Please help with CString to float. - C / C++ / MFC Discussion Boards

normanS11-Oct-04 20:35

11-Oct-04 20:35

Interesting - I would not have thought of using a look-up table, but it should be slightly faster than shifting right by 4.

I assume that your look-up table looks something like this:

InValue OutValue<br />
  4095     255<br />
  4094     255<br />
  . . . . <br />
  4080     255<br />
  4079     254<br />
  . . . .<br />
   16       1<br />
   15       0<br />
  . . . .<br />
    0       0

Your approach should work, as you have described it. The only change I would suggest is that you don't need to treat each bit in the MS nibble individually.

I would do something like:

  // Get the MS byte and LS byte<br />
  LSByte = getNextByteFromFile();<br />
  MSByte = getNextByteFromFile();<br />
<br />
  // get the 12-bit intensity, with 1 arithmetic operation<br />
  totalValue = (int)LSByte + ((int)MSByte)<<8;<br />
  // This is the same as:<br />
  //  totalValue = (int)LSByte + ((int)MSByte)*256;<br />
  // and it is the same as your calculation, but should be faster<br />
  // because there is only one multiply / shift.<br />
<br />
  // then use LUT to get 8-bit value<br />
  newValue = LookUpTable[totalValue];<br />
<br />
  // then make an RGB-24 pixel<br />
  RGB24 = newValue + newValue<<8 + newValue<<16;

I think that this should give you a monochrome display which is really good. In my application I grab monochrome video frames from a camera at 8 bits per pixel, then I convert to RGB16, using a similar technique to above. This only leaves 5 bits per colour, and since R, G, B are the same, this means that I only end up with 32 different shades! The image which is displayed looks pretty good, although you can sometimes see the different grey levels. Your application will have 256 different shades of grey, which should give an excellent monochrome image!

DirectShow change resolution on the fly?

Indrawati10-Oct-04 14:13

Indrawati

10-Oct-04 14:13

Hi
I am programming a simple movie player with DirectShow now. Everything seems OK, the only thing I haven't been able to do is to change the movie resolution on the fly (for example, I want user to be able to specify, when the movie is running, whether they want to zoom in or zoom out, etc.) Could someone point me in the right direction on how to do this?

Thanks!

structure with vector as a member

gahziman10-Oct-04 13:30

gahziman

10-Oct-04 13:30

Hello:
I have this interesting problem...
I have to use a c-library that contains a function that is defined as follow:

int func(char * cpData);

I have been using a structure accually a nested structure as follows

struct A
{
char cString;
char cAnotherstring;
}sA;

struct B
{
int iIndex;
float fData[MAXDATA];

}sB;

struct C
{
struct A nA;
struct B nB[8];

}sStream;

I can call this structure with now problems
using func((char *) &sStream);

I wanted to use a vector for the float fData

such as the struct B is as follows:

struct B
{
int iIndex;
vector< float> fData;
} sB;

when I call the function I getting garbaged data.
I do take care of reserving the data size.
In fact I can see that the correct data is there just prior to calling
this legecy function.

Is there a way I can convert somehow to c-array which the function understand
but be able to use the advantage of the vector.

Your speedy reply wiill be vey much appreciated.

Re: structure with vector as a member

Mad__10-Oct-04 23:25

Mad__

10-Oct-04 23:25

Hy,

Change call to this:
func((char*)&sStream.nA)

Re: structure with vector as a member

gahziman11-Oct-04 0:34

gahziman

11-Oct-04 0:34

Sorry but the whole structure has to be sent.

Re: structure with vector as a member

Mad__11-Oct-04 0:39

Mad__

11-Oct-04 0:39

And how you wan't use C++ class vector in C library ? Smile | :)

Re: structure with vector as a member

Bob Stanneveld11-Oct-04 3:56

Bob Stanneveld

11-Oct-04 3:56

Hello,

The function takes a character array as an argument. Therefore, you cant pass a struct, unless you want to find out how the function accesses the memory...

A better way is to do your own data conversion prior to passing it to the function.

Multiply it by infinity and take it beyond eternity and you'll still have no idea about what I'm talking about.

Please help with CString to float.

Jochum Wittebrood10-Oct-04 10:29

Jochum Wittebrood

10-Oct-04 10:29

I'm sure its simple but I just can't seem to figure out how the get the number I have in a CString object into a float so I can do simple math on it.

I grab a CString from a CListBox, then use CString.MID to strip the string for some number values I want to add tax values to. Thats where I get stuck. Then the plan is to play with the float values and stick them into Static controls as CStrings again which I should be able to do with CString.Format.

I'm sure its just a silly beginer question, but I can't figure it out. Please help!

Jochum Wittebrood

Re: Please help with CString to float.

Jochum Wittebrood10-Oct-04 11:07

Jochum Wittebrood

10-Oct-04 11:07

I should also say i've tried: sscanf(CString,"%f",&float) which from what I have read on the web should be able to take CStrings but the compiler (MS Emmbedded visual C++ 3.0) tells me: cannot convert parameter 1 from 'class CString' to 'const char *'" so i've tried other ways to convert CString to LPTSTR and char[102] but i'm stuck. I can't think of what else to try. please help.

In VB all I used was something like: float = CCur (string)
I'm sure its not all the had in C++ but it seems to have me beat!

Thanks in Advance.
Jochum Wittebrood.

Re: Please help with CString to float.

Christian Graus10-Oct-04 11:54

Christian Graus

10-Oct-04 11:54

CString has a method to return the underlying char*, which you can then pass into atof. From memory, it's something like LockString, and you need to call a corresponding Unlock method when you've used the char * for whatever dastardly deed you intend. std::string has the c_str() function which does much the same thing. Sorry, it's too long since I lived in MFC land, I don't know the specific function you want. Hopefully this is enough to push you in the right direction Smile | :)

Christian

I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

Re: Please help with CString to float.

Jochum Wittebrood10-Oct-04 14:32

Jochum Wittebrood

10-Oct-04 14:32

I've had a look through the help docs for functions like that, but I can't find anything that I can get working. I can't find anything on LockString or c_str() maybe i'm not looking in the right places... It shouldn't be this hard should it?

Jochum

Re: Please help with CString to float.

Christian Graus10-Oct-04 14:41

Christian Graus

10-Oct-04 14:41

Jochum Wittebrood wrote:
It shouldn't be this hard should it?

WElcome to MFC....

The methods are GetBuffer and ReleaseBuffer.

Christian

I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

Re: Please help with CString to float.

Michael Dunn10-Oct-04 14:49

Michael Dunn

10-Oct-04 14:49

CString s = _T("123.456");
double d = _ttof(s);

--Mike--
Personal stuff:: Ericahist | Homepage
Shareware stuff:: 1ClickPicGrabber | RightClick-Encrypt
CP stuff:: CP SearchBar v2.0.2 | C++ Forum FAQ
----
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Re: Please help with CString to float.

toxcct10-Oct-04 21:00

toxcct

10-Oct-04 21:00

simple mathematic operations you say ?
look at this[^]

TOXCCT >>> GEII power

Re: Please help with CString to float.

callisthenes11-Oct-04 3:57

callisthenes

11-Oct-04 3:57

Use the generic C Runtime function _tstof().

See MSDN for more info...

Hope this helps...

Mike

Re: Please help with CString to float.

Jochum Wittebrood12-Oct-04 12:43

Jochum Wittebrood

12-Oct-04 12:43

Thanks for all your help guys, but I tried all the functions that you suggested and they all require 'const char' where the CString seems to be 'unsigned short'. The compiler always gives me convertion errors...

It must be my VB background but I can't seem to get my head around this, while people must use it in code all the time. Does anyone have a small snippit of code to show me how they do it?

This is what I've got...

int ListIndex;
CString WorkingStr;
CString TempStr;
float TAG;

CListBox * List1=(CListBox *)GetDlgItem(IDC_LIST1);

ListIndex = List1->GetCurSel();

List1->GetText(ListIndex,WorkingStr);

TempStr = WorkingStr.Mid(54,8);

TAG = atof(TempStr);

So we know that last line is the problem, but what can I do to fix it?

Thanks for your help.

Jochum

Runtime ComboBox Question

otrcomm10-Oct-04 9:04

otrcomm

10-Oct-04 9:04

Hello,

I know how to change the dropdown width of a combobox during runtime, but does anyone know how to change the width of the actual combobox at runtime?

Thanks,
Murrah Boswell

Re: Runtime ComboBox Question

Antti Keskinen10-Oct-04 9:23

Antti Keskinen

10-Oct-04 9:23

The combo box is the actual control, and the drop-down list box is a child of the combo box.
- To set the width of the list box, send a CB_SETDROPPEDWIDTH message (Win32) or call CComboBox::SetDroppedWidth (MFC).
- To set the width of the combo box control, call SetWindowPos (Win32) or CWnd::SetWindowPos (MFC).

Hope this helps you out.

-Antti Keskinen

----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.

Re: Runtime ComboBox Question

otrcomm10-Oct-04 12:03

otrcomm

10-Oct-04 12:03

Thanks for the replay,

How do I get the CWnd handle of my ComboBox?

Murrah Boswell

Re: Runtime ComboBox Question - Never Mind

otrcomm10-Oct-04 12:56

otrcomm

10-Oct-04 12:56

Disregard CWnd question, I figured it out!

Thanks for your help,
Murrah Boswell

Re: Runtime ComboBox Question

toxcct10-Oct-04 21:10

toxcct

10-Oct-04 21:10

GetDlgItem(MY_COMBO)

TOXCCT >>> GEII power

How l

lordmickel10-Oct-04 8:48

lordmickel

10-Oct-04 8:48

Hi, I've created a linked list and in my C++ source file I'm creating objects and passing them to a linked list in a loop. I want to loop over the linked list to show that the values are actually in the list. How would I do this?

I've uploaded all the code here if you want to take a look: http://www.hostmaster-x.co.uk/c++/

Thanks in advance for any help.

Cheers,

lordmickel Confused | :confused:

Re: How l

Christian Graus10-Oct-04 8:54

Christian Graus

10-Oct-04 8:54

If this is not homework, why are you not just using the list class included in C++ ?

Otherwise, just grab the first item, and keep stepping through the list, printing out each item as you go, or whatever else your homework requires. The code you've commented out looks like it should work, if your list is working.

Christian

I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

Re: How l

lordmickel10-Oct-04 9:21

lordmickel

10-Oct-04 9:21

Christian, thank you for your reply. This is homework - kind of. I'm not taking classes as such, just dabbling a little. From what you have said it would seem that the list isn't working correctly because when I uncomment the code I get the following output:

Please enter the driver's name then press enter:
driver1
name = driver1
driver2
name = driver2
driver3
name = driver3
name 1:

name 2:

name 1:

name 2:

Press any key to continue

Any ideas what the problem could be?

Cheers again,

lordmickel

Re: How l

Christian Graus10-Oct-04 9:30

Christian Graus

10-Oct-04 9:30

lordmickel wrote:
This is homework - kind of. I'm not taking classes as such, just dabbling a little.

Cool - I applaud that you're writing your own list then. Once it works, you'll understand how they work, and you should then use the STL exclusively Smile | :)

What happens when you step through the code in the debugger ? Are your values getting stored correctly in the list ? What about the pointer values as you step through, where do they go ?

Christian

I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer

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