Problem separating color from picture

[_jason_]

This is somewhat of a technical nature...

Maybe I am too stupid or do not see the possibilities, but I have some problems simply dividing a color picture into its 2 composite parts:

1. The complete color information (that is without the greytones).
2. The complete monochrome/greyscale (contrast) information.

What I want to achieve is that these two images put together with overlaying result in the original surce (color) picture again finally.

The reason why I want to do that is, I want to modify only the color separation in a special way prior mixing all together again. (This actually could give a wide range of creativity for special modifications and some artistic expression.)

Has anyone a solution for this problem or an idea how to get these two composite image parts from any photograph?

(Well, I actually could write a programm which extracts that information from the pixel data but I want to do that with Photoshop on the fly.)

Thanks.

[Flashtones]

Have you looked into lab mode?

Otherwise, in RGB, dupe your composite layer and set one to Luminosity and the other to Color.

[_jason_]

No I didn't look into the lab mode. Is that possible there?
RGB mode does not work the way I need it. None of the layer mode gives me a true color separation.

[_jason_]

With Programming you simply would do the following:

You analyze the RGB values for the lowest grey tone. I.e. The pixel value is R:170 G:54 B:69. Then the lowest greytone is logically R:54 G:54 B:54. That's the contrast or monochrome part then for the given pixel.

Then the resulting rest is the color tone, which has to be separated: R:116 G:0 B:15.
(You simply subtract the lowest grey tone from the source pixel.)

Doing that over the complete image data actually would result in one picture with the greyscale and onoter with the color tones.

Mixing it together would result in exactly the same image than the source picture.

I think this isn't possible to achieve with overlay modes. Did not find a tool also. (I tried "Selective Color" already but did not get really usefull results.)

Is there something to calculate such images in PS?

[ApWizard]

When I need that I go for this way: create a blank layer over the one you want to separate colors from. Fill this layer with white, change the blending mode to color (is not the same of desaturating). Press CTRL+ALT+SHIFT+E to merge all in a new layer, delete the white one. Change the blending mode of the new grayscale layer to Linear Light and invert it.
At this point I don't remember (I've to try it) if it is done or if I've to change the opacity of the Linear Light one to 50%.
CTRL+ALT+SHIFT+E for the second time and delete the Linear Light layer.

So, here you have your colors information.
For reapplying the colors just put this layer in Linear Light (maybe with the 50% opacity).

[ApWizard]

Originally Posted by _jason_

With Programming you simply would do the following:

You analyze the RGB values for the lowest grey tone. I.e. The pixel value is R:170 G:54 B:69. Then the lowest greytone is logically R:54 G:54 B:54. That's the contrast or monochrome part then for the given pixel.

Then the resulting rest is the color tone, which has to be separated: R:116 G:0 B:15.
(You simply subtract the lowest grey tone from the source pixel.)

Doing that over the complete image data acually would result in one picture with the greyscale and onoter with the color tones.

Mixing it together would result in exactly the same image than the source picture.

I think this isn't possible to achieve with overlay modes. Did not find a tool also. (I tried "Selective Color" already but did not get any usefull results.)

Is there somethingl to calculate such images?

You can do that in Linear Light (as I described before) or by Apply Image...

With programming there's not only the way you described to calculate the monochromatic...there are many but they all works

[_jason_]

Thank you!

But I already did something very similar. The problem with that is, mixing it together does result in a slightly different image. The contrast information anyhow is modified. It is not exact enought.

[ApWizard]

Originally Posted by _jason_

Thank you!

But I already did something very similar. The problem with that is, mixing it together does result in a slightly different image. The contrast information anyhow is modified. It is not exact enought.

No way!
If you do it correct there's no variation at all.
I will try with PS opened and post the right procedure asap

[_jason_]

So, here you have your colors information...
For reapplying the colors just put this layer in Linear Light (maybe with the 50% opacity).

Apply on the greyscale image, right?
If I do that, I get something in middle grey mixed with the colors !?

Oh that would be nice to have! Thank you!
I was nearly at the point where I strated Microsoft Visual C++ to code the tool myself...

Jason

[_jason_]

I think one of my problems was, that I generated my monochrome image with desaturation. Doing such gives obviously slightly more contrast ...

[ApWizard]

Well the Linear Light method produce some incongruence while recomposing so we have to work in 16bit mode with Apply Image:

• create a new layer, fill with white, change blending mode to color;
• merge all in a new layer, duplicate this and delete the white one;
• Apply Image on the second duplicate:
- layer: the color image one;
- invert: checked;
- blending: Add;
- scale: 2;
- offset: 0;

• invert the layer (CTRL+i);
• change the blend mode to linear light;

the Linear Light-colors-only layer stay over the black and white one.

Attachments:
1) color image;
2a) black and white layers done with a white layer in color mode (color contrast is visible)
2b) black and white using desaturation (no color contrast), that's the wrong way;
3) second copy of b/w layer after Apply Image and inversion;

actually there is no difference between the original image and the recomposed one. Just merge all and put in Difference blending mode over the original one, the result is a pure black (0000000) stating there is no difference at all

[_jason_]

I think, I did it exactly as you described first and it basicly worked. But if I mix the images together there is a slightly shifted contrast to the original...

Oh wait, you posted just a new message. I will try that now...

Good hint with the 16 bit mode! I am relatively new to Photoshop, so I have to learn alot...

[Der_W]

I always used to create a duplicate of the background layer, set its mode to "Color" and fill the background layer with a 50% gray (or any shade of gray, that's just my standard fill entry ;-)).
After that go to "Edit"-"Fade" and fade it to "Hue" mode.
Works great for me (and using yet another copy of the background layer on top in "Difference" mode tells me that there's no difference between the original and the color separated image.

I uploaded you an action that does exactly that if you didn't understand everything I explained :-)

[_jason_]

That's actually a drastically simplified version of the first one and it does not produce any difference in contrast like the stuff above (without "Apply Image").
Much faster too.

Really great!!!

But the problem with all those techniques is that the color is placed on that grey background. I think it's actually limiting creativity.

[_jason_]

Is there a way to generate alphatransparent images from the gray color pichture?

[ApWizard]

Originally Posted by _jason_

That's actually a drastically simplified version of the first one and it does not produce any difference in contrast like the stuff above (without "Apply Image").
Much faster too.

Really great!!!

But the problem with all those techniques is that the color is placed on that grey background. I think it's actually limiting creativity.

I think that is mathematically correct. If you have some white in the image, or black or gray, there is basically no color information and that's expressed by 50% gray.
Linear Light in the recomposition (or the others blending modes used by Der_W in the simplified working version) ignore that 50% gray.
As far as you don't touch the luminosity it works fine.

[_jason_]

I think I'll take a look at the plugin SDK.
I need the separation in another way as it is done with the techniques above.

I really need accurate separations of the greyscale and the color channels as alphatransparent images. Also (optionally) red, green, blue separations on alphatransparency.

The parts have to give 100 percent accurate result if merged back on a white background (no blending modes used at all then).

I know there is a plugin called "Tinter" or so, which does just similar things (recoloring images by separating color information and re-applying modifications to the generated greyscale images). Surely worth to take a look at that too...

Thanks for all the help!

Jason