Non-destructive color change

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Juan
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Non-destructive color change

Post by Juan »

Hi all,

I have been scratching my head whole day and I can´t find a proper solution for this, let me try to explain:

I have two layers, one is a picture of a metal roof and another layer is a white fill layer in Multiply mode (this last one is a requirement by the web master), this multiplied layer is meant to change the color of the base roof as the customer needs or by a color code, the problem is that I can´t find a way how to "color correct" the base roof in order that the multiply layer match as close as possible some color codes (reds, greens, light grey, etc).
I have right now 2 Curves layers and one Histogram correction trying to avoid the "darkening" of the roof without loosing details but honestly I feel like I reached a dead end now.

Here is a small screenshot, the dark grey roof is the one that needs to be "colored" by the white multiply layer to match the red one.
Roof.jpg
Here I made the white layer colored with the red color code in multiply mode and as you can see the roof become way to dark and there is not even close to the red roof that I need to match.
roof2.jpg

Can someone please throw me a light here?

Cheers
Juan
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Hoogo
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Re: Non-destructive color change

Post by Hoogo »

I'm not sure if a pure multiply thing can work perfectly enough. The glossy parts of the roof reflect the sky. Imagine a very flat look onto a glossy surface, you will only see the reflection, no matter what color the surface has.

I think I would add a layer above the multiply, containing some light sky, masked by the luminance of the original roof.

If the webmaster says that this is not possible, then I would place a curves between the roof and the multiplying layer and adjust the 3 rgb-curves to fit just this kind of red roof. But I guess the result would be stupid if you excghange the red multipling layer with another color.
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Wayland
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Re: Non-destructive color change

Post by Wayland »

Can you not change the multiply blend mode to colour and then just mask the non roof areas out?
Roof.jpg
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Hoogo
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Re: Non-destructive color change

Post by Hoogo »

I tried multiply, and it's a mess. The chosen red (192/64/64) is still too saturated.

I had another try with 255/128/128 and different curves. That looked better, but this color is much too different from the color of the desired roof and not useful as a color selector anymore.
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Juan
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Re: Non-destructive color change

Post by Juan »

Hoogo wrote:I'm not sure if a pure multiply thing can work perfectly enough. The glossy parts of the roof reflect the sky. Imagine a very flat look onto a glossy surface, you will only see the reflection, no matter what color the surface has.
I´m not sure about been the multiply the best choice since it darken the colors.
Hoogo wrote:I think I would add a layer above the multiply, containing some light sky, masked by the luminance of the original roof.
That´s a great idea, I´ll play with it. :)
Hoogo wrote:If the webmaster says that this is not possible, then I would place a curves between the roof and the multiplying layer and adjust the 3 rgb-curves to fit just this kind of red roof. But I guess the result would be stupid if you excghange the red multipling layer with another color.
I asked him if there are technical reasons for choosing multiply, (still waiting for his answer) because I got semi/ok result using Linear dodge, but again it looks ok for red but then if the layer is light grey it looks really really bad. :cry:
Wayland wrote:Can you not change the multiply blend mode to colour and then just mask the non roof areas out?
I hope so, like all of you noticed the multiply is not the best choise, but since he is programing the web thing not sure how that works behind the scene.
You got a nice result in your test. :)
Hoogo wrote:I tried multiply, and it's a mess. The chosen red (192/64/64) is still too saturated.

I had another try with 255/128/128 and different curves. That looked better, but this color is much too different from the color of the desired roof and not useful as a color selector anymore.
It´s really a difficult situation because we go from light grey to black passing through red and brown :? , the color choice is way to wide that I´m clueless about creating a "parametric" layer to get any color that the user wants to put. :(

Cheers
Juan
bkh
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Re: Non-destructive color change

Post by bkh »

In order to use "multiply", you'll have to convert the roof to b/w and adjust the histogram in such a way that the natural colour of the roof becomes white. (As Hoogo mentioned, you'll lose highlights on the roof in that way, but "multiply" can only darken colours.)
roof-no highlights.jpg
To fix this, you can restore the highlights by creating a mask for a white layer from the light parts of the roof and put that semi-transparent layer on top – it should not be a problem to superimpose a semi-transparent layer on top of the multiplied layers.
roof.jpg
I've attached a sample PLD file, the colour layer is in the group.

Cheers

Burkhard.

P.S. Apologies, I didn't spend much time creating the mask for the roof …
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Juan
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Re: Non-destructive color change

Post by Juan »

Wow Burkhard, that works great, thank you so much. :D
Tomorrow when I get to the office I´ll try it in the actual project and share the result.
bkh wrote:P.S. Apologies, I didn't spend much time creating the mask for the roof …
Don´t worry, the most important thing is the guidelines. :)

Cheers
Juan
Sus
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Re: Non-destructive color change

Post by Sus »

Another, easy (lazy) way using a free plugin (no layers, no masks) :)
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Juan
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Re: Non-destructive color change

Post by Juan »

Sus wrote:Another, easy (lazy) way using a free plugin (no layers, no masks
Thanks, that´s a great solution but sadly for a non destructive color modification it doesn´t work :(

Now, as promised here is the result using the guidelines shared by Burkhard (I owe you a beer or coffee :D ), I just adjust the highlights curve to have a little more smooth transition between dark and light areas.
I´m pretty happy with the result now, let´s see what the web master says.
Roofs2.jpg
Cheers
Juan
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