Implementing PDF Plug in Features

Overview:

The PDF module enhances the input/output functionality in LEADTOOLS by supporting a number of powerful and complex file formats including:

PDF (Portable Document Format), developed by Adobe Corporation, allows users to exchange and view electronic documents independent of their development environment. PDF files look the same on screen and in print regardless of the computer type or software package used to create them. One major advantage of PDF is that large documents can be compressed small enough to download very quickly, yet still display content as if you were looking at the original source such as a book or magazine. LEADTOOLS supports versions 1.2, 1.3, 1.4, 1.5 and 1.6 (read/write) of the PDF standard. To save a file as PDF version 1.4, include the ESO2_PDF_V14 flag in SAVEFILEOPTION.Flags2. To save a file as PDF version 1.5, include the ESO2_PDF_V14 flag in SAVEFILEOPTION.Flags2 and so on.
PDF/A LEADTOOLS supports the PDF/A subset of the standard, which contains only those features that are suitable for long-term archiving. To create a PDF/A file, include the ESO2_PDFA_PROFILE flag in SAVEFILEOPTION.Flags2.
PS (Postscript) is a simple interpretive page description language. Its primary application is to describe the appearance of text, graphical shapes, and sampled images on printed or displayed pages. Some of the page description and interactive graphics capabilities of the PostScript language include arbitrary shapes, painting operators, text fully integrated with graphics and sampled images derived from natural sources. Postscript is the language that most advanced laser printers use in order to render electronic information on a printed page.
EPS (Encapsulated PostScript) is a PostScript language program describing the appearance of a single page, usually intended to be embedded inside another PostScript language page description. The EPS file can contain any combination of text, graphics, and images, and it is the same as any other PostScript language page description with a few limitations.

Loading Capabilities.

The LEADTOOLS PDF plug-in has the following import capabilities:

1.	Loads essentially all PDF 1.3 (Acrobat 4.x compatible) through PDF 1.6 files.
2.	Loads all PostScript Language Level 3 files.
3.	Loads any EPS file.

The loading support includes multi-threading support and multi-page support, where you can specify which page or range of pages to load from the file.

LEADTOOLS gives the you a number of control options in order to customize the rasterized page. These options include:

1.	Pixel depth. Valid values are 0 (for auto-detect) 1, 4, 8 and 24. The default value for this control parameter is 24.
2.	Horizontal and vertical resolution in dots per inch with a default value of 96 by 96. It is recommended you change these to 300 if your application is loading the PDF files for recognition purposes (OCR or barcode for example) by using L_SetRasterizeDocOptions.
3.	Font anti-aliasing. Valid values are 1bit (no anti-aliasing), 2 and 4-bit anti-aliasing. The default value is 1, which gives the sharpest representation of the text in the file.
6.	Graphics anti-aliasing. Valid values are 1-bit (no anti-aliasing), 2-bit, and 4-bit anti-aliasing. The default value is 1.

You can use the function LFileSettings::GetPDFOptions to get the default values for control options that are used when loading a file. You can then use the function LFileSettings::SetPDFOptions to change the values for the control options.

You can also use LFile::GetRasterPdfInfo to get information specific to a PDF file, such as its original bits/pixel, compression, size and resolution

Saving Capabilities.

Full multi-page write support for the PDF format is provided by this module. This plug in lets you append, insert, replace or delete specific pages in a PDF file created with LEADTOOLS.

The plug-in gives you a wide range of control options for the resulting image data in terms of compression, including:

1.	No compression
2.	Compressed using CCITT Group 3, 1 dimension. For 1-bit images.
3.	Compressed using CCITT Group 3, 2 dimensions. For 1-bit images.
4.	Compressed using CCITT Group 4. For 1-bit images.
5.	JPEG compression and YUV 4:4:4 color space loss-less. Bits per pixel: 8 for grayscale, 24 for color.
6.	JPEG compression and YUV 4:2:2 color space. Bits per pixel: 8 for grayscale, 24 for color.
7.	JPEG compression and YUV 4:1:1 color space. Bits per pixel: 8 for grayscale, 24 for color.

The plug-in also gives you control over the type of encoding to be used in order to change compressed image data into a text format .The text encoding techniques include:

1.	No text encoding at all.
2.	Use ASCII 85 text encoding algorithm.
3.	Use ASCII HEX text encoding technique.

A number of new flags have been added to the SAVEFILEOPTION structure, in order to specify which type of text encoding to use when saving. For more information, please refer to that structure for more details. In addition, LEAD provides the FILEPDFSAVEOPTIONS structure to let you control the security of and access to the PDF file that is saved. These include user and owner passwords, encryption options, and the capabilities the user of the resulting PDF document will have. To determine the current options used when saving a PDF file, call LFileSettings::GetPDFSaveOptions. To set the options used when saving a PDF file, call LFileSettings::SetPDFSaveOptions.

Distributing an application built using the PDF Module

LEADTOOLS provides support for PDF loading and saving through two DLLs: LFPDF?.dll and LTPDFENGINE.dll.

LFPDF?dll is the file filter for PDF support in LEADTOOLS. LTFIL which contains the LEADTOOLS raster images load and save support, will load this dll dynamically when PDF files are loaded or saved. This is the normal behavior for LEADTOOLS support for any file format.

LTPDFENGINE.dll is the PDF runtime DLL. This DLL is never referenced directly by the LEADTOOLS Raster PDF file filter, instead it is loaded dynamically and out of process by the filter.

By default, the LEADTOOLS installer will copy this DLL next to the filter (in the Bin\CDLL\Win32, Bin\CDLL\x64, Bin\CDLLVC10\Win32 and Bin\CDLLVC10\x64 folders) and the filter will look for the engine DLL in the same folder it is located (default location).

In some cases, you can share the same copy of LTPDFENGINE.dll between different applications. In this case, you can copy LTPDFENGINE.dll to a fixed directory and pass the name of this directory to L_SetPDFInitDir. From this point on, LEADTOOLS will use this value to locate and load LTPDFENGINE.dll.

In addition to these DLLs, LEADTOOLS might require the use of other DLLS when saving PDF files depending on the compression used. For more information, refer to Files To Be Included With Your Application.