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symek

Brightest Point In Image

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hallo!

I wonder if there is a way in VEX to find brightest or darkest pixel in image without coding some fansy loop... I would like to know the range in pixel value from input before I apply some filter designed in VEX.

I don't need t6o know the positon - just info, that white point is at 17.4 and black at -3.6 (in floating point image for example)

thanks for help.

PS Mplay have a buttom which normalize the image range to 0 and 1. To do this it must know "bri" and "dark" to clamp or shift data.

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Hey there,

You can slurp the image into CHOPs and find the value there - probably with icmin() and icmax() or such. (type exhelp icmax in a Houdini textport). You might want to run it though the Mono COP first (if you want Luminance or Max Component) and just suck in the single resultant channel into CHOPs.

There might be other tricks too- I was kinda hoping that the new "minmax" filter that we see in Mantra 8.0 would have snuck into the Scale (downscale) filter menu then you could've scaled the image down to a single pixel and a "minmax max" would've sorted it out for you.

Hope this helps,

Jason

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thanks a lot,

chops won't be right solution a suppose, but I will try,

thanks a lot again!

PS On the other hand there should be some ways to manage arrays or get some basic info from plates, shouldn't be?

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PS On the other hand there should be some ways to manage arrays or get some basic info from plates, shouldn't be?

22595[/snapback]

Do you mean using the histogram view of the COPs Viewer ? Or the inspect toolbar?

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no, no,

I meant that function which gives you back a max or min value in some data, set, array (plate!) it is so common need that it should be implemented in VEX. Houdini must use such function all the time, for example in MPlay to automatic shift pixel for 0 to 1... I'm sure there is a way to get it :).

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no, no,

I meant that function which gives you back a max or min value in some data, set, array (plate!)  it is so common need that it should be implemented in VEX. Houdini must use such function all the time, for example in MPlay to automatic shift pixel for 0 to 1... I'm sure there is a way to get it :).

22627[/snapback]

Probably some nice access to the histogram would be able to provide a lot of this, no?

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Huh, I have the same problem. The basic idea is clear - Image COP and icmin/icmax expression functions. But I wonder how we can use ic* for "export" values from CHOPs to COPs. I'm asking because ic* work in the sand-box of the _current_ CHOP. And I can't use them as expression in my COPs.

So what can I do? :huh:

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Can you modify a channel in chops land to the be the value of icmin/icmax and then use the chop expression in cops to reference that channel?

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