Wanted: channel remapping with implicit colorspace conversion
Matthew Woehlke
mw_triad at users.sourceforge.net
Wed Sep 17 22:58:05 CEST 2008
Cyrille Berger wrote:
> On Wednesday 17 September 2008, Matthew Woehlke wrote:
>>> Yup. If you can make a curve that simulate a multiplication ;)
>> Um...? If I apply the brightness filter "2x + 0" (that performs a linear
>> mapping 0->0, 128->255), isn't that simply a straight-line curve filter
>> with those endpoints?
>>
>> What am I missing?
>>
>> A curve is merely an arbitrary function represented as a traditional
>> graph (and usually specified as an interpolated curve). Therefore, any
>> filter whose output is exactly one pixel for exactly one input pixel,
>> with no other (non-constant) inputs, can be represented as a curve. It
>> may have an inordinate number of points, but...
>
> Yes but most curve widget don't allow to all kind of curves (unless you add a
> lot of control points). For instance, I have never been able to make a
> correct gamma correction with a curve widget. But yes indeed multiplication
> is easily done since usually with only two points you get a line.
Indeed :-). Fortunately this shouldn't be needed for the things an
'import rawstudio adjustments' tool would need.
--
Matthew
Your eyes are weary from staring at the CRT. You feel sleepy. Notice how
restful it is to watch the cursor blink. Close your eyes. The opinions
stated above are yours. You cannot imagine why you ever felt otherwise.
-- Unknown
(found at http://goldmark.org/jeff/stupid-disclaimers/fun.html)
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