On Thu, 2011-02-03 at 10:42 +0100, Erik Auerswald wrote: <snip>
What I tried with some kind of success across an analog modem link years ago was the Differential X Protocoll Compressor (dxpc) http://www.vigor.nu/dxpc/ .
Just took a very quick look at this and it looks very interesting! Thanks for digging it out - John <snip> <snip> Had a chance to read a bit more and it looks quite nice. The only thing
On Thu, 2011-02-03 at 08:00 -0500, John A. Sullivan III wrote: that concerns me from their DESIGN document is this statement:
Image Compression
dxpc compresses images differently, depending upon their type:
For monochrome images with width-to-height ratios greater than 10 and heights less than or equal to 32, it transposes the images from row-major to column-major representation and applies a variant of the text-compression algorithm using 'h'-bit "characters," where 'h' is the image height. (Why would it do something so strange? Well... FrameMaker draws bitmapped text one line at a time, and this algorithm compresses the bitmapped text much more effectively than anything else I could come up with.)
For other monochrome images, it uses a variant of Group 4 FAX encoding.
For 8-bit color images, it uses a CharCache to hold previous pixel values and encodes them using technique 4.
For anything else, it sends the whole image, uncompressed.
I do not know how NX compresses images but it seemed like there were a wealth of settings (I know we found best results with 16m-png-jpeg) so this might be a big step backwards. I'll defer to those who know more than I - John