The first image viewer for the WikiReader

Original The first image viewer for the WikiReader Editable
version 1 & 2 of 2

This is my first application for the WikiReader, the WikiReader Huge Image Viewer.

Images include a topo map of the Grand Canyon, a rasterized PDF page and several photos.



I was really attracted to the reflective display for outdoor reading. While books are great to read during down time, outdoor maps would be extremely useful. WRHI was designed to allow extremely fast zooming, compact representation of line art, and nearly unlimited resolutions. Just for fun it has a fractal dithering algorithm that looks a bit nicer and less orderly than Floyd-Steinberg.

Currently the largest image used has is been 6000 pixels wide. The WikiReader should be able to handle a million pixels wide, but the limiting factor is the python distill script for converting the image format. The format is optimized for simple decoding. It uses no compression to speak of, other than what is provided by quad trees. Compared to PNG, photos are roughly twice as large where as line drawings are a bit smaller. The WRHI file also contains a pre-rendered pyramid of zooms, and it is pretty remarkable that something so simple with all that extra data embedded could even come close to PNG.


  • Loads image files from a directory called images on the SD card
  • History button cycles image files
  • Search button zooms out
  • Random button zooms in
  • Touch to pan

This release is still a bit rough around the edges. I won't consider it done until it has a few more features:

  • Proper debouncing
  • File browser
  • Multi page documents
  • Touchscreen zoom
  • Nondestructive panning updates
  • Waypoint editing
  • Optional hinting for sharper text

If you'd like to hack on WRHI, you'll need WRDK.