# type of feFunc*

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sun, 13 Jun 2010 15:05:36 +0200

Message-Id: <201006131505.37293.Dr.O.Hoffmann@gmx.de>
```Hello www-svg,

within the definition of the attribute type for the elements feFunc*
http://www.w3.org/TR/SVG11/filters.html#feComponentTransferTypeAttribute
there seem to be some variables in the formulas undefined.

Is my interpretation correct, that C and C' correspond to the relative
channel value the subelement represents?
Between 0 and 1? Colors have to be transformed to this range?
C before, C' after transformation?
For example for feFuncR this means the relative value of the red channel?

And what exactly is N?
My assumption is, that it is N = n. Is this correct?
At least the formulas for table and discrete look useful for
C from the interval [0;1)
For C = 1 the formulas have the problem,
that the v(n+1) for table does not exist and v(n) not for discrete.
k is one too large, there is a need to provide another formula for C=1
- something like: use formulas for [0;1) and v(n) for C=1 for table and
v(n-1) for C=1 for discrete.
For the table type this is only a formal problem, because (C-k/N) = 0
anyway, whatever  v(n+1) might be; the result is C' = v(n).
Nevertheless the formula should not contain the undefined v(n+1).
For the discrete type C'=v(n) for C=1 resulting in k=N is a problem,
because the v(i) are defined in such a way, that the last value is v(n-1).

Best wishes

Olaf
```
Received on Sunday, 13 June 2010 13:18:57 UTC

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