PRB: Image Corrupted When Using BLOAD to Load Into Video Memory

RESOLUTION

• Copy the files to a drive that does not use SMARTDrive or DoubleSpace (such as a RAM drive). Then use BLOAD to load the files from that drive.
• Use BLOAD to load the image into the memory occupied by a temporary dynamic array. Then move the image to video memory using PEEK and POKE. This method is slow but it works. For example:
  

  REDIM tmp(0 TO (BitPlaneSize - 1) \ 4) AS LONG  ' allocate memory
     DEF SEG = VARSEG(tmp(0))
     BLOAD f$, VARPTR(tmp(0))
     DIM j AS LONG
     FOR j = 0 TO BitPlaneSize - 1
        DEF SEG = VARSEG(tmp(0))
        DIM byte AS INTEGER
        byte = PEEK(VARPTR(tmp(0)) + j)
        DEF SEG = VideoPageSegment
        POKE j, byte
     NEXT
     REDIM tmp(0) AS LONG  ' deallocate memory
  						

• Use BLOAD to load the image into the memory occupied by a temporary dynamic array. Then move the image to video memory using the Microsoft C function _fmemcpy. This method is fast, but it requires the correct version of Microsoft C. For example:
  

     ' put the next statement at the module level, all on one line
     DECLARE SUB fmemcpy CDECL ALIAS "__fmemcpy" (BYVAL o%, BYVAL s%,
        SEG s AS ANY, BYVAL n%)
  ...
  
     REDIM tmp(0 TO (BitPlaneSize - 1) \ 4) AS LONG  ' allocate memory
     DEF SEG = VARSEG(tmp(0))
     BLOAD f$, VARPTR(tmp(0))
     CALL fmemcpy(0, VideoPageSegment, tmp(0), BitPlaneSize)
     REDIM tmp(0) AS LONG  ' deallocate memory
  						

• To use _fmemcpy in the interpreter environment, create a Quicklibrary named FMEMCPY.QLB by using the following commands:
  
  lib mlibce.lib *fmemcpy.obj;
  link /q fmemcpy.obj,,,vbdosqlb.lib mlibce.lib;
• To link an EXE that uses _fmemcpy, use the following command. Use VBDRT10E.LIB for the run-time module, or VBDCL10E.LIB for stand-alone:
  
  link <objects here>,,,vbdrt10e.lib mlibce.lib;