C / C++ / MFC Discussion Boards

alex__b7-Apr-06 21:20

7-Apr-06 21:20

Thank you for answering, but no.
It was either MFC or WIN32 (before C#, .net etc)

What I do remember, the demo drew a polyline (orthogonal segments only) and allowed the user to move those points while keeping the orthogonality.

alex

'Architecture is music frozen in space.'

PGM image format - buffer vs file

georgie.moss7-Apr-06 2:38

georgie.moss

7-Apr-06 2:38

Hi - I don't usually like to post questions which are "here's some code - why doesn't it work?" but I am well and truly stumped on this one...it's been more than a whole day's effort so far and it is 1025 on friday night and i'm still working on it....so i'd really appreciate some help...

I have two functions, one takes a buffer, turns it into PGM format (P6) and saves it to file....the other takes the buffer, turns it into PGM format in place and the calling function then returns the buffer and it is displayed

the saving to file one works a treat
<code>
/*
* writes a colour PGM file from a buffer
*/</code>

<code>
int write_P6(char *name, int W, int H, unsigned char *buf)
{
FILE *f;
int i, j;

if( (f = fopen(name, "w")) == NULL)
{
printf("Could not open >%s<\n", name);
return FALSE;
}

fprintf(f,"P6\n %d %d\n 255\n",W, H);
fflush(f);

for(i=0;i<H;i++)
{
for(j=0;j<W;j++)
{
fwrite(buf + (i * W + j)*3+2, 1, 1, f);
fwrite(buf + (i * W + j)*3+1, 1, 1, f);
fwrite(buf + (i * W + j)*3 , 1, 1, f);
}
}
fclose(f);

return TRUE;
}
</code>

and I am able to display the images just fine, but obviously this is sub-optimal and the disk accesses makes it real slow

so i want to use this function instead
<code>
/*********************************************************************/
/*
* changes a rgb buffer in place into PGM format without saving to disk
*/

int make_P6(int W, int H, unsigned char *buf)
{
int i, j;
unsigned char* temp;
temp = (unsigned char*)malloc(x * y *3+15);

sprintf(temp, "P6\n %d %d\n 255\n",W, H);
for(i=0;i<H;i++)
{
for(j=0;j<W;j++)
{
sprintf(temp, buf + (i * W + j)*3+2);
sprintf(temp, buf + (i * W + j)*3+1);
sprintf(temp, buf + (i * W + j)*3);
}
}
buf = (unsigned char*)realloc(buf, x * y *3+15);
buf = temp;
free(temp);
return TRUE;
}
</code>
the calling getframe function looks kinda like this:
<code>
unsigned char * getframe(int save_file)
{
int ret ;

ret = read(fd1, s, x * y);
if( ret != (x * y ) )
{
printf("We will have fragmented picture\n" );
}
nb_frame ++ ;
bayer2rgb24(d, s, x, y);

// at this point we should have a raw, RGB image
if( save_file )
{
write_P6("P6.pgm", x, y, d);
}
else
{
d = make_P6(x,y,d);
}

return d;
}
</code>
and the function which calls getframe knows whether to disregard the return value and open the file, or look at the return value for the pic....

now the problem comes in make_P6 --> the code just hangs at

<code> sprintf(temp, buf + (i * W + j)*3+2);
sprintf(temp, buf + (i * W + j)*3+1);
sprintf(temp, buf + (i * W + j)*3);</code>

- if i comment out these lines, there is no freeze (but clearly, nothing sensible happens to the image)....but if i leave them there, it just kinda waits....doing nothing....not crashing.....not taking up heaps of resources

it doesn't make any sense to me because the line
<code>sprintf(temp, "P6\n %d %d\n 255\n",W, H);</code>
works just fine....

i'll be eternally grateful if somebody can give me a hand
XX georgia Blush | :O

-- modified at 8:40 Friday 7th April, 2006

Re: PGM image format - buffer vs file

David Crow7-Apr-06 2:51

David Crow

7-Apr-06 2:51

georgie.moss wrote:
sprintf(temp, buf + (i * W + j)*3+2);
sprintf(temp, buf + (i * W + j)*3+1);
sprintf(temp, buf + (i * W + j)*3);

Of these three statements, only the last one is of any use since they are all writing to the same address. Is this your intent?

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

"There is no death, only a change of worlds." - Native American Proverb

Re: PGM image format - buffer vs file

James R. Twine7-Apr-06 3:18

James R. Twine

7-Apr-06 3:18

sprintf expects to be working with NUL-terminated strings. If the buffer pointed to by buf + (i * W + j)*3+2 is garbage or does not have a NUL, it will keep looking for one. If that buffer contains a % it will try to format a value based on the contents of the stack, which would be bad considering to additional parameters are passed.

Are you sure you are not trying to do something like:

temp = (unsigned char*)malloc(x * y *3+15);
  
DWORD dwIndex = 0;
  
sprintf(temp, "P6\n %d %d\n 255\n",W, H);
for(i=0;i<H;i++)
{
   for(j=0;j<W;j++)
   {         
     DWORD dwBufIndex = ( i * W + j ) * 3 + 2;
  
     temp[ dwIndex++ ] = buf[ dwBufIndex ];   <code>// 3+2</code>
     temp[ dwIndex++ ] = buf[ --dwBufIndex ]; <code>// 3+1</code>
     temp[ dwIndex++ ] = buf[ --dwBufIndex ]; <code>// 3+0</code>
   }
}

My math/indices may be off but I am sure you get what I am talking about...

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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Re: PGM image format - buffer vs file

georgie.moss10-Apr-06 14:45

georgie.moss

10-Apr-06 14:45

thanks - changing from sprintf to direct buffer manipulation did the trick
really appreciate the help Big Grin | :-D

Status Bar Problem

si_697-Apr-06 1:56

si_69

7-Apr-06 1:56

Hi
I am trying to add a couple of items to the status bar in my SDI app, i can add one item on no problem, but when i add a second one on,
i get a message box appear saying "failed to create empty document"

in MainFrm i have

static UINT indicators[] =
{
ID_INDICATOR_CAPS,
ID_INDICATOR_NUM,
ID_INDICATOR_SCRL,
ID_INDICATOR_COUNT,

};

in the OnCreate
if (!m_wndStatusBar.Create(this) ||
!m_wndStatusBar.SetIndicators(indicators,
sizeof(indicators)/sizeof(UINT)))
{
TRACE0("Failed to create status bar\n");
return -1; // fail to create
}

m_wndStatusBar.SetPaneInfo(3,ID_INDICATOR_COUNT, SBPS_STRETCH, NULL );

in my resource.h

#define ID_INDICATOR_COUNT 59142

but if i try to add another option on i get the error

any ideas ??

Si

Re: Status Bar Problem

James R. Twine7-Apr-06 2:02

James R. Twine

7-Apr-06 2:02

   IIRC, status bar indicators need to be string table entries, so try adding a string table entry for ID_INDICATOR_COUNT. Note that string table entries cannot be blank, and you will want to use enough characters for the width that the indicator will need.

   For example, if you need to show a value range of 0-999999, I would create the string table entry with a string of "000000". You can set the value of the indicator using an ON_COMMAND_UPDATE_UI for the ID_INDICATOR_COUNT "control".

   Peace!

-=- James

A CString question

<color>Aljechin 7-Apr-06 1:29

<color>Aljechin

7-Apr-06 1:29

How much of characters could I store in a CString? I am having a function in which a CString has to be accepted. The input may be extremely large (Say about 700 pages, with 300 characters each page). Will CString be able to manage this? I know that I can chop the input to pieces and go ahead with the work. But I want to know how effective will be CString able to do this job. Thanks for your time..

Aljechin Alexander

Rose | [Rose]