pdfio/doc/pdfio.md

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Introduction
============
PDFio is a simple C library for reading and writing PDF files. The primary
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goals of pdfio are:
- Read any PDF file with or without encryption or linearization
- Write PDF files without encryption or linearization
- Extract or embed useful metadata (author, creator, page information, etc.)
- "Filter" PDF files, for example to extract a range of pages or to embed fonts
that are missing from a PDF
- Provide access to objects used for each page
PDFio is *not* concerned with rendering or viewing a PDF file, although a PDF
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RIP or viewer could be written using it.
PDFio is Copyright © 2021 by Michael R Sweet and is licensed under the Apache
License Version 2.0 with an (optional) exception to allow linking against
GPL2/LGPL2 software. See the files "LICENSE" and "NOTICE" for more information.
Requirements
------------
PDFio requires the following to build the software:
- A C99 compiler such as Clang, GCC, or MS Visual C
- A POSIX-compliant `make` program
- ZLIB (<https://www.zlib.net>) 1.0 or higher
IDE files for Xcode (macOS/iOS) and Visual Studio (Windows) are also provided.
Installing pdfio
----------------
PDFio comes with a portable makefile that will work on any POSIX-compliant
system with ZLIB installed. To make it, run:
make all
To test it, run:
make test
To install it, run:
make install
If you want a shared library, run:
make all-shared
make install-shared
The default installation location is "/usr/local". Pass the `prefix` variable
to make to install it to another location:
make install prefix=/some/other/directory
The makefile installs the pdfio header to "${prefix}/include", the library to
"${prefix}/lib", the `pkg-config` file to "${prefix}/lib/pkgconfig", the man
page to "${prefix}/share/man/man3", and the documentation to
"${prefix}/share/doc/pdfio".
The makefile supports the following variables that can be specified in the make
command or as environment variables:
- `AR`: the library archiver (default "ar")
- `ARFLAGS`: options for the library archiver (default "cr")
- `CC`: the C compiler (default "cc")
- `CFLAGS`: options for the C compiler (default "")
- `CODESIGN_IDENTITY`: the identity to use when code signing the shared library
on macOS (default "Developer ID")
- `COMMONFLAGS`: options for the C compiler and linker (typically architecture
and optimization options, default is "-Os -g")
- `CPPFLAGS`: options for the C preprocessor (default "")
- `DESTDIR" and "DSTROOT`: specifies a root directory when installing
(default is "", specify only one)
- `DSOFLAGS`: options for the C compiler when linking the shared library
(default "")
- `LDFLAGS`: options for the C compiler when linking the test programs
(default "")
- `LIBS`: library options when linking the test programs (default "-lz")
- `RANLIB`: program that generates a table-of-contents in a library
(default "ranlib")
- `prefix`: specifies the installation directory (default "/usr/local")
Visual Studio Project
---------------------
> Note: I haven't yet added this...
The Visual Studio solution ("pdfio.sln") is provided for Windows developers
generates both a static library and DLL.
Xcode Project
-------------
There is also an Xcode project ("pdfio.xcodeproj") you can use on macOS which
generates a static library that will be installed under "/usr/local" with:
sudo xcodebuild install
You can reproduce this with the makefile using:
sudo make 'COMMONFLAGS="-Os -mmacosx-version-min=10.14 -arch x86_64 -arch arm64"' install
Detecting PDFio
---------------
PDFio can be detected using the `pkg-config` command, for example:
if pkg-config --exists pdfio; then
...
fi
In a makefile you can add the necessary compiler and linker options with:
```make
CFLAGS += `pkg-config --cflags pdfio`
LIBS += `pkg-config --libs pdfio`
```
Header Files
------------
PDFio provides a primary header file that is always used:
```c
#include <pdfio.h>
```
PDFio also provides content helper functions that are defined in a separate
header file:
```c
#include <pdfio-content.h>
```
API Overview
============
PDFio exposes several types:
- `pdfio_file_t`: A PDF file (for reading or writing)
- `pdfio_array_t`: An array of values
- `pdfio_dict_t`: A dictionary of key/value pairs in a PDF file, object, etc.
- `pdfio_obj_t`: An object in a PDF file
- `pdfio_stream_t`: An object stream
PDF Files
---------
PDF Values
----------
PDF Objects
-----------
PDF Streams
-----------