David Gowers wrote:
> On Sun, Nov 2, 2008 at 12:02 AM, Martin Nordholts <[EMAIL PROTECTED]> wrote:
>> 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.
> No, that's what I was saying -- from VISUAL inspection.I didn'c check
> the numbers, just how it looked when I painted in div mode then
> multiply mode with same color, etc..

I understand what you mean now. We are not doing the same kind of paring
though. You are pairing layer modes that are cancelling each other out
while I am paring layer modes that give opposite effects on lightness.
To convince yourself of that Multiply pairs with Screen in the latter
case, create an image with two layers, one with a vertical
black-to-white gradient and the other with a horizontal black-to-white
gradient (so that all possible combinations of channel intensities are
blended). Then examine the result of having the top layer first set to
Multiply and then to Screen.

In the former case you are correct, Divide cancels Multiply. I.e.
putting a copy of a Multiply layer on top of itself with the Divide
layer modes yields no change at all to the end composite (in absence of
rounding and clamping).

> Linear Burn is exactly a reversed Subtract, yes? that is,
> result = dest - (1-src)
>  rather than
> result = dest - src
> ?

Yes exactly, Linear Burn is

  result = dest - (1 - src) = dest + src - 1

> * Color mode is markedly inferior to PS Color mode (because it uses
> HSL, rather than LAB colorspace, the transference is not only of color
> data but some intensity data.). It's important to include some Color
> mode, however if we can get Color mode working in LAB space, we should
> probably show that by default and hide old style Color mode.

I agree, the current Color mode and friends can give pretty unexpected
results. Personally I don't think I will put much effort in that in the
near future though.

> Personally, only about 7 of the layer modes have any use to me:
>    normal dissolve difference multiply divide grainMerge grainExtract

Interesting, what do you use Grain extract and Grain merge for?

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