Add JPEG 2000 support to heif-enc

[torusrxxx]

heif-enc can now convert from JPEG 2000 files.

[farindk]

The question is, where do we stop :-)

For J2K it would also make sense to just copy over the bitstream (#1814).

[torusrxxx]

I consider those already imported by libheif, like JPEG 2000, and libwebp (libsharpyuv is from libwebp, may be add an option to find libsharpyuv from libwebp). Next, I am also interested in those with comparable quality to HEIF, like JPEG XL and OpenEXR, so an image quality and feature support comparison can be easily done. Not interested in adding support for obscure formats that just supports legacy SDR and not already imported by libheif.

It would be good to have a muxer API to copy the raw bitstream, but currently there is none. Maybe this example would demonstrate that API when it is supported.

[torusrxxx]

Is #750 declined? It seems that was able to copy the bitstream.

[farindk]

Is #750 declined? It seems that was able to copy the bitstream.

No, not declined. But adding such a thing is a deep architectural decision that has to be reviewed and designed thoroughly. The need wasn't urgent enough to justify the time needed.