L_LoadFileOffset

#include "l_bitmap.h"

L_LTFIL_API L_INT L_LoadFileOffset(fd, nOffsetBegin, nBytesToLoad, pBitmap, uStructSize, nBitsPerPixel, nOrder, uFlags, pfnCallback, pUserData, pLoadOptions, pFileInfo)

Loads an image from a file, using a callback function, and letting you specify the location of the image data within the file. This enables you to load an image file that is embedded in another file.

Parameters

L_HFILE fd

The Windows file handle of the file to load.

L_OFFSET nOffsetBegin

The position, from the beginning of the file, of the first byte to load.

L_OFFSET nBytesToLoad

The size of the embedded image file. (The embedded file may be a record within the larger file, and in such cases, this is the record size.)

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle for the loaded data.

L_UINT uStructSize

Size in bytes, of the structure pointed to by pBitmap, for versioning. Use sizeof(BITMAPHANDLE).

L_INT nBitsPerPixel

Resulting bitmap pixel depth. The following are valid values:

Value	Meaning
0	Keep the original file's pixel depth. (Do not convert). A Special Note about Loading 12- and 16-bit Grayscale Images.
1 to 8	The specified bits per pixel in the resultant bitmap
12	12 bits per pixel in the resultant bitmap
16	16 bits per pixel in the resultant bitmap
24	24 bits per pixel in the resultant bitmap
32	32 bits per pixel in the resultant bitmap
48	48 bits per pixel in the resultant bitmap
64	64 bits per pixel in the resultant bitmap

L_INT nOrder

The desired color order. Possible values are:

Value	Meaning
ORDER_RGB	[0] Red-green-blue order.
ORDER_BGR	[1] Blue-green-red order.
ORDER_GRAY	[2] 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are only supported in Document and Medical Imaging toolkits.
ORDER_RGBORGRAY	[3] Load the image as red, green, blue OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in Document and Medical Imaging toolkits.
ORDER_BGRORGRAY	[4] Load the image as blue, green, red OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in Document and Medical Imaging toolkits.
0	The data is 8 bits per pixel or less.
ORDER_ROMM	[5] ROMM order. ROMM only supports 24 and 48-bit images.
ORDER_BGRORGRAYORROMM	[6] Load the image as red, green, blue OR as a 12 or 16-bit grayscale image OR as ROMM. 12 and 16-bit grayscale images are supported in Document and Medical Imaging toolkits. ROMM only supports 24 and 48-bit color images.

L_UINT uFlags

Binary flags that determine the behavior of L_LoadFileOffset. You can specify one or more of the following values:

Value	Meaning
LOADFILE_ALLOCATE	[0x0001] The function allocates memory for the specified bitmap.
LOADFILE_STORE	[0x0002] The function loads data into the specified bitmap. (This takes place in addition to the actions of your callback function.)
LOADFILE_FIXEDPALETTE	[0x0004] This flag will force a palletized image to be dithered to a fixed palette.
LOADFILE_NOINTERLACE	[0x0008] The function passes image data in the order that is displayed, regardless of how it is stored in the file. (Set this flag if your program does not handle interlaced file formats.)
LOADFILE_ALLPAGES	[0x0010] The function loads all pages of a multipage file. Use this flag only if you are creating a bitmap list using the L_AppendPlayback function.
LOADFILE_COMPRESSED	[0x0040] (Document and Medical Imaging toolkits) If possible, load the file as a 1-bit RLE-compressed image. For more information, refer to Speeding Up 1-Bit Documents.
LOADFILE_SUPERCOMPRESSED	[0x0080] (Document and Medical Imaging toolkits) Load 1-bit or 24-bit images as super compressed. This flag is ignored if the bitmaps are not loaded as 1-bit or 24-bit.
LOADFILE_MULTITHREADED	[0x2000] Use Multithreaded load

FILEREADCALLBACK pfnCallback

Optional callback function for additional processing.

If you do not provide a callback function, use NULL as the value of this parameter.

If you do provide a callback function, use the function pointer as the value of this parameter.

The callback function must adhere to the function prototype described in FILEREADCALLBACK Function.

L_VOID* pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs.

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.

If the additional parameters are not needed, you can pass NULL in this parameter.

pLOADFILEOPTION pLoadOptions

Pointer to optional extended load options. Pass NULL to use the default load options.

pFILEINFO 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.

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.

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.

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.

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

Value	Meaning
SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

Support for 12- and 16-bit grayscale images is only available in the Document and Medical Imaging toolkits.

The location of the image is specified as shown in the following simple illustration:

You must open the file and get a Windows file handle before calling this function. Redirected input (specified with L_RedirectIO) is disabled when this function is executing.

Before calling this function, you may need to get or set file information, such as the page number of a multipage file or the resolution of a PCD file. Refer to Getting and Setting File Information.

Notes:

More options are available in the LOADFILEOPTION structure.
You should never pass an uninitialized FILEINFO structure to this function.

Required DLLs and Libraries

LTFIL
File format DLLs
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

Win32, x64, Linux.