I am interested in ebook reader for quite a while. But after trying with a 6-inch e-ink reader (Hanlin V3), I found it is almost useless to read normal PDF files on these machines. The font size is too small, while the page size is too wide.
So, a method to render PDF for these small devices is thought about and prototyped. The details are as follow:
1. Convert pdf to image. I use pdftoppm of xpdf. Such as:
pdftoppm -r 180 -f 245 -l 245 -gray -aa yes a.pdf a
2. Analyse the generated images. Break page into lines.
3. Divide each line long enough to two segments.
4. Rearrange the segments into a new page, with half of the width.
The example image before/after conversion is attached with the post. I think the result is acceptable.
The source code is attached with the post too. The source is released under the License of GPL v2/v3.
Basic Usage for version 0.4:
tar -xjf pi_0.4.tar.bz2
/* output goes in out directory */
img_dir_to_pdf.sh out chap-rf.pdf
2008-09-20 Huang Ying <firstname.lastname@example.org>
* Version: 0.8
* overall: Reorganize program in a more modular way.
* pi.image: Add unpaper support for scanned book
* pi.image: Add column compress support for scanned book
* pi.divide: Add simple divider for divide = 1
2008-08-30 Huang Ying <email@example.com>
* Version: 0.7
* pi.py: Add LRF output support.
* pi.py: Add TOC support for LRF output format
* pi.py: Add output rotate support.
* pdfminfo: Add pdfminfo to extract PDF information such as TOC,
title, author, etc.
* overall: Add initial windows support, thanks ashkulz of
2008-08-11 Huang Ying <firstname.lastname@example.org>
* Version: 0.6
* pi.py: Initial implementation of embolden.
* pi.py: Use norm coordinate in class Page and Line.
* pi.py: Add edge trimming support.
* pi.py: Add run pages mode.
* pi.py: Add page range support.
* pi.py: Re-work ImageOutput, split multi-page image.
* pi.py: Rotate during scale if approriate.
* img_dir_to_pdf.sh: Add color reduction support.
2008-05-17 Huang Ying <email@example.com>
* Version: 0.5
* pi.py: Detect word, and break lines at word end when possible.
* pi.py: Re-align the 'split line segment' (second half of line)
to align with the next line's indenting when appropriate. This
will make the first line indent and bullet items line up better.
* img_dir_to_pdf.sh: Added to convert from images to pdf.
2008-05-10 Huang Ying <firstname.lastname@example.org>
* Version: 0.4
* Some algorithms are configurable
* For some text may have problem, present both merged and divided
2008-05-03 Huang Ying <email@example.com>
* Version: 0.3
* Rewrite most algorithm in python except the image parsing (break
image into lines and characters). This will make it easier to
add new algorithm (hack).
* pi.py: Add some hacks to deal with equation and figure.
2008-04-29 Huang Ying <firstname.lastname@example.org>
* Version: 0.2
* Split lines in two equal halves or optional equal thirds or
* Separate output image into customizable page size
* Flex can be designate by user configuration
* Calculate DPI for each page
* Figure detecting and special processing. The figures are scaled
to page width and output twice, scaled and split.
2008-04-23 Huang Ying <email@example.com>
* Version: 0.1
Last edited by caritas; 09-20-2008 at 08:14 AM.
Reason: Version update