libjpeg

I have regenerated the tables in such a way as to build broader "dc"
tables. The new generator code is as follows, and the optimal table was
generated with a quality of 99.

#ifndef generate_universal_tables
long total = 0;
int has_over_15 = 0;

for( i = 0; i < 256; i++ )
{
if( freq[i] > 0 )
printf( "freq[%d] = %d\n", i, freq[i] );

total += freq[i];

if( i > 15 && freq[i] > 0 )
has_over_15 = 1;
}
printf( "total = %d\n", total );
printf( "has_over_15 = %d\n", has_over_15 );

for( i = 0; i < 256; i++ )
{
if( i < 16 || has_over_15 )
{
freq[i] += 1;
}
}
#endif

The change is commited in jcparam.c:1.2.

This was seemingly necessary to handle high quality values.

There was no objection, so I have committed this in jcparam.c 1.2.

For reference, I used the following additional code in
jpeg_gen_optimal_table() to try and make the resulting tables handle all
symbols.

Index: jchuff.c
===================================================================
RCS file: /cvsroot/libjpeg/libjpeg/jchuff.c,v
retrieving revision 1.1
diff -r1.1 jchuff.c
714a715,737
> #ifdef generate_universal_tables
> long total = 0;
> int has_over_12 = 0;
>
> for( i = 0; i < 256; i++ )
> {
> if( freq[i] > 0 )
> printf( "freq[%d] = %d\n", i, freq[i] );
>
> total += freq[i];
>
> if( i > 12 && freq[i] > 0 )
> has_over_12 = 1;
> }
> printf( "total = %d\n", total );
> printf( "has_over_12 = %d\n", has_over_12 );
> for( i = 0; i < 256; i++ )
> {
> if( i < 13 || has_over_12 )
> freq[i] += 1;
> }
> #endif
>

I developed a set of huffman by bulding a symbol histogram for the mandrill
image, adding one to every bucket in the histogram, and computing an
optional table for the resulting histogram. This table seems to handle all
possible symbols and presumably is at least vaguely efficient for images
like the mandrill. I'm not sure how great a choice it is overall. I will
attach a patch to incorporate it in 12bit mode.