In help for the unsharp mask, I read the following:

'To prevent color distorsion while sharpening, Decompose your image to HSV and
work only on Value.  Then Compose the image to HSV.  This is well explained at
gimpguru.org'

gimpguru.org does not describe this.  Can anyone explain what the help message
is about?

John.

John K. Herreshoff wrote:
> In help for the unsharp mask, I read the following:
> 
> 'To prevent color distorsion while sharpening, Decompose your image to HSV and
> work only on Value.  Then Compose the image to HSV.  This is well explained at
> gimpguru.org'
> 
> gimpguru.org does not describe this.  Can anyone explain what the help message
> is about?
> 
> John.

It seems pretty self explantory.  Go to Image/Mode and click on 
decompose.  Make sure the "Decompose to layers box" is checked.  Choose 
HSV and click okay.   You will get three layers, one for hue, one for 
saturation, and one for value. (Close the original image so you won't 
get confused.)  Select the value layer, and apply your sharpening to it. 
   When you are done, with that same layer selected, reverse the 
process.  go the Image/Mode and click on compose.  Again choose HSV and 
click okay.   You will get back your original image except that it will 
have been sharpened in the value component.

Leonard Evens wrote:

> John K. Herreshoff wrote:
>> In help for the unsharp mask, I read the following:
>> 
>> 'To prevent color distorsion while sharpening, Decompose your image to HSV
>> and
>> work only on Value.  Then Compose the image to HSV.  This is well explained
>> at gimpguru.org'
>> 
>> gimpguru.org does not describe this.  Can anyone explain what the help
>> message is about?
>> 
>> John.
> 
> It seems pretty self explantory.  Go to Image/Mode and click on
> decompose.  Make sure the "Decompose to layers box" is checked.  Choose
> HSV and click okay.   You will get three layers, one for hue, one for
> saturation, and one for value. (Close the original image so you won't
> get confused.)  Select the value layer, and apply your sharpening to it.
>    When you are done, with that same layer selected, reverse the
> process.  go the Image/Mode and click on compose.  Again choose HSV and
> click okay.   You will get back your original image except that it will
> have been sharpened in the value component.

Thanks!  That was simple enough, and it is a big improvement.

John.

Hi,

Leonard Evens wrote:
> John K. Herreshoff wrote:
> 
>> In help for the unsharp mask, I read the following:
>>
>> 'To prevent color distorsion while sharpening, Decompose your image to
>> HSV and
>> work only on Value.  Then Compose the image to HSV.  This is well
>> explained at
>> gimpguru.org'
>>
>> gimpguru.org does not describe this.  Can anyone explain what the help
>> message
>> is about?
>>
>> John.
> 
> 
> It seems pretty self explantory.  Go to Image/Mode and click on
> decompose.  Make sure the "Decompose to layers box" is checked.  Choose
> HSV and click okay.   You will get three layers, one for hue, one for
> saturation, and one for value. (Close the original image so you won't
> get confused.)  Select the value layer, and apply your sharpening to it.
>   When you are done, with that same layer selected, reverse the
> process.

what exactly does "reverse" mean? I tried this just now, but I'm getting
very strange "psychedelic" colors after combining the three layers back
to RGB (I applied "Unsharpen Mask" to the V channel).

Claus

Hi again,

Leonard Evens wrote:
> John K. Herreshoff wrote:
> 
>> In help for the unsharp mask, I read the following:
>>
>> 'To prevent color distorsion while sharpening, Decompose your image to
>> HSV and
>> work only on Value.  Then Compose the image to HSV.  This is well
>> explained at
>> gimpguru.org'
>>
>> gimpguru.org does not describe this.  Can anyone explain what the help
>> message
>> is about?
>>
>> John.
> 
> 
> It seems pretty self explantory.  Go to Image/Mode and click on
> decompose.  Make sure the "Decompose to layers box" is checked.  Choose
> HSV and click okay.   You will get three layers, one for hue, one for
> saturation, and one for value. (Close the original image so you won't
> get confused.)  Select the value layer, and apply your sharpening to it.
>   When you are done, with that same layer selected, reverse the
> process.  go the Image/Mode and click on compose.  Again choose HSV and
> click okay.   You will get back your original image except that it will
> have been sharpened in the value component.

here's an additional technique I've been using until now:

1. Select the entire image
2. Copy the selection into an alpha channel
3. Apply a "Filter > Find Edges" to the alpha channel
4. Apply a Gaussian Blur to the resulting alpha channel
5. Make a selection from this channel
6. Apply an "Unsharpen Mask" to the original (now partially
selected) image.

I posted this already in the GUG (Gimp User Group) mailing list,
after discovering this technique on the Internet. The results are
significantly better than merley applying "Unsharpen Mask", but
I'm going to check out the technique you described above, as well.

Claus

ccyrny wrote:

> Hi,
> 
> Leonard Evens wrote:
>> John K. Herreshoff wrote:
>> 
>>> In help for the unsharp mask, I read the following:
>>>
>>> 'To prevent color distorsion while sharpening, Decompose your image to
>>> HSV and
>>> work only on Value.  Then Compose the image to HSV.  This is well
>>> explained at
>>> gimpguru.org'
>>>
>>> gimpguru.org does not describe this.  Can anyone explain what the help
>>> message
>>> is about?
>>>
>>> John.
>> 
>> 
>> It seems pretty self explantory.  Go to Image/Mode and click on
>> decompose.  Make sure the "Decompose to layers box" is checked.  Choose
>> HSV and click okay.   You will get three layers, one for hue, one for
>> saturation, and one for value. (Close the original image so you won't
>> get confused.)  Select the value layer, and apply your sharpening to it.
>>   When you are done, with that same layer selected, reverse the
>> process.
> 
> what exactly does "reverse" mean? I tried this just now, but I'm getting
> very strange "psychedelic" colors after combining the three layers back
> to RGB (I applied "Unsharpen Mask" to the V channel).
> 
> Claus

When doing the Image > Mode > Compose, be sure that hsv is selected.  It
starts (defaults) to RGB, which will give the funny colors.

HTH.

John.

ccyrny apparently said,on my timestamp of 29/09/2005 10:27 PM:
>>
>>It seems pretty self explantory.  Go to Image/Mode and click on
>>decompose.  Make sure the "Decompose to layers box" is checked.  Choose
>>HSV and click okay.   You will get three layers, one for hue, one for
>>saturation, and one for value. (Close the original image so you won't
>>get confused.)  Select the value layer, and apply your sharpening to it.
>>  When you are done, with that same layer selected, reverse the
>>process.
> 
> 
> what exactly does "reverse" mean? I tried this just now, but I'm getting
> very strange "psychedelic" colors after combining the three layers back
> to RGB (I applied "Unsharpen Mask" to the V channel).

The very first time you do this, GIMP will assume the default
value for the type of "compose".  Which is RGB.  Make sure
that the *same* type you used for "decompose" (HSV, I've seen
also LAB recommended with L being sharpened) is selected
for the "compose".  Next time you do it, GIMP will remember
what you wanted and set it properly.  Until you clear all
filter memory.

-- 
Cheers
Nuno Souto
in windy Sydney, Australia
wizofoz2k@yahoo.com.au.nospam

Claus Cyrny apparently said,on my timestamp of 29/09/2005 10:40 PM:

> 
> here's an additional technique I've been using until now:
> 
> 1. Select the entire image
> 2. Copy the selection into an alpha channel
> 3. Apply a "Filter > Find Edges" to the alpha channel
> 4. Apply a Gaussian Blur to the resulting alpha channel

When you do this, how much?  IOW, how much blur does one need
to make something like this effective?  1? 5? 15? 50?

> 5. Make a selection from this channel
> 6. Apply an "Unsharpen Mask" to the original (now partially
> selected) image.

Thanks, I'll try this one.  Never used it.

-- 
Cheers
Nuno Souto
in windy Sydney, Australia
wizofoz2k@yahoo.com.au.nospam

John K. Herreshoff wrote:
> ccyrny wrote:
> 
> 
>>Hi,
>>
>>Leonard Evens wrote:
>>
>>>John K. Herreshoff wrote:
>>>
>>>
>>>>In help for the unsharp mask, I read the following:
>>>>
>>>>'To prevent color distorsion while sharpening, Decompose your image to
>>>>HSV and
>>>>work only on Value.  Then Compose the image to HSV.  This is well
>>>>explained at
>>>>gimpguru.org'
>>>>
>>>>gimpguru.org does not describe this.  Can anyone explain what the help
>>>>message
>>>>is about?
>>>>
>>>>John.
>>>
>>>
>>>It seems pretty self explantory.  Go to Image/Mode and click on
>>>decompose.  Make sure the "Decompose to layers box" is checked.  Choose
>>>HSV and click okay.   You will get three layers, one for hue, one for
>>>saturation, and one for value. (Close the original image so you won't
>>>get confused.)  Select the value layer, and apply your sharpening to it.
>>>  When you are done, with that same layer selected, reverse the
>>>process.
>>
>>what exactly does "reverse" mean? I tried this just now, but I'm getting
>>very strange "psychedelic" colors after combining the three layers back
>>to RGB (I applied "Unsharpen Mask" to the V channel).
>>
>>Claus
> 
> 
> When doing the Image > Mode > Compose, be sure that hsv is selected.  It
> starts (defaults) to RGB, which will give the funny colors.

Thanks! Now it works! Cool! ;-)

Claus
-- 
Web: http://home.arcor.de/ccyrny/ (mostly in German)

Hi,

Noons wrote:
> Claus Cyrny apparently said,on my timestamp of 29/09/2005 10:40 PM:
> 
>>
>> here's an additional technique I've been using until now:
>>
>> 1. Select the entire image
>> 2. Copy the selection into an alpha channel
>> 3. Apply a "Filter > Find Edges" to the alpha channel
>> 4. Apply a Gaussian Blur to the resulting alpha channel
> 
> 
> When you do this, how much?  IOW, how much blur does one need
> to make something like this effective?  1? 5? 15? 50?

I always use the GIMP default values.

>> 5. Make a selection from this channel
>> 6. Apply an "Unsharpen Mask" to the original (now partially
>> selected) image.
> 
> 
> Thanks, I'll try this one.  Never used it.

Admittedly, it's a bit complicated; therefore it would be
the best to make a Script-Fu for this, but I haven't dug
much into 'Scheme', yet.

Cheers,

Claus
-- 
Web: http://home.arcor.de/ccyrny/ (mostly in German)