On Friday, July 14, 2006 at 11:45,
Chuck Norcutt <olympus@xxxxxxxxxx> wrote:
> Sorry, not enough coffee yet I guess. But the point is that rounding
> will eventually cause some points that were previously distinct
> brightness levels to coalesce.
When compressed. But that is not a visual problem.
When expanded, the distinct levels have a greater distance between them, ie,
posterisation. That
usually is a visual problem
> Chuck Norcutt
>
> Ian Nichols wrote:
> > On 14/07/06, Chuck Norcutt <chucknorcutt@xxxxxxxxxxx> wrote:
> >>
> >>With only 256 integer brightness levels available in a JPEG if the
> >>brightness is increase by multiplying by, say, 1.5 then a brightness
> >>level of 100 becomes 150. But so does a brightness level of 101 become
> >>150.
> >
> > Eh? surely a brightness level of 101 would become 151 when multiplied by
> > 1.5 and clipped to an integer (would be 152 if using real maths and rounding
> > to nearest integer).
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