## BUG: StretchDIBits() Prints Wrong Part of DIB with PSCRIPT.DRV

Q100354

The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1

## SYMPTOMS

When using StretchDIBits() to print a section of a device-independent bitmap (DIB) with the Windows version 3.1 PostScript printer driver, in some cases the wrong part of the DIB is printed. When printing the entire DIB, StretchDIBits() works correctly.

## STATUS

Microsoft has confirmed this to be a bug in version 3.5 of the PostScript printer driver (PSCRIPT.DRV) that shipped with Windows 3.1. The problem also occurs with version 3.55 of the PostScript driver that is currently available in the Windows Driver Library (WDL).

## MORE INFORMATION

Below is the function prototype for StretchDIBits():

    int StretchDIBits(hdc, XDest, YDest, cxDest, cyDest, XSrc, YSrc, cxSrc,
                      cySrc, lpvBits, lpbmi, fuColorUse, fdwRop)
    HDC hdc;                      // Handle of device context
    int XDest;                    // X-coordinate of destination rectangle
    int YDest;                    // Y-coordinate of destination rectangle
    int cxDest;                   // Width of destination rectangle
    int cyDest;                   // Height of destination rectangle
    int XSrc;                     // X-coordinate of source rectangle
    int YSrc;                     // Y-coordinate of source rectangle
    int cxSrc;                    // Width of source rectangle
    int cySrc;                    // Height of source rectangle
    const void FAR* lpvBits;      // Address of buffer with DIB bits
    LPBITMAPINFO lpbmi;           // Address of structure with bitmap data
    UINT fuColorUse;              // RGB or palette indices
    DWORD fdwRop;                 // Raster operation

To print the entire DIB, set both XSrc and YSrc to 0 (zero). This starting location of (0,0) corresponds to the bottom-left corner of the DIB. If you do not want to print the bottom portion of the DIB, change the starting location. Typically, you increase YSrc to the desired value and leave XSrc at 0 (as well as adjusting cySrc appropriately) so that the starting location is at the beginning of a scan line in the DIB. If the value of YSrc is such that the distance from the beginning of the DIB to (XSrc, YSrc) crosses a 64K segment boundary, the wrong part of the DIB will be printed.
To print the top section of the DIB, the printer driver must adjust lpvBits, the pointer to the DIB bits. Unfortunately, the segment portion of the huge pointer to the DIB bits is not incremented correctly; only the offset portion is incremented. Because the pointer to the DIB bits is not adjusted correctly, it points to the wrong section of the DIB bits and the wrong part of the DIB is printed.
Until the printer driver is fixed, application developers should themselves adjust the pointer to the DIB bits. The values of the biHeight and biSizeImage fields in the BITMAPINFOHEADER also must be adjusted accordingly. All the necessary code to calculate the new value for lpvBits can be obtained from the sample program DIBVIEW or WINCAP.
For example:

    // PaletteSize() and WIDTHBYTES can be found in either DIBVIEW or WINCAP

     LPBITMAPINFOHEADER lpDIBHdr;  // Pointer to BITMAPINFO struct
                                   // casted to LPBITMAPINFOHEADER
     LPSTR lpDIBBits;              // Pointer to DIB bits
     char _huge *lpTempDIBBits;    // IMPORTANT - must be a huge pointer
     DWORD  dwPalSize;             // Number of bytes in DIB color table
     DWORD  dwNumBytes;            // Number of bytes from beginning of DIB
                                   // bits to (0, YSrc)
     DWORD  dwSize;                // Number of bytes from beginning of DIB
                                   // to (0, YSrc)
     DWORD  dwSaveHeight;          // Save original DIB biHeight
     DWORD  dwSaveSizeImage;       // Save original DIB biSizeImage
    ...

     // Number of bytes in the DIB's color table.
     dwPalSize = PaletteSize((LPSTR)lpDIBHdr);

     // WIDTHBYTES calculates the number of bytes in one scan line.
     // dwNumBytes is the number of bytes from the beginning of the DIB
     // bits to the location (0, YSrc) in the DIB.
     dwNumBytes = YSrc * WIDTHBYTES(lpDIBHdr->biWidth * lpDIBHdr->biBitCount);

     // dwSize is the number of bytes from the beginning of the DIB to
     // the location (0, YSrc) in the DIB.
     dwSize = dwNumBytes + dwPalSize + (DWORD)sizeof(BITMAPINFOHEADER);

     if (dwSize >= 65536)
     {
        // Carefully adjust the pointer to the DIB bits.
        // Important Note: Due to problems with versions 6.0 and 7.0
        // of the Microsoft C Compiler, manipulating the pointer in one
        // statement may result in the segment portion of the huge pointer
        // being adjusted incorrectly or not at all.
        lpTempDIBBits = (char huge *)lpDIBBits;
        lpTempDIBBits = lpTempDIBBits + dwNumBytes;
        dwSaveHeight =  lpDIBHdr->biHeight;
        dwSaveSizeImage =  lpDIBHdr->biSizeImage;
        lpDIBHdr->biHeight -=YSrc;
        lpDIBHdr->biSizeImage= WIDTHBYTES(lpDIBHdr->biWidth *
                                          lpDIBHdr->biBitCount) *
                                          lpDIBHdr->biHeight;
        YSrc = 0;
     }

     if (!StretchDIBits (hDC,                           // DestDC
                         XDest,
                         YDest,
                         DestWidth,
                         DestHeight,
                         XSrc,
                         YSrc,
                         SrcWidth,
                         SrcHeight,
                         lpTempDIBBits,                 // DIB bits
                         (LPBITMAPINFO) lpDIBHdr,
                         DIB_RGB_COLORS,                // wUsage
                         SRCCOPY))                      // dwROP
        dwError |= ERR_PRN_STRETCHDIBITS;

     if (dwSize >= 65536)
     {
        lpDIBHdr->biHeight = dwSaveHeight;
        lpDIBHdr->biSizeImage = dwSaveSizeImage;
     }

For additional information on WINCAP, please see the following article in the Microsoft Knowledge Base:

> Q97193 SAMPLE: WINCAP Captures Screens Using DIB API

DIBVIEW can be found in the SAMPLES directory of version 3.1 of the Windows Software Development Kit (SDK) and Visual C++ for Windows.
This is not an issue with Windows 95.

Additional query words: no32bit 3.10 buglist3.10

Keywords : kb16bitonly
Issue type :
Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310

Last Reviewed: November 6, 1999 © 2001 Microsoft Corporation. All rights reserved. Terms of Use.