On Sat, Oct 15, 2005 at 09:40:26PM +0200, Felix E. Klee wrote:

At Fri, 14 Oct 2005 13:48:59 +0200, Felix E. Klee wrote:

I want to bend an grayscale image's gray level curve so that three input levels are turned into three output levels. For all six levels I have the precise values, for example acquired with the color picker tool.

So far, I've played with the tools in the right mouse button menu "tools / color tools", but unsuccessfully.

Any suggestions?

Being desperate, I fired up Micrografx Picture Publisher 5.0a, an old Win 3.1 program. It's capabilities for doing color correction are quite powerful, even when measured by today's standards. Similarly to the Gimp it offers a dialog box for adjusting color curves, and in addition to manipulating points on the curve with the mouse, one can enter point coordinates with the keyboard. This is perfect for solving the problem I described in my original posting.

Now, although Picture Publisher 5.0a is still a very nice tool, it does have a number of disadvantages, especially when it comes to handling modern file formats. Also, it - of course - doesn't run natively under LINUX. That's why I try to do more and more tasks with the Gimp, and that's why I still would like to hear about a simple solution for my problem with the Gimp.

to be honest, i thought about the levels tool when i first read this but i really do not know so much about what it is you want.

have you tried the levels tool? perhaps you could show via images what it is you are looking for?

maybe what you need is that a plug-in be written. even this works better if there is a paper or a presentation at one of those graphics meetings -- anything like that would help. there is a python call to the levels tool:
pdb['gimp-levels'](drawable, channel, low-input, high-input, gamma, low-output, high-output)

and i have an example of elementary use of the tool here: http://carol.gimp.org/gimp2/photography/clarity/ i just had a strong feeling that you wanted more.

carol

On 10/15/05, Felix E. Klee wrote:

At Fri, 14 Oct 2005 13:48:59 +0200, Felix E. Klee wrote:

I want to bend an grayscale image's gray level curve so that three input levels are turned into three output levels. For all six levels I have the precise values, for example acquired with the color picker tool.

Any suggestions?

Being desperate, I fired up Micrografx Picture Publisher 5.0a, an old Win 3.1 program. It's capabilities for doing color correction are quite

Now, although Picture Publisher 5.0a is still a very nice tool, it does have a number of disadvantages, especially when it comes to handling modern file formats. Also, it - of course - doesn't run natively under LINUX. That's why I try to do more and more tasks with the Gimp, and that's why I still would like to hear about a simple solution for my problem with the Gimp.

This sounds interesting, although I wish I knew what a gray level curve was (is it that histogram-like thing that you get on some cameras that shows you how much the value is in the various regions of the picture left to right?).

If there is a numerical formula or procedure you can think of where I can give you any random pixel, and you can use that pixel's value, (and maybe position or some other data that should be obtainable from that pixel), the three input values, and three output values, I can imagine a plug-in being created. I can't think of any such thing, unfortunately. Otherwise, my next guess would be resorting to a bogo-sort-like "algorithm", which would take years to come up with a result for one image. I'm sure someone else can do better, obviously.

Is there a display function/filter/tool/plug-in/script-fu/etc for the grey level curve in GIMP though?

IIRC, in GIMP 1.x, there was a plugin that would, at the least, I believe, normalize the grey curve (although I may be wrong)... appraently the plug-in is no longer necessary for it's purpose in GIMP 2.x, although I don't know.

What about the Layer | Colour | Curves dialgoue thingie (Colour | Curves in GIMP 2.3.4)?

--
~Mike
- Just my two cents
- No man is an island, and no man is unable.

I assume you played around with the curve tool? Although you can't enter precise values, the values are displayed in the top left corner, so it's easy enough to get the result you want.

More here: http://gimp-savvy.com/BOOK/index.html?node61.html http://docs.gimp.org/en/ch07s05s07.html

On Fri, 14 Oct 2005 13:48:59 +0200 "Felix E. Klee" wrote:

I want to bend an grayscale image's gray level curve so that three input levels are turned into three output levels. For all six levels I have the precise values, for example acquired with the color picker tool.

So far, I've played with the tools in the right mouse button menu "tools / color tools", but unsuccessfully.

Any suggestions?