Optimizes quantization matrix by minimizing reconstruction error based
on quantized coefficients.
Feature is controlled by cinfo->trellis_q_opt; disabled by default.
Multiple trellis iterations may improve coding performance as Huffman
tables are updated with each iteration. In practice the benefit appears
to be very minimal
Trellis quantization is modified:
- to work on the configurable spectral range Ss to Se
- to optionally optimize runs of EOBs
- to optionally split optimization between 2 spectral ranges
In trellis quantization passes Huffman table code optimization is
modified such as to generable a valid code length for each possible
symbol by resetting frequency counters to 1 instead of 0
A new pass type trellis_pass is added. It defines a pass where trellis
quantization is done in the quantize_trellis() function.
Trellis quantization can be enabled by setting use_moz_defaults to 2 or
by using the -trellis option in cjpeg
Note that trellis does currently not work with scan optimization. Scan
optimization is disabled when trellis is enabled.
First implementation of scan optimisation as done by jpgcrush. Many
parameters are currently hardcoded which should be changed.
Implementation is missing for monochrome.
