C / C++ / MFC

3-May-06 6:27

Hi.

I am trying to obtain the pixel colors from a webcam feed. Ideally I would be able to put the color in an array for further analysis (even though I am new to C++, I think I have an elementary grasp of array manipulation).

I am trying to use the DX Capture program I obtained from codeguru (http://www.codeguru.com/Cpp/G-M/dir...icle.php/c6973 - in the "Home >> Visual C++ / C++ >> Graphics & Multimedia >> DirectX >> DirectShow"
category and is called "Simultaneous Previewing & Video Capture using DirectShow."), using Visual Studio C++ .NET 2003. I cannot figure out how to modify the program to obtain the pixel colors. It does not have to be this program, by the way - any suggestions of better programs would be welcome.

I suspect that Convert24Image or ImageCapture might be of use.

The overall purpose is to identify lit lines on the target image, which is an instrument screen that displays a line (possibly two) whenever the instrument is used.

If I have not included enough details, or I am not being clear, please tell me so.

Any help would be very much appreciated (and please be aware that I have just begun learning the C++ language).

Lessthannovice.
"Everything is always ok in the the end. If it's not ok, then it isn't the end."

Justin Tay3-May-06 7:00

Justin Tay

3-May-06 7:00

You could use GetFrame() to get the pointer to the BYTE array of the image data you are looking for. He does some conversions to ensure that this BYTE array is the image data in RGB24.

This is just a guess, I didn't test this code.

BYTE *pData;
GetFrame(&pData);
RGBTRIPLE *pImage = static_cast<RGBTRIPLE*>(pData);
for(int y = 0; y < m_nHeight; y++)
{
  for(int x = 0; x < m_nWidth; x++)
  {
    // Your pixels
    (pImage+(y*m_nWidth)+x)->rgbtBlue;
    (pImage+(y*m_nWidth)+x)->rgbtGreen;
    (pImage+(y*m_nWidth)+x)->rgbtRed;
  }
}

Lessthannovice3-May-06 12:15

3-May-06 12:15

Thanks for the reply. It's nice to know someone is willing to help me.

I didn't know where to insert the code, so I put it at the end of Convert24image. Its giving me a

c:\ Projects\DX Capture\VMR_Capture.h(35): fatal error C1083: Cannot open include file: 'vmr9.h': No such file or directory

message. The code works, however (I get a feed on the screen). With the new code, does rgbtBlue give me the blue intensity, rgbtGreen the green intensity and so on? In other words, can I use them as normal variables now?

Thanks again for the reply.

Justin Tay3-May-06 13:17

Justin Tay

3-May-06 13:17

Create a new function and call it when you need the pixel values. If you need the pixel values for every frame though, this is not a good way to go about it, and you'd be better off with using a SampleGrabber filter.

The error message indicates that you don't have the DirectShow include files in any of your include directories. Have you installed the latest Platform SDK?

Lessthannovice4-May-06 23:00

4-May-06 23:00

I will be needing the pixel values for every frame, but I do not know how to use a SampleGrabber filter. I will try and look into it - any pointers/suggestions would, in the meantime, be very helpful.

I have installed the latest Platform SDK, but I will reinstall it once more to make sure this is not the problem. Thanks for the suggestion.

Lessthannovice5-May-06 11:35

converting char* to ASCII85 encoded char*

5-May-06 11:35

Help anyone? I can distil the problem to this: How do I get the pixel RGB color information from a webcam frame, and for all frames in a webcam feed(using any Cisual Studio C++ .NET 2003 program)?

goodoljosh19803-May-06 4:53

goodoljosh1980

3-May-06 4:53

Does anyone have a simple way of encoding a char* through the ASCII85 encoding and outputting another char*?

I hate to write my own if it's easy to do elsewhere.

Thanks

Re: converting char* to ASCII85 encoded char*

Maxwell Chen4-May-06 7:06

Maxwell Chen

4-May-06 7:06

Please refer to THIS for encoding[^] and THIS for decoding[^].

Maxwell Chen

OpenProcess Fails

Abin3-May-06 4:41

Abin

3-May-06 4:41

What would you do if ::OpenProcess(PROCESS_VM_READ, FALSE, dwProcessID) fails with error code 5 (Access is denied)? Where dwProcessID is a valid process ID. Is there any way to work around this problem?

Hamid_RT3-May-06 5:01

3-May-06 5:01

OpenProcess(PROCESS_VM_READ, FALSE, GetCurrentProcessId());

if you want know dwProccessId in the example MSDN you can find one program that you can see dwProccessId from another proccess

David Crow3-May-06 7:46

David Crow

3-May-06 7:46

I would use the OpenProcessToken()/LookupPrivilegeValue()/AdjustTokenPrivileges() trio to gain access.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"We will be known forever by the tracks we leave." - Native American Proverb

Abin3-May-06 16:21

Abin

3-May-06 16:21

Could you please explain a bit more?

Trapping events of html elements in IE

David Crow4-May-06 2:15

David Crow

4-May-06 2:15

OpenProcessToken()

LookupPrivilegeValue()

AdjustTokenPrivileges()

Google for examples.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"We will be known forever by the tracks we leave." - Native American Proverb

rana743-May-06 4:41

rana74

3-May-06 4:41

I am confused on the use of htmldocument and htmlelementevents in MSHTML IE.
Do the element events bubble upto the document level?i.e. does implementing the htmldocumentevent interface ensure that the events fired at all the individual elements will be trapped?
If so,is there some way to know that the event of which element got fired in the Invoke method?

Transparent Shadows

jk chan3-May-06 3:52

jk chan

3-May-06 3:52

Hi all

I am working on a Windows based application.

The application windows is a custiom shape window . (for that i used Layered windows & region ) its working fine.

In this program i would like to give shadow to application window. (like the shadows in Popup menus , such that it should blend neatly with the background pixels on other windows ).

looking for Valuable suggestions ..
Thanks & regards
Krishnan Smile | :)

If u can Dream... U can do it

-- modified at 9:52 Wednesday 3rd May, 2006

Re: Transparent Shadows

Hamid_RT3-May-06 5:24

RegSetValueEx crashing with Access Violation

3-May-06 5:24

krishnadevank
I think I see your answer in the codeproject but i'm sorry i dont know address
in this program you can see shadow for controls and I think for window

Re: Transparent Shadows

Michael Dunn3-May-06 7:21

Michael Dunn

3-May-06 7:21

Add the CS_DROPSHADOW style to your window class.

--Mike--
Visual C++ MVP Cool | :cool:

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Re: Transparent Shadows

jk chan3-May-06 19:54

jk chan

3-May-06 19:54

hi Mike

Adding CS_DROPSHADOW is good idea .. But i want to chage the color of shadow
i want to give color shadows . Thats my problem.

Like this
The First color will be Color::Red
The Second wll be Color::Transparent

and i would like to paint it with a LinerGradientBrush.

What you think , Mike ?

If u can Dream... U can do it

-- modified at 1:54 Thursday 4th May, 2006

Rajni Kant3-May-06 3:46

Rajni Kant

3-May-06 3:46

I am trying to write a registry value (using RegSetValueEx) of 2182 bytes for a particlular value name of RG_SZ type. But VC++ 6.0 is allowing me to write value of only 2007 bytes. If the size is greater than 2007 bytes then my application crashes with Access Violation.

HKEY hCLSID = HKEY_CURRENT_USER;
KEY phk;
LPCTSTR SKey = "SOFTWARE\\Rajni";
DWORD lpdw=NULL
if(RegCreateKeyEx(hCLSID,SKey,0,NULL,REG_OPTION_NON_VOLATILE,KEY_ALL_ACCESS ,NULL,&phk,&lpdw) == ERROR_SUCCESS)
cout<<"Key created\n";
else
cout<<"Key Creation Failed\n";

TCHAR data[8192];
const char * lpValueN = "name";
DWORD dwBufLen = 8192;

if(RegSetValueEx(phk,lpValueN,0,REG_SZ,(unsigned char *)strValue,dwBufLen) == ERROR_SUCCESS)
cout<<"\nSet Value Successful\n";
else
cout<<"\nSet Value Failed\n";

here strvalue is of 2182 character long..

Plz help !!!!!!!!!!

thanks and regsrds,
Rajni Kant

James R. Twine3-May-06 3:52

James R. Twine

3-May-06 3:52

   I would start with correcting the call to RegSetValueEx(...) - the last parameter is the (byte) size of the data to be saved, not the size of the buffer used to store that data. When writing NUL-terminated strings, make sure the data length specified includes that terminating NUL.

   See if that helps.

   Peace!

-=- James

If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
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Hamid_RT3-May-06 4:13

3-May-06 4:13

I tested with length data but I think it's not problem
and I use LPTSTR for strValue but it doesnt work

James R. Twine3-May-06 4:31

James R. Twine

3-May-06 4:31

I believe the problem is with either the data or the specified length of it. The following example works correctly writing 8K or raw data and as a NUL-terminiated string (8K + 1 in that case):

BYTE    btaData[ 8192 + 1 ];
HKEY    hKey = NULL;

::srand( time( NULL ) );
for( DWORD dwChar = 0; dwChar < 8192; dwChar++ )
{
    do
    {
        btaData[ dwChar ] = ( ( rand() % 57 ) + 65 );
    }
    while( !::isalpha( btaData[ dwChar ] ) );
}
btaData[ 8192 ] = '0';

::RegCreateKeyExA( HKEY_CURRENT_USER, "Test", 0, 
        NULL, REG_OPTION_NON_VOLATILE, 
        ( STANDARD_RIGHTS_REQUIRED | KEY_SET_VALUE | 
        KEY_CREATE_SUB_KEY ), NULL, &hKey, NULL );
if( hKey )
{
    ::RegSetValueExA( hKey, "TestValByte", 0, REG_BINARY, btaData, 8192 );
    ::RegSetValueExA( hKey, "TestValSZ", 0, REG_SZ, btaData, 8193 );
    ::RegCloseKey( hKey );
}

-=- James

Hamid_RT3-May-06 4:55

3-May-06 4:55

I think I find answer can you test this code please.

Hamid_RT3-May-06 4:53