Another good site to see how this effect work over LAB channel with examples and step by step.

  http://www.outbackphoto.com/workflow/wf_81/essay.html
   

Am Friday 09 February 2007 schrieb Juanma Font:
[bugs.kde.org quoted mail]
What is the interest of this plugin? I can reproduce the same thing and better 
with digikam. I can't see the use?

Gerhard

> [bugs.kde.org quoted mail]
> What is the interest of this plugin? I can reproduce the same thing and
> better with digikam. I can't see the use?


No. You cannot reliably reproduce the same thing in Digikam because in
Digikam you cannot operate in L*a*b space. And while I think such
specialized plugin (Velvia effect) wouldn't be very useful but
possibility to operate in L*a*b would be *very* welcome.

Am Saturday 10 February 2007 schrieb Mikolaj Machowski:
[bugs.kde.org quoted mail]
Sorry for my ignorance about L*a*b space. 
My comment originated from taking the examples on the internet and using 
digikam to reproduce the effect. With a bit of whitebalance, intensity and 
U-mask I got very quickly the (visually) same results.

Gerhard

A plugin that can reproduce the velvia effect will be very apreciated by a lot of photographers (I'm an amateur photograph and this effect is very used at gimp by photographers but whith the limitation of 8 bits).

   Of course, if we can operate at LAB space we can get the same ,but we need technical information about the process and, of course, this is something that many people don't have.

   

Nota : digikam use lcms to handle color space. It's easy to toggle on LAB color space to perform color adjustement.

Gilles Caulier

I agree with #5. It's always nice to have another more specialized color plugin.

I did some more testing with the Gimp eg-color saturation tool (which is supposedly the equivalent of velvia), and I changed my mind (see #4). My tests with the small images from the referenced websites did not reveal the power of the plugin. Now with high resolution images I can appreciate the worth of such a plugin, it is very desirable indeed.

Gerhard

hey guy,

I have take a look into the vivid saturation gimp plugin : it's a script scheme  plugin...

It's very simple gerhard. Look like the code is a few line :

(define (script-fu-vivid-saturation inImg inDrw inAmount)

  (let* (

	 (amount (/ inAmount 100)))

    (gimp-image-undo-group-start inImg)

    (plug-in-colors-channel-mixer TRUE inImg inDrw FALSE (+ 1 amount amount) (- amount) (- amount) (- amount) (+ 1 amount amount) (- amount) (- amount) (- amount) (+ 1 amount amount))

    (define (spline)
      (let* ((a (cons-array 8 'byte)))
	(set-pt a 0 0 0)
	(set-pt a 1 63 60)
	(set-pt a 2 191 194)
	(set-pt a 3 255 255)
	a))
  
    (gimp-curves-spline inDrw 0 8 (spline))

    (gimp-image-undo-group-end inImg)
    (gimp-displays-flush)
    )
  )


It's use color mixer and curve tools. both are include in digiKam and of course support 16 bits color depth (unlike gimp do!)

Gerhard, try to reproduce the plugin using digiKam tools by hand and give me your viewpoint. From a developper point, i can do it in 5 minutes (:=)))

Gilles

 Gilles Said 
    "From a developper point, i can do it in 5 minutes"

   Ohhhhh.... this is a very good new !!!!

   Any developer with five (or ten.... or thirty....) minutes ?

   Please....please....  I promise sent two beers ¡¡¡¡

  Regards

Am Monday 12 February 2007 schrieb Gilles Caulier:
[bugs.kde.org quoted mail]
Hi Gilles, 
I tried it with the mixer [took me a while to get back into the scheme syntax, 
it should be called script-fou :-)] and it works well. 
What I could not verify it the spline function (the channel mixing is applied 
in a contrast enhanced manner: more inthe highlights, less in the shadows). I 
think I cannot reproduce it manually, that must be done under the hood. But 
even without spline the result looks quite promissing.

These are the values I tried (20% accentation):
# Channel Mixer Configuration File
CHANNEL: BLUE
PREVIEW: true
MONOCHROME: false
PRESERVE_LUMINOSITY: false
RED: 1.400 -0.200 -0.200
GREEN: -0.200 1.400 -0.200
BLUE: -0.200 -0.200 1.400
BLACK: 1.000 0.000 0.000

In gimp I needed only 6% to achieve the same effect. I believe the rest comes 
through the contrast amplification.

my 10

Created attachment 19909 [details]
Experimental Velvia tool for image editor

Gerhard, it don't work properlly. You need to adjust patameter in Channel
Mixer.

The new option is in Filter menu. Just compile and install patched image plugin
core.

Gilles

Created attachment 19910 [details]
Velvia tool : Second version of the patch

This new verion work fine exactly like gimp (:=))

Of course the amount parameter is harcoded to 10.

Gerhard, feel free to adapt and improve this code, for example to provide a
Amount adjustment setting in a dialog. It's easy to do and you have a lot a
plugins source code in digikam to take inspiration (:=)))...

My 10cts €...

Gilles

Gerhard, 

The Danamic Range Extender script-fu is also very easy to backport into digiKam...

Look here :

http://www.trsqr.net/photokit/dre.html

Gilles

SVN commit 640901 by cgilles:

digikam from trunk : Solarize plugin is now a "Color Effects" tools pack witch include :

- Solarize Photograph.
- Simulate Velvia Color Film (Vivid Saturation).
- Simulate Neon light.
- Color Edge detection.

Future others Color algorithm will be add to this plugin. No need to create new one.

BUG: 141439

 M  +1 -1      digikamimageplugin_solarize.desktop  
 M  +463 -43   imageeffect_solarize.cpp  
 M  +59 -8     imageeffect_solarize.h  
 M  +3 -3      imageplugin_solarize.cpp