> >Have you looked at jpeg2000 or similar for compression?

> JPG2000 is reputed to be lossless compression.


It's not lossless in all cases, but it does have a wavelet based
lossless mode.

The Pierian Spring says:

    http://en.wikipedia.org/wiki/JPEG_2000

There are several claimed advantages of JPEG2000 over the ordinary
JPEG standard:

Superior compression performance: At high bit rates, where artifacts
become nearly imperceptible, JPEG 2000 has a compression advantage
over JPEG by roughly 20% on average. At lower bit rates (e.g. less
than 0.25 bits/pixel for gray-scale images), JPEG 2000 has a much more
significant advantage over certain modes of JPEG: artifacts are less
visible and there is almost no blocking. The compression gains over
JPEG are attributed to the use of DWT and a more sophisticated entropy
encoding scheme.

Multiple resolution representation: JPEG2000 provides seamless
compression of multiple image components, with each component carrying
from 1 to 16 bits per component sample. With tiling, it handles images
of arbitrary large size in a single codestream.

Progressive transmission by pixel and resolution accuracy, commonly
referred to as progressive decoding and signal-to-noise ratio (SNR)
scalability: JPEG2000 provides efficient codestream organizations
which are progressive by pixel accuracy, by quality (SNR), by
resolution or by size. This way, after a smaller part of the whole
file has been received, it is possible to see a lower quality of the
final picture, the quality can be improved monotonically getting more
data from the source.

Lossless and lossy compression: JPEG2000 provides both lossless and
lossy compression in a single compression architecture. Lossless
compression is provided by the use of a reversible (integer) wavelet
transform.

Random codestream access and processing, also referred as Region Of
Interest (ROI): JPEG2000 codestreams offer several mechanisms to
support spatial random access or region of interest access at varying
degrees of granularity. This way it is possible to store different
part of the same picture using different quality.

Error resilience: JPEG2000 is robust to bit errors introduced by noisy
communication channels. This is accomplished by the inclusion of
resynchronization markers, the coding of data in relatively small
independent blocks, and the provision of mechanisms to detect and
conceal errors within each block.

Sequential buildup capability: JPEG2000 allows for encoding of an
image from top to bottom in a sequential fashion without the need to
buffer an entire image.

Flexible file format: The JP2 and JPX file formats allow for handling
of color-space information, metadata, and for interactivity in
networked applications as developed in the JPEG Part 9 JPIP protocol.

Side channel spatial information: it fully supports transparency and
alpha planes.

More advantages associated with JPEG 2000 can be referred to from the
Official JPEG 2000 page.


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