RyōTa SimaMoto (Sonntag, 8. November 2009, 18:51):

Some formulas are reformed.
* Multiplication signs '*' are all removed because they can be omitted in almost regular mathematic expressions.

But sometimes the expression is more readable with a "*", IMHO: "256 * I" vs. "256I"

Style of formula is changed to TeX's mathematical display mode.

There are some braces left over from \frac. BTW, why did you replace "\frac" with "\over"? (I'm TeX/LaTeX beginner...)

Can this reformation be acceptable for all users?

I wonder if we shouldn't make some more fundamental changes:

It looks like layer/blend mode formulas are typically expressed using values in the range 0..1. This makes them independent of the color depth and simplifies the equations (e.g. "E = M * I" for the multiply mode).

If we just want/need to explain layer modes without describing any internal details of how to compute the "real" values, we should consider switching to the - as far as I see - common way to describe layer/blend modes.

I found some nice links here: http://lists.xcf.berkeley.edu/lists/gimp-developer/2009-October/023624.html

Ulf

2009/11/17 Ulf-D. Ehlert :

But sometimes the expression is more readable with a "*", IMHO: "256 * I" vs. "256I"

There are some braces left over from \frac. BTW, why did you replace "\frac" with "\over"? (I'm TeX/LaTeX beginner...)

Then I will insert \times multiplication sign. Please check the bug#601156 (attachment #148040). I'm rarely familiar with LaTeX, so I used plain TeX. It is easy to get the TeX BOOK on the Net.

I wonder if we shouldn't make some more fundamental changes: ...

I approve your idea. Will it be like this?: http://www.geocities.jp/ss2pxd1c/snapshots/layermodesU.la.pdf

-=-=-=-=-= SimaMoto,Ry?Ta

http://code.google.com/p/gimp-doc-ja/

SimaMoto, RyōTa (Mittwoch, 18. November 2009, 17:02):

I approve your idea. Will it be like this?: http://www.geocities.jp/ss2pxd1c/snapshots/layermodesU.la.pdf

Yes, assuming these formulas are correct, of course. ;-)

No feedback from anybody else? (What does it mean - good / bad / don't care?)

Ulf

Andy Pitonyak (Sonntag, 22. November 2009, 21:50):

When I see something like "A x B", I do not assume that A is multiplied by B; I assume that a cross product will occur. I will concede that 2A is more readily understood as 2 times A than AB is A times B, but, for anyone that understands the math, that one particular notation may prove unsettling.

Hmm, and I thought we should even replace "E = min((M + I),255)" with "E = M + I" (plus a footnote or so) because the first formula might be too complicate for some users... ;-)

I will concede that in different places and at different levels, both the cross product (like an x) and dot product (a single dot) symbols are used to represent multiplication. I usually only see this in very introductory level material.

Using the "x" (ISO-8859-1 / Unicode 0xD7) as "simple" multiplication sign seems to be a standard for texts created (or used) by computer programs. (Most programmers would probably use the familiar "*", and you would never find it e.g. in a German math book, though.) Same with the division sign (÷) -- a kind of standard(?), but it seems that nobody uses it.
(If I remember correctly we used this division sign at school when we learned how to divide integers...)

If you do choose to use a symbol to represent multiplication I strongly recommend extra text explaining this with perhaps a foot note when this format is used.

We should get rid of any problems if we use the \cdot macro, which produces the usual multiplication symbol.

I recommend against this usage. I do not expect to ever see it in cases such as 1-2(1-1/2), or (A-B)(C+D).

These are good examples where we could easily omit any multiplication symbol. But a formula like "256I" (with 'I' in italics) looks ugly, and e.g. "E = MI" may look a bit weird outside the math lessons.

So my suggestions is that we use \cdot if the formula looks better with a multiplication symbol, and don't use any multiplication symbol otherwise.

Ulf