As I’ve taken a two-day vacation pre-easter, I’ve gotten some more work done on my Wavelet Image Compression Library (and not played games as some of my colleagues were led to believe ;)).
Before this version all the subbands of an octave (i.e. HD, VD, and DD coefficients) were written as a single block in an interleaved manner. The changes I’ve made give each subband its own block, which increases the number of blocks, and thus allows for better and more fine-grained scheduling (which increases compression performance). Unfortunately, this led to a three times slower error estimation, which I then managed to cunningly avoid by computing the estimate for 3 blocks at a time.
Other changes include a more consistent behaviour for the -bpp command line switch, bug fixes to the scheduling where my accumulated fixed-point error estimates would overflow, and quite a few other things.
A experimental change was an exact error estimation, which I’ve then removed again as the code became unreadable, it was slow as hell, and didn’t actually help that much.
There is now a Darcs repository here (don’t try browsing there) from which you can get the current version and against which you can send me patches. You can also read my totally unfunny changelog entries if you need more information on the changes between versions.