1.
The extension list associated with a specific filter.
LEADTOOLS will use the extension list specified by the value of pFilterInfo.pszExtensionList member to quickly test the file format. Whenever L_FileInfo function is called for a certain file, the file extension is matched against all the extension lists associated with the file filters. For example, the CMP filter is used to check for files with extensions cmp, jpg, jpeg or tif. If you have files with a certain extension intended to check, add them to the usual extension list and call L_SetFilterInfo function.
2.
The usage of extended filter checking for a file. This extended filter checking is specified by the value of pFilterInfo.uFlags member:
If the user sets this member to FILTERINFO_CHECKEDBYFILEINFO
flag, the extended filter checking will be used and the L_FileInfo
function will check a certain filter even if the extension does not match
the extension list.
If the user does not set this member
to FILTERINFO_CHECKEDBYFILEINFO flag, the extended filter checking will
not be used and the L_FileInfo function will check a certain filter ONLY
if the extension is in the extension list.
Some vectorial filters have a slow check to detect whether a file is of a certain format. In certain cases, the whole file needs to be parsed. If the run of L_FileInfo function is taking too long, the user can specify them not to be checked unless the file extension is one of the usual extensions associated with that filter.
The user can specify whether process of obtaining the file information of a filter will be slow or not by setting the value of the pFilterInfo.uFlags member to FILTERINFO_SLOWFILEINFO flag.
3.
The handling method of the filter either it will be ignored, fixed in the memory, or dynamically loaded. For more information, refer to L_IgnoreFilters and L_PreLoadFilters functions. The method of handling the filter is specified by the value of the pFilterInfo.uFlags member. If it is set to:
Handling Method:
Meaning:
FILTERINFO_IGNORED
The filter will be ignored. In this case, the user cannot load, save or get information for files handled by this filter. This flag overrides the other flags.
FILTERINFO_FIXED
The filter will be fixed in memory. Fixed filters will not be unloaded even when the maximum number of filters that can be loaded in memory is reached.
To set the maximum number of filters that will be loaded at a certain time, specify the value of nFixedFilters parameter of L_PreLoadFilters function.
FILTERINFO_DYNAMIC
The filter will be dynamically loaded and unloaded as required. LEADTOOLS will load filters when the user loads, save or check files of their corresponding format. When the maximum number of loaded filters has been reached, the least recently used filter will be unloaded.
To set the number of filters that can be loaded and unloaded dynamically, specify the value of nCachedFilters parameter of L_PreLoadFilters function.
This flag will be used automatically if the user did not set the pFilterInfo.uFlags member to either FILTERINFO_IGNORED or FILTERINFO_FIXED.
The user can check whether the filter is dynamic as the following:
(uFlags & FILTERINFO_LOADMASK) == FILTERINFO_DYNAMIC