Implementing PDF Plug in Features
Overview:
The PDF module enhances the input/output functionality in LEADTOOLS
by supporting a number of new powerful and complex file formats including:
PDF
PDF stands for Portable Document Format. It was developed by Adobe Corporation
to allow users to exchange and view their electronic documents in an easy
and reliable way , independent of the environment in which these documents
were created. A PDF file will look the same on the screen and in print
regardless of what kind of machine you are using or which software package
was used to create that file. One major advantage of PDF is that a large
document can be compressed small enough to download very quickly, and
still displays content as if you were looking at the original source such
as a book or magazine.
PDF is emerging as a powerful format for reproducing
documents over the web. Because of its high precision and accuracy in
representing text and pictures along with its "hyper" nature,
PDF is becoming a popular alternative to HTML and Postscript.
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
EPS stands for encapsulated PostScript .An EPS file is a PostScript language
program describing the appearance of a single page. Usually, the purpose
of the EPS file is 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 only a few limitations.
Occasionally, a customer may install two separate software applications
that use two different versions of the LEADTOOLS® PDF filter. If both
applications use the default PDF initialization directories, the runtime
library of the second application installed will overwrite the runtime
library of the first application installed. This can be avoided by setting
the PDF initialization directories using the L_SetPDFInitDir
function to some location other than the default. To get the current path
of the PDF initialization directories, call L_GetPDFInitDir.
Loading Capabilities.
The LEADTOOLS PDF plug-in has the following import capabilities:
|
1. |
Loads essentially all PDF 1.3 (Acrobat 4.x compatible)
files. |
|
2. |
Loads all PostScript Language Level 3 files. |
|
3. |
Loads any EPS file. |
The loading support is of course multi-page, where you can specify which
page to load from the file and to find the number of pages in a certain
document.
The plug-in gives the user a number of control options in order to customize
the resulting rasterized page. These options include:
|
1. |
Pixel depth. Valid values are 1,4,8 and 24 .The
default value for this control parameter is 24. |
|
2. |
Horizontal resolution in dots per inch with a default
value of 96. |
|
3. |
Vertical resolution in dots per inch with a default
value of 96. |
|
4. |
Ability to use either library installed fonts (fonts
installed by the plug in) or system fonts. The default value of this control
option is to use library installed fonts. |
|
5. |
Font anti-aliasing. Valid values are 1bit(no anti-aliasing)
, 2 and 4-bit anti-aliasing. The default value is 4, which gives maximum
anti-aliasing. |
|
6. |
Graphics anti-aliasing. Valid values are 1bit(no
anti-aliasing) , 2 and 4-bit anti-aliasing. The default value is 1. |
You can use the function L_GetPDFOptions
to get the default values for control options that are used when loading
a file. You can then use the function L_SetPDFOptions
to change the values for the control options.
Saving Capabilities.
Full multi-page write support is provided by this module for the PDF
format. This plug in lets you append, insert, replace or delete specific
pages in a PDF file created by 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. |
A number of new save format constants have been added to LEADTOOLS in
order to support types of files created by the PDF plug-in. For a list
of these, please refer to Formats of
Output Files..
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 L_GetPDFSaveOptions. To set
the options used when saving a PDF file, call L_SetPDFSaveOptions.
Distributing an application built using the PDF Module
The PDF plug-in needs some initialization files in order to work properly.
Before distributing an application built using this plug-in, you need
to setup the end-user machine with appropriate directories and files.
Please follow the steps below:
|
1. |
Create a main directory (referred to later as MAIN)
on the hard-drive to contain the files. For example "C:\Pdf". |
|
2. |
Create 3 subdirectories within this "MAIN"
directory, please name them "Lib, "Fonts", and "Resource". |
|
3. |
Copy the contents of the directory "Redist\Pdf\Fonts"
to the "Fonts" directory. |
|
4. |
Copy the contents of the directory "Redist\Pdf\Lib"
to the "Lib" directory. |
|
5. |
Copy the contents of the directory "Redist\Pdf\Resource"
to the "Resource" directory. |
|
6. |
Setup the registry configuration below: |
|
|
a. |
Create the following registry key: |
"HKEY_LOCAL_MACHINE\SOFTWARE\LEAD Technologies, Inc.\Pdf"
|
b. |
Under this key create a string value and give
it the name "GS_LIB". |
|
c. |
Now set the value data of the "GS_LIB"
value as follows: |
"MAIN\Lib;MAIN\Fonts;MAIN\Resource"
|
|
If MAIN stands for "C:\Pdf"
then this would become |
"C:\ Pdf\Lib;C:\ Pdf\Fonts;C:\Resource"