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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