David Gowers wrote:
> Hi,
> On Sat, Nov 1, 2008 at 11:06 PM, Martin Nordholts <[EMAIL PROTECTED]> wrote:
> Actually, I didn't understand  why you grouped them with Difference
> (even given your explanation of 'can produce completely different
> colors'); I would have grouped them with Overlay, since they both
> provide darkening ( on one side of 128) and lightening (on the other
> side of 128),

I had them grouped with Overlay for a while but ended up putting them
under Difference since Grain Extract can look very similar to
Difference. And from an aesthetic point of view it looks better to have
3 and 3-groups than 5 and 1-groups.

> I'm a bit puzzled as to why Multiply is paired thusly with Screen --
> Divide is closer to being the opposite of Multiply IMO (from a visual
> inspection div(mul(x)) and mul(div(x)) are closer to the original x
> than scr(mul(x)) or mul(scr(x)) )

One have to differentiate between mathematical similarities of the
blending formulas and the effect the modes have on the colours we
perceive. From this point of view Multiply pairs better when Screen than
with Divide.

Actually from this point of view Divide and Subtract should probably be
moved to the Difference category. They can produce completely new
colours as well. Addition doesn't really have a counterpart (Addition is
Linear Dodge in PS and GIMP has no Linear Burn counterpart).

The problem with introducing Linear Burn to GIMP is the name; what
should it be called? One alternative would of course be to call Addition
Linear Dodge instead.

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