No more that 23???

This is a discussion on No more that 23??? within the Windows Programming forums, part of the Platform Specific Boards category; Ok I ran into a problem and Im pulling my hair out trying to get around it. Im writing a ...

  1. #1
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    Jun 2008
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    No more that 23???

    Ok I ran into a problem and Im pulling my hair out trying to get around it. Im writing a small screen capture program that saves the bitmaps to disk, here is a simplified source of what im trying to do...

    Code:
    #include <windows.h>
    #include <stdio.h>
    
    //Copied from http://www.geocities.com/krishnapg/bitmap.html
    void SaveBitmap(char *szFilename,HBITMAP hBitmap)
    {
          HDC        hdc=NULL;
          FILE*      fp=NULL;
          LPVOID     pBuf=NULL;
          BITMAPINFO bmpInfo;
          BITMAPFILEHEADER  bmpFileHeader; 
          do{ 
                hdc=GetDC(NULL);
                ZeroMemory(&bmpInfo,sizeof(BITMAPINFO));
                bmpInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
                GetDIBits(hdc,hBitmap,0,0,NULL,&bmpInfo,DIB_RGB_COLORS); 
                if(bmpInfo.bmiHeader.biSizeImage<=0)
    				bmpInfo.bmiHeader.biSizeImage=bmpInfo.bmiHeader.biWidth*abs(bmpInfo.bmiHeader.biHeight)*
    				(bmpInfo.bmiHeader.biBitCount+7)/8;
    
                if((pBuf = malloc(bmpInfo.bmiHeader.biSizeImage))==NULL)
                {
                      MessageBox( NULL, "Unable to Allocate Bitmap Memory", "Error", MB_OK|MB_ICONERROR);
                      break;
                }            
                bmpInfo.bmiHeader.biCompression=BI_RGB;
                GetDIBits(hdc,hBitmap,0,bmpInfo.bmiHeader.biHeight,pBuf, &bmpInfo, DIB_RGB_COLORS);       
                if((fp = fopen(szFilename,"wb"))==NULL)
                {
                      MessageBox( NULL, "Unable to Create Bitmap File", "Error", MB_OK|MB_ICONERROR);
                      break;
                } 
    
                bmpFileHeader.bfReserved1=0;
                bmpFileHeader.bfReserved2=0;
                bmpFileHeader.bfSize=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+bmpInfo.bmiHeader.biSizeImage;
                bmpFileHeader.bfType='MB';
                bmpFileHeader.bfOffBits=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER); 
                fwrite(&bmpFileHeader,sizeof(BITMAPFILEHEADER),1,fp);
                fwrite(&bmpInfo.bmiHeader,sizeof(BITMAPINFOHEADER),1,fp);
                fwrite(pBuf,bmpInfo.bmiHeader.biSizeImage,1,fp); 
    
          }while(FALSE); 
                if(hdc)     ReleaseDC(NULL,hdc); 
                if(pBuf)    free(pBuf); 
                if(fp)      fclose(fp);
    }
    
    int WinMain(HINSTANCE h, HINSTANCE hp, LPSTR c, INT s){
    	int i;
    	for(i=1; i<=30; i++){
                    //Capture the screen
    		HDC dc = GetDC(NULL);
    		HDC cdc = CreateCompatibleDC(dc);
    		HBITMAP screen = CreateCompatibleBitmap(dc, 1280, 1024);
    		HBITMAP dummy = SelectObject(cdc, screen);
    		BitBlt(cdc, 0, 0, 1280, 1024, dc, 0, 0, SRCCOPY);
    		screen = SelectObject(cdc, dummy);
    
    		char TEMPFILE[255];
    		sprintf(TEMPFILE, "c:/bmp&#37;i.bmp", i);
    		
                    //Save the HBITMAP to disk
    		SaveBitmap(TEMPFILE, screen);
    	
    		DeleteObject(screen);
    		DeleteDC(cdc);
    		ReleaseDC(NULL, dc);
    	}
    	return 0;
    	
    }
    This code works fine and captures the full screen up to 23 times, after that it only creates 1kb bitmap files with a 0x0 resolution. Just to clarify, the first 23 runs through the 'for' loop work perfect but after that it just loses it and saves empty files and shows no error.

    If anyone can help me get more than 23 runs out of this I would be grateful

  2. #2
    Malum in se abachler's Avatar
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    Apr 2007
    Posts
    3,189
    Can you post the entire code?
    Until you can build a working general purpose reprogrammable computer out of basic components from radio shack, you are not fit to call yourself a programmer in my presence. This is cwhizard, signing off.

  3. #3
    Super Moderator VirtualAce's Avatar
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    9,596
    Or better yet attach the text version of it to your post. Placing it all in code blocks would result in a very long post and it is not needed.

  4. #4
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    Sorry if I didnt make myself clear - I rewrote what I was trying to do into this simple example to try and get it working so what you see above is the full source of that project at the moment. It compiles and runs ok in pellesC except for the problem mentioned in my last post...

  5. #5
    train spotter
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    Is the while loop the same in the actuall app?

    If the loop executes more than once you will lose the GDI objects and memory each loop as the clean up is only called once (after the while exits).
    "Man alone suffers so excruciatingly in the world that he was compelled to invent laughter."
    Friedrich Nietzsche

    "I spent a lot of my money on booze, birds and fast cars......the rest I squandered."
    George Best

    "If you are going through hell....keep going."
    Winston Churchill

  6. #6
    Algorithm Dissector iMalc's Avatar
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    The code that you appear to have copied form here http://www.geocities.com/krishnapg/bitmap.html is complete crap.
    Calling the function even once will result in leaking and using up all available memory or file handles and leave your app in an essentially useless state.
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

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