L_CreateThumbnailFromFile
#include "l_bitmap.h"
L_LTFIL_API L_INT L_CreateThumbnailFromFile(pszFile, pBitmap, uStructSize, pThumbOptions, pfnCallback, pUserData, pLoadOptions, pFileInfo)
L_TCHAR* pszFile; |
/* name of the image file to load */ |
pBITMAPHANDLE pBitmap; |
/* pointer to the target bitmap handle */ |
L_UINT uStructSize; |
/* size in bytes, of the structure pointed to by pBitmap */ |
pTHUMBOPTIONS pThumbOptions; |
/* pointer to a structure */ |
FILEREADCALLBACK pfnCallback; |
/* optional callback function */ |
L_VOID* pUserData; |
/* pointer to more parameters for the callback */ |
pLOADFILEOPTION pLoadOptions |
/* pointer to optional extended load options */ |
pFILEINFO pFileInfo; |
/* pointer to a structure */ |
Creates a thumbnail from the specified image file.
Parameter |
Description |
pszFile |
Character string containing the name of the file to load. |
pBitmap |
Pointer to the bitmap handle for the loaded data. |
uStructSize |
Size in bytes, of the structure pointed to by pBitmap, for versioning. Use sizeof(BITMAPHANDLE). |
pThumbOptions |
Pointer to a structure containing thumbnail generation options. Pass NULL to get the default options. |
pfnCallback |
Optional callback function for additional processing. |
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If you do not provide a callback function, use NULL as the value of this parameter. |
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If you do provide a callback function, use the function pointer as the value of this parameter. |
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The callback function must adhere to the function prototype described in FILEREADCALLBACK Function. |
pUserData |
Void pointer that you can use to pass one or more additional parameters that the callback function needs. |
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To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure. |
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If the additional parameters are not needed, you can pass NULL in this parameter. |
pLoadOptions |
Pointer to optional extended load options. Pass NULL to use the default load options. |
pFileInfo |
Pointer to a FILEINFO structure. This structure may contain file information used in loading an image, or it may be updated with information about the file being loaded. |
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If nothing is known about the file, pass NULL for this parameter, or declare a variable of type FILEINFO and set the FILEINFO. Flags to 0, then pass the address of the FILEINFO structure in this parameter. In this case, if the address of a FILEINFO structure is passed, the FILEINFO structure will be updated with the results of L_FileInfo. |
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If only the file type is known, set pFileInfo.Format to the file type and set pFileInfo.Flags to FILEINFO_FORMATVALID. This can also be done if L_FileInfo has been called previously, but values that affect the size of the image loaded have been changed (for example, by calling L_SetPCDResolution or L_SetWMFResolution). In this case the FILEINFO structure pointed to by pFileInfo will be updated with the results of L_FileInfo. |
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If L_FileInfo has been called prior to calling this function, and no changes have been made to the contents of the structure filled by L_FileInfo, then the address of the filled FILEINFO structure can be passed for this parameter. In this case, the FILEINFO.Flags member should be set to FILEINFO_INFOVALID. The L_FileInfo function will set the FILEINFO.Flags to FILEINFO_INFOVALID. In this case the load will be faster since this function does not have to query the file filters for the file type. |
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Note: Local variables are not initialized (since they are placed on the stack). So if you have a FILEINFO structure as a local variable, the value of its Flags parameter is undefined, possibly having FILEINFO_INFOVALID or FILEINFO_FORMATVALID set. That is why it is important to initialize FILEINFO.Flags before passing the address of the FILEINFO structure to the function. |
Returns
SUCCESS |
The function was successful. |
< 1 |
An error occurred. Refer to Return Codes. |
Comments
This function is used internally by L_BrowseDir to create/load the thumbnails for each file that is enumerated. You can use this function to manually create the thumbnail for a specified image file.
Since the function allocates storage to hold the image, it is up to you to free this storage by calling L_FreeBitmap.
The default thumbnail options are:
DefThumbOpt.nWidth |
= 80; |
DefThumbOpt.nHeight |
= 80; |
DefThumbOpt.nBits |
= 0; |
DefThumbOpt.uCRFlags |
= 0; |
DefThumbOpt.bMaintainAspect |
= TRUE; |
DefThumbOpt.bForceSize |
= FALSE; |
DefThumbOpt.crBackColor |
= RGB(0,0,0); |
DefThumbOpt.bLoadStamp |
= TRUE; |
DefThumbOpt.bResample |
= FALSE; |
Note: More options are available in the LOADFILEOPTION structure.
Required DLLs and Libraries
LTFIL For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application. |
Platforms
Windows 2000 / XP/Vista, Windows CE.
See Also
Functions: |
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Topics: |
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Example
L_INT CreateThumbnailFromFileExample(L_VOID) { BITMAPHANDLE LeadBitmap; L_INT nRet; THUMBOPTIONS opt; L_TCHAR * szFilename= TEXT("C:\\Program Files\\LEAD Technologies\\LEADTOOLS 15\\Images\\IMAGE1.CMP"); //Create a thumbnail with default options, and no callback nRet = L_CreateThumbnailFromFile(szFilename, &LeadBitmap, sizeof(BITMAPHANDLE), NULL, NULL, NULL, NULL, NULL); if(nRet == SUCCESS) { if(LeadBitmap.Flags.Allocated) L_FreeBitmap(&LeadBitmap); } //Create a thumbnail with some options, and no callback memset(&opt, 0, sizeof(THUMBOPTIONS)); opt.uStructSize = sizeof(THUMBOPTIONS); opt.bLoadStamp = FALSE; opt.nHeight = 40; opt.nWidth = 80; opt.bForceSize = TRUE; opt.bMaintainAspect = TRUE; opt.crBackColor = RGB(255,0,0); nRet = L_CreateThumbnailFromFile(szFilename, &LeadBitmap, sizeof(BITMAPHANDLE), &opt, NULL, NULL, NULL, NULL); if(nRet == SUCCESS) { if(LeadBitmap.Flags.Allocated) L_FreeBitmap(&LeadBitmap); } return SUCCESS; }