Friday, January 14 2011


[Update: significantly improved the Perl script]

The hardest part of my cunning plan isn’t “making a screensaver”; I think every OS comes with a simple image-collage module that will do that. The fun was in collecting the images and cleaning them up for use.

Amazon’s static preview images are easy to copy; just click and save. For the zoom-enabled previews, it will fall back to static images if Javascript is disabled, so that’s just click and save as well. Unfortunately, there are an increasing number of “look inside” previews (even in the naughty-novels genre) which have no fallback, and which are not easily extracted; for now, I’ll write those off, even though some of them have gorgeous cover art.

[Update: turns out it’s easy to extract previews for the “look inside” style; just open the thumbnail in a new window, and replace everything after the first “.” with “_SS500_.jpg”.]

A bit of clicking around assembled a set of 121 pleasant images at more-or-less the same scale, with only one problem: large white borders. I wanted to crop these out, but a simple pass through ImageMagick’s convert -trim filter would recompress the JPEGs, reducing the quality. You can trim off almost all of the border losslessly with jpegtran -crop, but it doesn’t auto-crop; you have to give it precise sizes and offsets.

So I used both:

crop=$(convert -trim $f -format "%wx%h%X%Y" info:-)
jpegtran -crop $crop $f > crop/$f

So, what does a collage of naughty-novel cover-art look like? Here are some samples (warning: 280K 1440x900 JPEGs): 1, 2, 3, 4, 5. [Update: larger covers, and full-sized]

These were not, in fact, generated by taking screenshots of the screensaver. It takes a long time for it to fill up all the blank spots on the screen, so I wrote a small Perl script that uses the GD library to create a static collage using the full set of images. If I desaturated the results a bit, it would make a rather lively background screen. For home use.