Posted: Tue Jul 12, 2011 6:12 pm Post subject: Generate gradient map from image?
Hi!
Is there a way of making a custom gradient map from an image?
If it's not clear what i mean:
AFAIK a gradient map assigns colours to pixels according to their brightness. I practically want the reverse of this: Have a gradient map generated with the average colour of every pixel that has the same brightness in an image or part of an image.
I would hope to use this in portrait retouching, to get control of skin tones. If i try to make a gradient map manually, i never end up with realistic skin tones.
Joined: 20 Dec 2008
Posts: 710
Location: Oklahoma PS Version: photoshop cs5 OS: win7 pro 64 bit, i7-3.2g, GTS 450,
Posted: Tue Jul 12, 2011 7:18 pm Post subject: Re: Generate gradient map from image?
hi
first your a lot better than me.. but maybe i have an idea..... iam still learning about gradients..lol anyway
1. make a swatch of the image you want that will have the range of color you want
note: you may be able to find some swatches of skin color that might work...
2, then create a new color gradient...
3. set you points in the gradient editor
4. then using the eyedropper sample the colors in the swatch... you should see it set in the gradient scale....
then save the gradient...
I am not sure if that is what you want or if it will work for what you have in mind.. but it an idea.... i tried... let me know...
Alcazar wrote:
Hi!
Is there a way of making a custom gradient map from an image?
If it's not clear what i mean:
AFAIK a gradient map assigns colours to pixels according to their brightness. I practically want the reverse of this: Have a gradient map generated with the average colour of every pixel that has the same brightness in an image or part of an image.
I would hope to use this in portrait retouching, to get control of skin tones. If i try to make a gradient map manually, i never end up with realistic skin tones.
Posted: Wed Jul 13, 2011 4:26 pm Post subject: Re: Generate gradient map from image?
Hi! Thank you!
However this doesn't solve the basic problem...
i would have a set of nice colours to chose from, but i still wouldn't know where exactly to place the points on the gradient editor to match them to the corresponding brightness.
Or am i getting you wrong?
Micha
Joined: 05 Mar 2003
Posts: 3987
Location: Cheltenham, UK
Posted: Wed Jul 13, 2011 5:54 pm Post subject:
Hi Alcazar, welcome to the forum, a gradient mask for skin tone is usually generated from a set range of values (depending upon your technique) on either a set given range of values or sampled from the image (my preferred way), with blending mode set as colour and the opacity set to suit.
There are many ways to unify skin tones and blotchy skin and there are even more ways to unify slightly more saturated or uneven skin tones. I can think of more appropriate techniques but they may not be applicable to you, so I hesitate.
If you have an example of the type of effect that you are attempting to create, by all means post it. _________________ If life serves you lemons, make lemonade!
a gradient mask for skin tone is usually generated from a set range of values (depending upon your technique) on either a set given range of values or sampled from the image (my preferred way), with blending mode set as colour and the opacity set to suit.
that's exactly what i'm doing now, including sampling from the image. my question is, is there a way to not only sample the colour but it's brightness too and place the colour on the gradient map according to it's sampled brightness? right now, i sample the colours and kind of guess where to put them on the gradient map - with not very good results. how do you decide where to place them on the map??
thehermit wrote:
There are many ways to unify skin tones and blotchy skin and there are even more ways to unify slightly more saturated or uneven skin tones. I can think of more appropriate techniques but they may not be applicable to you, so I hesitate.
yes, my main goal is to unify skin tones when for example for a part of the image they have a greenish cast, or too pink highlights. sometimes i paint in with a solid colour set to colour blend mode, and it works but as soon as i stay in areas of the same brighness, in darker areas the colour becomes too saturated.
thehermit wrote:
If you have an example of the type of effect that you are attempting to create, by all means post it.
I'll try to find something but i didn't really have a specific image in mind, i just thought generally it might be an elegant way to control skin tones.
Joined: 05 Mar 2003
Posts: 3987
Location: Cheltenham, UK
Posted: Thu Jul 14, 2011 5:19 am Post subject:
Using a gradient map is normally reserved for local areas of tonality rather than across the whole of the image, saying that using a 'blend if' command does help to unify the results.
Gradient maps work on the luminosity values, you may be better advised to use curves adjustments and a whole lot of masking, as gradient maps don't work on hue values. Also areas of contrasting luminosity may not be best suited to a GM.
There is a method I use to unify patchy or blotchy skin tones, the inverse high pass technique. Rather than blather on, I will throw some links your way, which hopefully will provide more illuminating. Excuse the haphazard fashion they appear in, and apologies for making you do the sifting for useful information!
Using a gradient map is normally reserved for local areas of tonality
Exactly what i want to do. The problem lies in generating them.
Anyway, thanks for the links, good stuff!
As for my problem, i found a way - not as convenient as i hoped, but closer to what i wanted:
When you sample the colours, the colourpicker-dialog shows you the Lab-values. The L-value of that is a number between 0 and 100. Now if for example the colour has a L-value of 85, i place this colour on the 85%-position on the gradient map. Results are pretty close.
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