[bubba_169]

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...

#include <windows.h>
#include <stdio.h>

//Copied from www(dot)geocities(dot)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%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