mirror of
https://github.com/michaelrsweet/pdfio.git
synced 2024-12-27 05:48:20 +01:00
Compare commits
5 Commits
25834e07ef
...
0ab291a78b
Author | SHA1 | Date | |
---|---|---|---|
|
0ab291a78b | ||
|
cac6d4891c | ||
|
4f29ad89da | ||
|
9c04d1dc20 | ||
|
335472023e |
@ -2,7 +2,7 @@ Changes in PDFio
|
||||
================
|
||||
|
||||
|
||||
v1.3.2 - YYYY-MM-DD
|
||||
v1.3.2 - 2024-08-15
|
||||
-------------------
|
||||
|
||||
- Added some more sanity checks to the TrueType font reader.
|
||||
|
55
doc/pdfio.md
55
doc/pdfio.md
@ -118,20 +118,6 @@ 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
|
||||
|
||||
|
||||
Understanding PDF Files
|
||||
-----------------------
|
||||
|
||||
@ -286,40 +272,19 @@ startxref %startxref keyword
|
||||
%%EOF %End-of-file marker
|
||||
```
|
||||
|
||||
How a PDF File is Read
|
||||
----------------------
|
||||
|
||||
To read a PDF file, converting it from a flat series of bytes into a graph of objects in memory,
|
||||
the following steps might typically occur:
|
||||
1. Read the PDF header from the beginning of the file, checking that this is, indeed, a PDF
|
||||
document and retrieving its version number.
|
||||
3. The end-of-file marker is now found, by searching backward from the end of the file.
|
||||
The trailer dictionary can now be read, and the byte offset of the start of the cross-reference
|
||||
table retrieved.
|
||||
5. The cross-reference table can now be read. We now know where each object in the file is.
|
||||
6. At this stage, all the objects can be read and parsed, or we can leave this process until each
|
||||
object is actually needed, reading it on demand.
|
||||
8. We can now use the data, extracting the pages, parsing graphical content, extracting metadata,
|
||||
and so on.
|
||||
This is not an exhaustive description, since there are many possible complications
|
||||
(encryption, linearization, objects, and cross reference streams).
|
||||
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
|
||||
|
||||
How a PDF File is Written
|
||||
-------------------------
|
||||
|
||||
Writing a PDF document to a series of bytes in a file is much simpler than
|
||||
reading it—we don’t need to support all of the PDF format, just the subset
|
||||
we intend to use. Writing a PDF file is very fast, since it amounts to little
|
||||
more than flattening the object graph to a series of bytes.
|
||||
1. Output the header.
|
||||
2. Remove any objects which are not referenced by any other object in the
|
||||
PDF. This avoids writing objects which are no longer needed.
|
||||
3. Renumber the objects so they run from 1 to n where n is the number of
|
||||
objects in the file.
|
||||
4. Output the objects one by one, starting with object number one,
|
||||
recording the byte offset of each for the cross-reference table.
|
||||
5. Write the cross-reference table.
|
||||
6. Write the trailer, trailer dictionary, and end-of-file marker.
|
||||
|
||||
Reading PDF Files
|
||||
-----------------
|
||||
|
Loading…
Reference in New Issue
Block a user