LOADFILEOPTION

typedef struct _LOADFILEOPTION 
{ 
   L_UINT uStructSize; 
   L_INT XResolution; 
   L_INT YResolution; 
   L_UINT Flags; 
   L_INT Passes; 
   L_INT PageNumber; 
   L_UINT GlobalLoop; 
   L_IFDTYPE IFD; 
   L_UINT uRedScan; 
   L_UINT uGreenScan; 
   L_UINT uBlueScan; 
   L_UINT Flags2; 
   L_UINT64 IFD64; /* 32-bit apps only */ 
   L_VOID *pFilterData; 
   L_SIZE_T uFilterDataSize; 
   L_INT nFilter; 
   L_INT nAttachment; 
} LOADFILEOPTION, * pLOADFILEOPTION; 

The LOADFILEOPTION structure specifies extra options for reading an image file.

Members

uStructSize

Size of the LOADFILEOPTION structure. This should be sizeof(LOADFILEOPTION). You must fill this member.

XResolution

Horizontal dots per inch.

YResolution

Vertical dots per inch.

Flags

Any of the following flags. (Use a bitwise OR to specify more than one value.)

Passes

The number of passes (scans over the image) when loading or saving a progressive JPEG or LEAD CMP file. (This value is also used when loading interlaced PNG files.) (This value is also used when loading JBIG files to determine the number of resolutions to load to create a progressive load effect.)

Possible values when loading a progressive file:

PageNumber

The page number of a multipage file, which can contain more than one image. When loading a file, this is the exact page number. For more information on multipage files refer to Multi-page File Formats.

GlobalLoop

Loop count when playing an animation. Use 0 for continuous looping. For no looping, turn off the ELO_GLOBALLOOP flag in the Flags field.

IFD

Offset within a TIFF file where a page starts. This serves as a reference page for loading pages to a large TIFF file.

uRedScan

(NITF only) Index of the scan to be loaded for the red component. Used only if ELO_MULTISPECTRALSCAN is set.

uGreenScan

(NITF only) Index of the scan to be loaded for the green component. Used only if ELO_MULTISPECTRALSCAN is set.

uBlueScan

(NITF only) Index of the scan to be loaded for the blue component. Used only if ELO_MULTISPECTRALSCAN is set.

Flags2

Any of the following flags. (You can use a bitwise OR to specify more than one value.)

IFD64

Use to access pages with offsets > 4GB from very large BigTIFF files. It is not necessary to use IFD64 with regular TIFF files: just use the IFD offset. But of course, you can also access TIFF pages using this value.

In 64-bit applications, the IFD member is itself a 64-bit value. Therefore, the IFD can be used to access both TIFF and BigTIFF pages and the IFD64 member is not defined.            

IFD64 is defined for 32-bit builds only. This value is used only if Flags2 has the ELO2_USEIFD64 flag set.

According to specifications, the minimum value for the first IFD is 8 for TIFF files and 16 for BigTIFF files.

pFilterData

Pointer to a filter data structure used to speed up processing (loading, getting the file information, etc). Used only if Flags2 contains the ELO2_USEFILTERDATA flag. The filter data is retrived by passing the FILEINFO_USEFILTERDATA flag to L_FileInfo. If not NULL, free it using L_FreeFilterData when it is no longer needed.

See the Using Filter Data to Speed up Loading Large Files topic for more information.

uFilterDataSize

Size of the filter data. Used only if Flags2 contains the ELO2_USEFILTERDATA flag. The filter data is retrived by passing the FILEINFO_USEFILTERDATA flag to L_FileInfo.

If 0, it is possible that the filter data contains handles or pointers that are valid only in the current process. Also, if 0, the filter data can be used only in one thread at a time. Currently, this is the case for most filters.

If not 0, the filter data is flat and can be saved to disk and reloaded later.

See the Using Filter Data to Speed up Loading Large Files topic for more information.

nFilter

The filter that allocated the filter data. Used only if Flags2 contains the ELO2_USEFILTERDATA flag. The filter data is retrived by passing the FILEINFO_USEFILTERDATA flag to L_FileInfo.

See the Using Filter Data to Speed up Loading Large Files topic for more information.

nAttachment

1-based attachment number to load.

Comments

pLOADFILEOPTION is a pointer to an LOADFILEOPTION structure. Where the function parameter type is pLOADFILEOPTION, you can declare a LOADFILEOPTION variable, update the structure's fields, and pass the variable's address in the parameter. Declaring a pLOADFILEOPTION variable is necessary only if your program requires a pointer.

Load a stamp image by calling the L_ReadFileStamp function.

If ELO_SIGNED is set, the bitmap can contain negative pixel values. This can cause the image to be incorrectly painted when it is loaded. In order to load correctly, you must call L_ClearNegativePixels before loading the image. If ELO_SIGNED is not set, any negative pixels in the image will be cleared internally.

Notes:

• Loading JBIG files behaves as follows:

  1) If only one resolution exists in the JBIG File, then the FILEREADCALLBACK function will be called with the image data for that resolution as it is decompressed.

  2) If the image contains more than one resolution and (Passes >= nResolutions, where nResolutions represents the number of resolutions present in the file,) then FILEREADCALLBACK function will be called with the image data from the lowest resolution available in the file. The data that gets passed to the callback and/or inserted into the bitmap handle will be padded to the remaining width (that is, the size of the last resolution available in the file) with 0s. This will be repeated nResolution times, until the entire image (that is, the last resolution available) is loaded. Setting nPasses to CALLBACK_WHEN_MEANINGFUL or CALLBACK_ALWAYS has the same effect.

  3) If the image contains more than one resolution and (Passes is < nResolutions) then the process is the same as in case 2, except loading starts with the first resolution available, continues with the 2nd resolution, and so on, up to resolution Passes-1, and then loading is completed with the decompression of the last resolution available in the file.

• For more information about loading and saving large TIFF files faster, refer to Loading and Saving Large TIFF/BigTIFF Files.

ELO_MULTISPECTRALSCAN is used internally by the NITF filter. You do not need to use this flag.

When loading images for display purposes on platforms that expect image data to be in premultiplied alpha format, include the ELO_PREMULTIPLY_ALPHA flag for proper image display (i.e., the transparency information will be preserved). When loading images for image processing purposes do not include ELO_PREMULTIPLY_ALPHA, so image data will be loaded as it is actually stored in the input file (for proper pixel data manipulation).

The structure is used by:

• L_AnnLoad
• L_AnnLoadOffset
• L_AnnLoadMemory
• L_ReadLoadResolutions
• L_ReadFileTransforms
• L_FileConvert
• L_FileInfo
• L_FileInfoMemory
• L_GetLoadResolution
• L_GetFileCommentSize
• L_LoadBitmap
• L_LoadBitmapList
• L_LoadBitmapMemory
• L_LoadFile
• L_LoadFileTile
• L_LoadFileOffset
• L_LoadMemory
• L_ReadFileComment
• L_ReadFileCommentExt
• L_ReadFileCommentMemory
• L_ReadFileTag
• L_ReadFileTagMemory
• L_ReadFileStamp
• L_StartFeedLoad
• L_FileConvert
• L_LoadMemoryTile 

See L_GetDefaultLoadFileOption for information on default load options.