On 2009-10-24, Ilya Zakharevich <nospam-ab...@ilyaz.org> wrote:

> So what about the following icon: take some background color in good
> contrast with all gray20, gray128, and gray245.  On this background, plot
> the graph of F(20,L) in gray20, etc.  One gets an icon with 3 graphs.

Forgot to explain why values 20 and 245 (gray128 is more or less
self-explanatory: it is a "neutral" [= "no-change to what is below
it"] color for a lot of modes, and plotting a diagonal gray128 graph
for these modes is a major hint)...

A lot of modes involve clamping of levels outside [0..255] range.  As
a result, graphs describing the effect of white and black are the same
for a lot of modes.

For example, "hard light" and "grain merge" modes give the same effect
when the top level has only black, gray128, and white.  To
disambiguate, one should better replace black and white by similar
near-white and near-black grays.

Thinking about it more: maybe the graphs would look more
distinguishable if near-white and near-black are in fact 2/3 of the
way between gray128 and white/or/black.  Then the plots would
correspond to gray40, gray128, gray215.

Ilya

P.S.  Another visual aid: scanning internet for recipes of image
      manipulation, it looks like people do not realize that instead
      of combining two copies of a layer in "Multiply" mode, one could
      as easy use (non-destructive) gamma=0.5.

      So one may want to plot on the same graph ALSO the curve
      equivalent to combining image with itself.  Then one needs to
      have 5 contrasting colors: background, 1 for effect-of-duplication,
      gray40, gray128, gray205.

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