code. I am not sure if you get all mouse events in this handler (including mouse move events), but you should fix it and see if that solves your problem.

Change

C++

if (evt = CV_EVENT_LBUTTONDBLCLK)

C++

if (evt == CV_EVENT_LBUTTONDBLCLK)

Soren Madsen

David Crow27-Jun-12 2:38

David Crow

27-Jun-12 2:38

SoMad wrote:
...but you should fix it and see if that solves your problem.

True it should be fixed, but it won't make a difference as the expression (evt = CV_EVENT_LBUTTONDBLCLK) always evaluates to true.

Re: help: image coordinates(x,y) in opencv with mfc

SoMad27-Jun-12 4:33

Re: help: image coordinates(x,y) in opencv with mfc

27-Jun-12 4:33

Yes, I had originally written that in my message, but took it out. At the time I was thinking there might be more code in this function that he had not included - like this could have been an "else if" with an "if" above it having a similar error. Otherwise this code would be called all the time since the handler processes all mouse events including mouse move.

I think the problem has to do with the window handle and I don't really like this call from a separate thread.

Soren Madsen

SoMad26-Jun-12 21:23