Help with Printing BMPs

Hi there, Im trying to make a program that takes in a filename of a bmp and then prints out the BMP on a printer selected by the user. Below is the code I have written so far, and when I run it, it asks for the printer name then the filename name , and after i enter these the printer just feeds through 1 sheet of paper and doesnt print anything, I have no idea why, any help would be much appreciated, Thanx in advance.

Here comes the code :

Code:

#include <windows.h>
#include <windef.h>
#include <wingdi.h>
#include <stdio.h>
#include <winspool.h>
#include <fstream.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>

using namespace std;

class printer_select;

class imageprint{
        DOCINFO di;

        LPBITMAPINFO info;   // Struct for storing the DIB information,
                                         // it will be used by 'StretchDIBits()'
        HBITMAP      hbit;           // Handle to the bitmap to print
        BITMAP       bm;             // Struct used for obtaining information
                                       // about the bitmap (size, color depth...)
        int          nColors;   // store the number of colors the DIB has
        int          sizeinfo;   // Will contain the size of info
        RGBQUAD      rgb[256];       // Used to store the DIB color table
        int          YOUR_BITMAP_ID;

        public:
        imageprint(LPCTSTR file_name);
        imageprint(HANDLE fileinstance);
     //   int print(printer_select &printer_ptr);   do this later
        ~imageprint();

        };

 class printer_select {
      HDC pDC;
      TCHAR Device[50];

      public:
      
      printer_select();
      friend int imageprint::print(printer_select &printer_ptr);
      ~printer_select();
      
      };

 imageprint::imageprint(LPCTSTR file_name){

         nColors  = 0;   //store the number of colors the DIB has
         sizeinfo = 0;   // Will contain the size of info

                              // The following line loads the bitmap from a file
          hbit = (HBITMAP) LoadImage(0,
                                                         file_name,
                                                         IMAGE_BITMAP,
                                                         0,
                                                         0,
                                  LR_CREATEDIBSECTION | LR_LOADFROMFILE);

                        // Obtain information about 'hbit' and store it in 'bm'
  
  GetObject(hbit, sizeof(BITMAP), (LPVOID) &bm);

   int nColors = (1 << bm.bmBitsPixel);
   if(nColors > 256)
   nColors=0;  // This is when DIB is 24 bit.

                     
// Color table is only needed when the DIB has 256 colors or less.

 sizeinfo = sizeof(BITMAPINFO) + (nColors * sizeof(RGBQUAD));
 // This is the size required

 info = (LPBITMAPINFO) malloc(sizeinfo);     // Storing info in memory

 // Before 'StretchDIBits()' we have to fill some "info" fields.
 // This information was stored in 'bm'.

 info->bmiHeader.biSize          = sizeof(BITMAPINFOHEADER);
 info->bmiHeader.biWidth         = bm.bmWidth;
 info->bmiHeader.biHeight        = bm.bmHeight;
 info->bmiHeader.biPlanes        = 1;
 info->bmiHeader.biBitCount      = bm.bmBitsPixel * bm.bmPlanes;
 info->bmiHeader.biCompression   = BI_RGB;
info->bmiHeader.biSizeImage     = bm.bmWidthBytes*bm.bmHeight;
info->bmiHeader.biXPelsPerMeter = 0;
info->bmiHeader.biYPelsPerMeter = 0;
info->bmiHeader.biClrUsed       = 0;
info->bmiHeader.biClrImportant  = 0;

di.cbSize = sizeof(DOCINFO);
di.lpszDocName = file_name;
di.lpszOutput = (LPTSTR) NULL;

if(nColors <= 256)
{
  HBITMAP hOldBitmap;
  HDC     hMemDC     = CreateCompatibleDC(NULL);    

  hOldBitmap = (HBITMAP) SelectObject(hMemDC, hbit); 
  GetDIBColorTable(hMemDC, 0, nColors, rgb); 

  // pass this color information to "info"
  for(int iCnt = 0; iCnt < nColors; ++iCnt)
  {
    info->bmiColors[iCnt].rgbRed   = rgb[iCnt].rgbRed;
    info->bmiColors[iCnt].rgbGreen = rgb[iCnt].rgbGreen;
    info->bmiColors[iCnt].rgbBlue  = rgb[iCnt].rgbBlue;
  }

  SelectObject(hMemDC, hOldBitmap);
  DeleteDC(hMemDC);
}


}




imageprint::~imageprint(){
DeleteObject(hbit);

}




 int imageprint::print(printer_select &printer_ptr){
  
   //'StretchDIBiting'! 'pDC' is the printer DC
   HDC hdc = CreateCompatibleDC(printer_ptr.pDC); 

 StartDoc(printer_ptr.pDC, &di);
 StartPage(printer_ptr.pDC);

StretchDIBits(hdc,
              0,             //initial_pos_x
              0,              //initial_pos_y
              info->bmiHeader.biWidth, //size_x
              info->bmiHeader.biHeight, //size_y
              0,
              0,
              bm.bmWidth,
              bm.bmHeight,
              bm.bmBits,
              info,
              DIB_RGB_COLORS,
              SRCCOPY);

  EndPage(printer_ptr.pDC);
  EndDoc(printer_ptr.pDC);
  return 0;
 
 }

printer_select::printer_select(){
cout<<"enter printername: ";
cin >> Device;
pDC = CreateDC("WINSPOOL",Device,NULL,NULL);
}


printer_select::~printer_select(){
DeleteDC(pDC);
}

int main(void)

{

printer_select *printer_ptr;

printer_ptr = new printer_select;

TCHAR filename[50];
cout << "enter filename to print: ";
cin >> filename;

imageprint first_image(filename);

first_image.print(*printer_ptr);
}

Does the bitmap load from file?

>>HDC hdc = CreateCompatibleDC(printer_ptr.pDC);

Any HDC has a 1x1 mono BMP in it when created. So your SetDIBits will fail.

try.....
Select the hbit into hdc,
catch the returned original bmp,
copy hdc to printer_ptr.pDC with BitBlt() or StretchBlt(),
Select the original bmp back,
Delete the hdc.



I do this by BitBlt()'ing or StretchBlt()'ing the image to the printers HDC (rather than setting the printers HDC bits).

Keep the bitmap in the compatible DC you create and clean both the HDC and BMP up after you have printed them.

Thanks novacain.
I realised the error in my code. This line

Code:

StretchDIBits(hdc,

should be like this

Code:

StretchDIBits(printer_ptr.pDC,

I also rewrote the program using the methods you suggested and they also worked. Thanks.
Now im gonna go improve and trim some of the fat off my code. Eventually I want to expand the code to be able to print any image format like jpg, gif etc from file. Anyone got any suggestions for the best way to do this?

GDI+ supports most image types.

Thanks again novacain, Ive been reading up on this gdi+ and it makes things a whole lot easier, reckon I can do the same as above in about 10 lines of code. And I thought I'd have to decode the jpeg files manually. lol

Hi Again , I've recoded the program to use gdi+, but i get some weird behaviour when i print out the image. Im using the drawimage method of the graphics class to send it to the printer, but when it prints out it prints out an image thats zoomed in (about 300%) to 1 of the corners. Heres the code for the printing part:

Code:

image_ptr->GetBounds(&boundsRect, &unit);

Rect destRect(GetDeviceCaps(pDC,PHYSICALOFFSETX),
                       GetDeviceCaps(pDC,PHYSICALOFFSETY), 
                       (int)GetDeviceCaps(pDC,HORZRES),
                       (int)GetDeviceCaps(pDC,VERTRES));

graphics->DrawImage(image_ptr,
                     destRect,           // X:40 Y:38 Width:2400 Height:3319
                    (int)boundsRect.X, //0
                    (int)boundsRect.Y,  //0
                    image_ptr->GetWidth(),  //3681
                    image_ptr->GetHeight(),  //5140
                    UnitPixel,
                    NULL,NULL,NULL
                  );

AFAIK the drawImage function works like the stretchdibits function and should scale the image to fit the destRect. So I cant see why it is printing out a zoomed in image. BTW the numbers in comments are the vlues obtained during debugging for the image im trying to print and for the printer im trying to use.

Id be very grateful if anyone can point out where Im going wrong. Thanks.