TonyB wrote:
> 
> Look into adding some way of adding sparkles when the color of the pixel
> surpasses a user-specified threshold.

John Beale has done sparkl01 which "add sparkle glint-type effects to a
TGA image"
http://www.best.com/~beale/gforge/

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Kari Kivisalo                                          www.kivisalo.net

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Chris Huff wrote:
> This sounds like the "highlight/midtone/shadow level adjustment" filter
> which is still in the "to-do" list. I would like to make a filter which

Catching up on the other threads here I found that you've already mentioned
this. Levels wouldn't be the same as highlight/midtone/shadow because it's
dynamic; it changes according to the darkest/brightest pixel. The
highlight/midtone/shadow will change the colour values regardless of the image.
I think this could make the levels process very useful since we don't have the
fast preview capabilites of image editing programs.

sig.

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On Fri, 28 Apr 2000 09:13:10 -0400, "TonyB"
<ben### [at] panamac-comnet> wrote:

>No. Because these kinds of lens flares usually make a sound when seen on TV.
>For example, the hero smiles and you see and hear the ding on his teeth.
>Knowwhatimean?

I understand now. Perhaps "glint" is a better word for what you are
describing.

Later,
Glen Berry


( Remove the "7" from 7no### [at] ezwvcom to email me. )

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In article <390A074A.1A022398@kivisalo.net>, Kari Kivisalo 
<kar### [at] kivisalonet> wrote:

> John Beale has done sparkl01 which "add sparkle glint-type effects to a
> TGA image"
> http://www.best.com/~beale/gforge/

I downloaded the source and will have a look at it. I already have a 
kind of sparkle effect working, but this could be helpful.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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In article <390A0B46.AEDCEB12@stud.ntnu.no>, Sigmund Kyrre Aas 
<as### [at] studntnuno> wrote:

> Catching up on the other threads here I found that you've already 
> mentioned this. Levels wouldn't be the same as 
> highlight/midtone/shadow because it's dynamic; it changes according 
> to the darkest/brightest pixel. The highlight/midtone/shadow will 
> change the colour values regardless of the image.
> I think this could make the levels process very useful since we don't 
> have the fast preview capabilites of image editing programs.

How about a filter that can take either 2 or 4 colors, if 2 colors, then 
it would adjust the colors of the image so the brightest is equal to the 
second color and the dimmest equal to the first. If 4 colors, it would 
override that "auto adjust" and adjust the image as if the two 
additional colors are the dimmest and brightest colors.
Is this what you want?

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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On Sat, 29 Apr 2000 10:56:20 -0500, Chris Huff
<chr### [at] yahoocom> wrote:

>In article <390A0B46.AEDCEB12@stud.ntnu.no>, Sigmund Kyrre Aas 
><as### [at] studntnuno> wrote:
>
>> Catching up on the other threads here I found that you've already 
>> mentioned this. Levels wouldn't be the same as 
>> highlight/midtone/shadow because it's dynamic; it changes according 
>> to the darkest/brightest pixel. The highlight/midtone/shadow will 
>> change the colour values regardless of the image.

You are only considering "auto levels" when you make that statement
about the levels control, if you are refering to the levels control as
implemented in Photoshop. It is also possible to supply parameters to
the levels dialog box to control the black point, white point, and
midpoint value (The midpoint value is similar to gamma, if not indeed
an actual gamma setting.) You can indeed manipulate the image in a
predermined manner, without relying on the computer to make some sort
of dynamic or automatic adjustment.

The GIMP has "levels" control, both auto and manual. It also seems to
be on par with the Photoshop levels control. Since the source is
available for the GIMP, it might pay to research the method used in
this program for inspiration.

PSP also has a similar function (histogram stretching? histogram
equalization?, not sure...), but it is different, and yields inferior
results.


Later,
Glen Berry

( Remove the "7" from 7no### [at] ezwvcom to email me. )

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Chris Huff wrote:
> 
> How about a filter that can take either 2 or 4 colors, if 2 colors, then
> it would adjust the colors of the image so the brightest is equal to the
> second color and the dimmest equal to the first.

Problem is you don't know the hue of the brightest/darkest pixel. That's why
I'm suggesting the bright/dark_tint. If the [darkest, brightest] colour is
[<.05,.1,.15>,<.9,.95,1>] and you simply set them to [<0,0,.05>,<1,.95,1>] it
will scale the rgb values differently. Although this might be useful, it will
almost certainly produce a tinted image.

"Auto Levels" in Photoshop does not preserve the hues of the darkest/brightest
pixel. It takes each colour component and scales them seperately, producing
[darkest, brightest] = [0,1], which IMHO is no good.

To get both these capabilities you could add keywords such as "absolute" and
"relative".

levels{ <dark>, <bright> relative}
If the brightest is <.9,.95,.93> the new value will be:
<.9,.95,.93>/.95*bright

If the darkest is <.1,.2,.3> the new value will be:
<0,.2,.3>*(1-.1)*dark
(Not sure of the math here. Idea is that 0.1->0 represents a 10% brightness
change)


levels{ <dark>, <bright> absolute}
If the brightest is <.9,.95,.93> the new value will be:
bright

If the darkest is <.1,.2,.3> the new value will be:
dark


sig.

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I think I get what you are saying...instead of adjusting the rgb values 
directly, you want to adjust the brightness of the colors?

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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Chris Huff wrote:
> 
> I think I get what you are saying...instead of adjusting the rgb values
> directly, you want to adjust the brightness of the colors?

Yes, and by allowing the parameters to be vectors you can adjust the colour
too. Just forgot something on the previous post: "Auto Levels" in Photoshop
would be equal to levels{ 0,1 absolute}. The setting I'd prefer would be
levels{1,1 relative}

Don't mind asking, I'd really like to see this feature. 

Cheers! sig.

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>In development:
>find_edges
>    The "cartoon-like" filter. It basically works, but still needs a lot
>of work.
>

I saw your test images of the find_edges-filter. That one is very useful,
although what _I_ personally miss is the ability to make the image look more
like a wire-frame-model. I have developed an algorithm (well... not
actually... actually not at all...) that might work: One takes the depth
information and interprets that as a graph of the two coordinate-axes, thus
implying a function depth(x, y). The natural place to put such a
"wire-frame-line" would be where this function have "breaks", kinda like
discontinuities. (For example in the intersection between two spherers.) If
one takes the gradient of depth(x, y) one obtains a 2-vector-field, and
taking the norm of that gives g(x, y). Taking the norm og the gradient of
that function, gives h(x, y). Where this h(x, y) takes on very large values,
we have a discontinuity in the image. Or so I think. I've never actually
tried it out... Could it be of interest?

Another post-process (or is it postprocess?): The ability to make a r/b or
g/r or whatever anaglyph for use with those 3d-glasses.

Simen.

>Does anyone have any suggestions for additional filters? I currently
>have these on the "to-do" list:
>highlight/midtone/shadow level adjustment
>color_function filter

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