Script Requests/Suggestions for gimp chat members

molly · **Joined:** Apr 07, 2010 **Posts:** 14182

I love the look of that flower Issabella.

trandoductin · **Posted:** Wed Jun 04, 2014 7:40 pm **(#22)**

Pegleg44,
try this script found here: http://gimpchat.com/viewtopic.php?f=9&t=10478

MareroQ · **Posted:** Thu Jun 05, 2014 10:26 am **(#23)**

ofnuts wrote:

MareroQ wrote:

Request new scripts/plugins
As for layers - only for Paths:
Select the Paths:
- All
- Invert
- Clear
- Reverse

What would "Select all" or "Clear" do? What is the difference between "Invert" and "Reverse" (by the way there is a "reverse-strokes" script in my collection).

ofnuts · **Joined:** Oct 25, 2010 **Posts:** 4758

If you shift-click on an eye icon, the click applies to all so its very easy to change the state of all paths, so All/None above are already there. Invert is easy to obtain the same way if there is only one Path that should be the opposite of the others.

Reverse would be a different animal but I don't see the purpose of reordering the paths? According to the doc of the Raise/Lower buttons "The position of a path in the list has no functional significance, so this is simply a convenience to help you keep things organized.". And if you reverse the order, the organization remains the same...

So that leaves us with toggling the visibility of several (but not all) paths together.

trandoductin · **Posted:** Mon Jun 09, 2014 11:25 am **(#25)**

is there a script-fu procedure to set white/black/mid gray points in levels?

I want to write a script that does this http://blog.patdavid.net/2011/06/getting-around-in-gimp-color-correction.html

by getting pixel values and comparing RGB values to see which points are whitest/darkest/grayest but can't see a procedure in script-fu for setting these white/black/mid gray points.

paynekj · **Posted:** Mon Jun 09, 2014 12:26 pm **(#26)**

trandoductin wrote:

is there a script-fu procedure to set white/black/mid gray points in levels?

I want to write a script that does this http://blog.patdavid.net/2011/06/getting-around-in-gimp-color-correction.html

by getting pixel values and comparing RGB values to see which points are whitest/darkest/grayest but can't see a procedure in script-fu for setting these white/black/mid gray points.

Maybe gimp-levels:

Attachment:

Untitled.png [ 30.1 KiB | Viewed 2286 times ]

trandoductin · **Posted:** Mon Jun 09, 2014 12:30 pm **(#27)**

paynekj wrote:

trandoductin wrote:

is there a script-fu procedure to set white/black/mid gray points in levels?

I want to write a script that does this http://blog.patdavid.net/2011/06/getting-around-in-gimp-color-correction.html

by getting pixel values and comparing RGB values to see which points are whitest/darkest/grayest but can't see a procedure in script-fu for setting these white/black/mid gray points.

Maybe gimp-levels:

Attachment:

Untitled.png

but how do you tell it like this is the white point and this is the black point and this is the gray point like the eye dropper that the user uses to choose these points?

Okay so I can set each Red/Green/Blue Channel in levels to black and white points, but what about the middle gray? what's the math behind gamma?

saulgoode · **Posted:** Mon Jun 09, 2014 1:40 pm **(#28)**

trandoductin wrote:

Okay so I can set each Red/Green/Blue Channel in levels to black and white points, but what about the middle gray? what's the math behind gamma?

You should double-check things, but I believe gamma can be calculated as follows:

Code: Select all

; gray-color is the RGB value of the gray point: (list red green blue)
; gray-pt is value of the particular channel's gray point
; black-pt is value of the particular channel's black point
; white-pt is value of the particular channel's white point

(define (gray-pt->gamma gray-color gray-pt black-pt white-pt)
  (let ((luminosity (+ (* (car gray-color) 0.2126)
                       (* (cadr gray-color) 0.7152)
                       (* (caddr gray-color) 0.0722) ))
        (range (- white-pt black-pt))
        (offset (- gray-pt black-pt)) )
    (/ (log (/ offset range))
       (log (/ luminosity range)) )))

trandoductin · **Posted:** Mon Jun 09, 2014 1:45 pm **(#29)**

thanks alot!
I'll try it see what i get.

ofnuts · **Joined:** Oct 25, 2010 **Posts:** 4758

I use Luca Dealfaro's scripts to correct colors. He uses curves, so his code would be a very good example.

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