wiasWritePageBufToFile function (wiamdef.h)
The wiasWritePageBufToFile function writes the contents of a temporary page buffer to an image file.
Syntax
HRESULT wiasWritePageBufToFile(
[in] PMINIDRV_TRANSFER_CONTEXT pmdtc
);
Parameters
[in] pmdtc
Pointer to a MINIDRV_TRANSFER_CONTEXT structure.
Return value
On success, the function returns S_OK. If the function fails, it returns a standard COM error or one of the WIA_ERROR_XXX errors (described in the Microsoft Windows SDK documentation).
Remarks
The function writes data from a minidriver-allocated temporary page buffer to the image file opened by the WIA service. Minidrivers typically call this function after acquiring a page of data for which the minidriver allocated a temporary buffer.
This function is similar to wiasWriteBufToFile, which can be used to write a buffer of image data to any type of image file. If a WIA minidriver intends to write a page of image data to a multipage TIFF file, including all appropriate tags, image file directory (IFD) entries, and other nonimage data, it should call this function, rather than wiasWriteBufToFile.
The expression pmdtc->hFile contains the handle to the file in TYMED_FILE (and TYMED_MULTIPAGE_FILE) transfers. This can be used to directly access the file that is being written to.
An example of how to use it is:
SetFilePointer((HANDLE)(LONG_PTR)pmdtc->hFile,0,NULL,FILE_BEGIN);
if (!WriteFile((HANDLE)(LONG_PTR)pmdtc->hFile,
pMyBuffer,
dwNumBytesToWrite,
&dwNumBytesWritten,
NULL)) {
//
// Some error happened
//
.
.
.
}
However, if you are considering using just the file handle in your TYMED_FILE and TYMED_MULTIPAGE_FILE transfers (to write data directly to the file using the file handle, instead of calling wiasWritePageBufToFile), use wiasWriteBufToFile. This function performs the equivalent of:
bRet = WriteFile((HANDLE)ULongToPtr(pmdtc->hFile),
pmdtc->pTransferBuffer,
pmdtc->lItemSize,
&ulWritten,
NULL);
This is essentially what you would do if you used the file handle directly. The advantage of the first example is that if the implementation was changed in a future release of WIA (for example, if the WIA service began using pipes instead of files, internally), the driver would not need to be updated.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Available in Microsoft Windows Me and in Windows XP and later versions of the Windows operating systems. |
| Target Platform | Desktop |
| Header | wiamdef.h (include Wiamdef.h) |
| Library | Wiaservc.lib |
| DLL | Wiaservc.dll |