JNG Specification

Hello,

I'm about to write a photoshop plugin for the JNG file format (for the standalone jng files, not mng files). I'm very happy that such a file format exists (I'm particularly interested in the alpha channel support). Once I have finished the plugin, I'll release it as freeware (or perhaps donationware - but free).

I've got a license from Adobe, so I can use their "file format SDK" and I'm about to begin to write the plugin, but I still have two questions that came up to my mind:

1. If I understand correctly - jng exclusively uses Huffman Coding as the Entropy Encoding algorithm. Is this correct ?

2. The only jpeg specific "start of frame"-markers (SOFn) that may be used inside a JNG file are SOF0, SOF1 and SOF2. Is this correct ?

I read the latest versions of the JNG and the MNG specifications, and it seems to me that the JNG format limits the use of the jpeg stream according to the two questions, but I sometimes had the feeling not to be explicitly sure about these facts. I like these limitations, because they make my life a lot simpler, so I would be happy if you could clear my mind up a bit - so that I can be sure about that.

Kind regards
Tassilo Philipp


PS: If you are interested in the plugin, I'll contact you again once I have finished it.