Handles the thumbnails generated by calling the L_BrowseDir function.


#include "l_bitmap.h"

L_INT pEXT_CALLBACK YourFunction(pBitmap, pszFilename, pFileInfo, nStatusCode, nPercent, pUserData)



The pointer to the bitmap handle referencing the thumbnail generated by L_BrowseDir. You can copy this bitmap, save it to file, insert it into a LEADTOOLS ImageList Control, or otherwise process it as needed in your application.

L_TCHAR* pszFilename

Character string containing the filename from which this thumbnail was generated.


Pointer to a FILEINFO structure containing information about pszFilename.

L_INT nStatusCode

Status code. If an error occurred during thumbnail generation, this will be < SUCCESS. Possible values are:

Value Meaning
<SUCCESS An error occurred.
SUCCESS [1] Image was loaded.
BROWSE_LOADING [2] Indicates image is being loaded, see nPercent.
BROWSE_SKIPPED [3] Indicates image was skipped because it was larger than the specified range in L_BrowseDir.
BROWSE_PRELOAD [4] Indicates that LEADTOOLS has found a file and is about to determine the file format. It will then attempt to create a thumbnail for it. If the user wishes to avoid the internal file information processing, return ERROR_FILE_FORMAT. This will cause LEADTOOLS to skip the file.

L_INT nPercent

Represents the percentage completion of a file load when nStatusCode is equal to BROWSE_LOADING.

L_VOID* pUserData

A void pointer that you can use to access a variable or structure containing data that your callback function needs. This gives you a way to receive data indirectly from the function that uses this callback function. (This is the same pointer that you pass in the pUserData parameter of the calling function.). Keep in mind that this is a void pointer, which must be cast to the appropriate data type within your callback function.


Value Meaning
SUCCESS The function was successful.
< SUCCESS An error occurred. Return Codes


You must return SUCCESS to continue browsing for supported image files. The value you return from this callback will also be returned from L_BrowseDir.

Required DLLs and Libraries

See Also




For an example, refer to L_BrowseDir.

Help Version 22.0.2023.7.11
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LEADTOOLS Raster Imaging C API Help

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.