ExeComp Binary @EX File v2

My wife bought me 100 years of National Geographic maps on an 8 CDROM set. The maps are great, but the image viewer it comes with is horrible. If anyone can help me extract the images I would be incredibly grateful. This is a personal project, so I don't have a lot of money for it, but would be willing to trade  services in kind in addition to a small honorarium.

The files have the extension ".@EX", begin with "ExeComp Binary @EX File v2" and appear to have embedded JFIF pyramids in them. I can send a sample to anyone interested in helping me but not post publicly as they are copyrighted.

Reverse engineering the file format#

I found a picdumper python script which extracts hundreds of tiles, however I haven't been able to view the results with anything. Taking Antarctica 1957 as an example and using the ngmaps viewer I can tell you that there are 6 levels of pyramids (some maps go as high as 8, maybe more). The first three levels are:

1: 337 x 270
2: 674 x 541
3: 1348 x 1083

or at least that's what I'm figuring based on taking screen dumps and cropping to the edge. The 3rd level screen dump is attached.

Picdumper has a comment about "otherwise images will be junk", so perhaps all that is needed to get the images out is to rework the logic in this section?

# this is the tricky part, to get the correct image
# we need the file posn before previous one!, that
# is we need to jump a position. Otherwise all images
# will be junk or of small resolution.

Another avenue to pursue is double encoding. Just before each JFIF block there are also what appear, to my untrained eye, PIC2 image headers embedded. Or maybe it's triple encoding because there's a PIC header also?

 

A work-around#

Courtesy of John Rausch I learned that I can export the maps by printing to a virtual pdf printer, and then converting that to an image and cropping to lose the whitespace. It's all pointy clicky and quite slow, but at least I can grab the maps of most interest to me, provided I already know what I'm looking for. I use pdfcreatorwhile John prefers TIFF Image Printer, citing better performance.

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date: 2009-12-15 tags: [projects] category: Projects