- Mar 18, 2008
- Reaction score
In essence it is an arbitrary serialization of the elevation file header values. As such, I never took string values into account, so the name of the PNG file might be a problem. The idea is to have a space separated tag list in the "name=value" form, all in one line. The one-liner approach makes it more probable that editors that support PNG tags keep them alive during round-trips, like the "Comment" tag in GIMP. That same string is then simply written to a file.Does your format allow to be extended by additional tags (e.g. by adding more lines after the first)?
I might want to add more info, such as resolution level, latitude and longitude indices (or index ranges, if the PNG is a mosaic of multiple tiles), name of the PNG file, etc.
"ele2png" only takes that first line into account, so the "format" (a huge term for it, really) is indeed extendable.
Small note on the min/max/mean values there: my goal was to make the ele2png round-trip consistent, so that the chain ele->png->ele will produce exact binary matches on unedited PNGs. To achieve this, I had to store the ELE min/max/mean values as presented in the original file ("smin" etc.), but also as calculated in the conversion algorithm ("emin" etc.), which did not always match in my tests. Therefore I also stored the calculated values alongside the original values, and if the re-calculation on import yields the same values as the stored calculated ones, I used the originals to create the imported ELE header.