University of Glasgow

Roderic Page

One of the many biggest challenges I\'ve faced with the
[BioStor](http://biostor.org) project, apart from dealing with messy
metadata, has been handling page images. At present I get these from the
[Biodiversity Heritage Library](http://www.biodiversitylibrary.org).
They are big (typically 1 Mb in size), and have the caramel colour of
old paper. Nothing fills up a server quicker than thousands of images.  
  
A while ago started playing with ImageMagick to resize the images,
making them smaller, as well as ways to remove the background colour,
leaving just black text and lines on white background.  
  

::: {style="text-align:center;"}
[![Before and after converting BHL
image](http://farm5.static.flickr.com/4145/5209041261_b50a80d1c4.jpg){width="425"}](http://www.flickr.com/photos/85456381@N00/5209041261/ "Before and after converting BHL image by Roderic Page, on Flickr")
:::

  
  
I think this makes the page image clearer, as well as removing the
impression that this is some ancient document, rather than a scientific
article. Yes, it\'s the Biodiversity **Heritage** Library, but the whole
point of the taxonomic literature is that it lasts forever. Why not make
it look as fresh as when it was first printed?  
  
Working out how to best remove the background colour takes some effort,
and running ImageMagick on every image that\'s downloaded starts putting
a lot of stress on the poor little Mac Mini that powers BioStor.  
  
Then there\'s the issue of having an [iPad viewer for
BHL](http://iphylo.blogspot.com/2010/09/bhl-and-ipad.html), and making
it
[interactive](http://iphylo.blogspot.com/2010/10/towards-interactive-djvu-file-viewer.html).
So, I started looking at the DjVu files generated by the Internet
Archive, and thinking whether it would make more sense to download those
and extract images from them, rather than go via the BHL API. I\'ll need
the DjVu files for the text layout anyway (see [Towards an interactive
DjVu file viewer for the
BHL](http://iphylo.blogspot.com/2010/10/towards-interactive-djvu-file-viewer.html)).  
  
I couldn\'t remember the command to extract images from DjVu, but I did
remember that Google is my friend, which led me to this question on
Stack Overflow: [Using the DjVu tools to for background / foreground
seperation?](http://stackoverflow.com/questions/4516901/using-the-djvu-tools-to-for-background-foreground-seperation).  
  
OMG! DjVu tools can remove the background? A quick [look at the
documentation](http://djvu.sourceforge.net/doc/man/ddjvu.html) confirmed
it. So I did a quick test. The page on the left is the default page
image, the page on the right was extracted using `ddjvu` with the option
`-mode=foreground`.  
  

::: {style="text-align:center;"}
![507.png](http://lh6.ggpht.com/_Gct8lVAxKqQ/TaheW7IW6SI/AAAAAAAAA4g/dQDbK5-qEnc/507.png?imgmax=800){border="0"
width="425"}
:::

  
  
Much, much nicer. But why didn\'t I know this? Why did I waste time
playing with ImageMagick when it\'s a trivial option in a DjVu tool? And
why does BHL serve the discoloured page images when it could serve
crisp, clean versions?  
  
So, I felt like an idiot. But the other good thing that\'s come out of
this is that I\'ve taken a closer look at the Internet Archive\'s
BHL-related content, and I\'m beginning to think that perhaps the more
efficient way to build something like BioStor is not through downloading
BHL data and using their API, but by going directly to the Internet
Archive and downloading the DjVu and associated files. Maybe it\'s time
to rethink everything about how BioStor is built\...


One of the many biggest challenges I've faced with the BioStor project, apart from dealing with messy metadata, has been handling page images. At present I get these from the Biodiversity Heritage Library. They are big (typically 1 Mb in size), and have the caramel colour of old paper.

Postagens de Rogue Scholar

BHL, DjVu, and reading the f*cking manual