It's not very comparable to PNG, since they're designed for different types of imagery. I know currently Trigrad cannot handle text at all. In regards to your other comment, it's currently definitely worse than JPEG for vector imagery.
However, it handles gradients amazingly. A full colour gradient such as [0] can be made a tenth of the size since only ~500 samples are really needed.
However, it handles gradients amazingly. A full colour gradient such as [0] can be made a tenth of the size since only ~500 samples are really needed.
[0] http://i.imgur.com/QzW0z2O.png