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

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) version 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 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;
 }

   ARTICLE-ID: Q97193
   TITLE     : SAMPLE: WINCAP Captures Screens Using DIB API

This is not an issue with Windows 95.