On Sun, Nov 2, 2008 at 9:34 AM, Martin Nordholts <[EMAIL PROTECTED]> wrote:
> 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.
Yes, I see what you mean. Overall effect rather than mathematical relation.
>> 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.

I'm assuming that the separate layer modes will eventually separate
into their own files for reasons of speed, in which case this is
trivial to implement; request LAB color as the input format, apply
normal blending to A and B channels,
leave L channel unchanged from dest. I would certainly be willing to
do that when the time comes.

>> 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?
Colorized shading/lighting. The nice thing about grain merge and
extract is they have a very regular effect on intensity, which means
it is comfortable to eg. paint using Grain Merge on a Grain
Merge-moded layer.
If you start with a layer filled with color #808080 which is neutral:
Say you have colors #606060 and #a0a0a0, painting with one of those
will lighten the layer by 32; if you swap
colors you will be darkening the image by 32. Providing layer opacity
== 100%, that will result in a literal change of 32 to the underlying
image. That predictable symmetry helps.

Also, you may have noticed, Grain merge creates complimentary
colorings; eg Grain merging bright yellow #ffff90
makes the image brighter and yellower, Grain extracting the same
bright yellow makes the image darker and more blue.
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