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How to make a single color image with white alpha layers into white transparent png


blasteralfred

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Hi,
I have an image. The image has a solid background and the drawing in it is made by various white and black layers, with transparency settings, one over another, to make a complex image. The image sample is below;

thumb.jpg

What I want is to change the colors. This can be easily done with hue/saturation settings. But i an looking for something different :cool2:. I want the drawing to be gray and white, so that when I place the layer(s) over a blue background, it will look like this.

How can I do this? Somebody help me pls..
Thanks in advance...
 

Tom Mann

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Re: How to make a single color image with white alpha layers into white transparent p

When you say, " I want the drawing to be gray and white, so that when I place the layer(s) over a blue background, it will look like this...", are you talking about layering them inside of Photoshop, or in the real world, e.g., with sheets of transparent plastic like old Vugraph transparencies?
 

blasteralfred

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Re: How to make a single color image with white alpha layers into white transparent p

Inside photoshop. Also I can do the same inside web page.
 

Tom Mann

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Re: How to make a single color image with white alpha layers into white transparent p

I think there may be a bit of a difference in terminology, especially in the way you titled this thread, which of the images are png's, etc..

Ignoring the title and going by your written description, I think that what you are asking is to be able to place a B&W version of your image (ie, like this)...

thumb-tjm01_acr-ps01a-01_converted_to_BW.jpg

in a layer stack above a solid color layer (ie, like this)...
screen_grab-layer_stack2.jpg

to come up with a result like this ...
thumb-tjm01_acr-ps01a-02_BW_placed_above_orange_solid_layer.jpg


or this.
thumb-tjm01_acr-ps01a-02_BW_placed_above_a_green_solid_layer.jpg

If that's what you are asking, just change the blend mode of the B&W layer to luminosity (in the above layer stack), and you are done. If not, please let us know.

Tom
 
Last edited:

blasteralfred

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Re: How to make a single color image with white alpha layers into white transparent p

Dear Tom,
you are almost there, but not exactly.
I want the image to be semi transparent, so that it can be placed over any color. If I can export the image, without background color, as PNG with alpha channel, I can place the image, say, in a web page, over a solid color, so that the image will look like the original one.
I want just the b/w fish only, without any bg color, having alpha channel. Then I can place the fish over any solid color layer, so that the fish look exactly same.
In short, the fish should not have any bg color, and the fish must be made up of b/w colors. The brighter portions may have, say opacity 100% and the semi white (colored) portions may have a different opacity. Then, if I place the fish over a "same" blue solid background layer, the fish may look exactly same. ;)
 

blasteralfred

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Re: How to make a single color image with white alpha layers into white transparent p

Hi,
Yes, I am looking for something like this. :)
But, did you tried with the same blue color? I want this, if you place the fish over a same blue colored layer, the fish should look exactly the same (it should have same colors). And if I place the fish over a red background, the fish may change colors accordingly, like we set using hue/saturation settings. Thats what I am looking for. A semi transparent fish layer, having just b/w colors.
 

Tom Mann

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Re: How to make a single color image with white alpha layers into white transparent p

Ahh, now I understand what you are getting at. I don't think you'll be able to achieve exactly what you want. I think that the best you can do with a single layer (plus its alpha channel) is something like this:

Have the alpha channel carry the saturation information so that higher saturation maps into more transparency of the layer so that more of the (presumably fully saturated) underlying solid color layer shows through. In regions of low saturation, only the B&W (ie, unsaturated) image layer is visible.

The luminosity info would then have to be carried on the B&W layer itself. It's easy to see the problem that this causes. Suppose you want to produce a bright or a dark region with maximum saturation. In this region of the image, the alpha channel would be telling the B&W layer go transparent so as to achieve maximum saturation. However this means that in this region, the luminosity of the B&W layer would be ignored. The luminosity of the result would then be nothing different than the luminosity of the solid color layer. Put differently, you would lose luminosity info in regions of maximum saturation.

OK, so this approach obviously isn't going to work. What are our other alternatives?

One alternative might be to not have the alpha channel ever go to fully transparent. This would allow some luminosity info to get through (the problem with the previous approach), but it introduces lots of other problems. For example, it would prevent fully saturated colors from being displayed.

Another possibility is to think about having the alpha channel carry the luminosity info and the layer itself carry the saturation info. Well, I think it's immediately obvious that isn't going to work, either.

Another alternative might be to use multiple layers, each with it's own alpha channel, say, an all white layer, an all black layer, and one or more solid color layers, all with the same hue. I think one would be able to get a much better approximation of the brightness and saturation variations in the original image with a system like that, but that doesn't give you what you asked for: exactly one layer with one alpha channel.

This is why in mathematics, many proofs begin by first demonstrating an existence theorem. In this case, you obviously don't have this because you are effectively asking us to provide you with an "existence theorem", ie, provide you with just one example where what you asked for can be demonstrated to be possible.

HTH,

Tom

PS - The reason that my previous post described a method that didn't use an alpha channel was that I was pretty certain you couldn't get exactly what you asked for, so I described an approximate one layer method that at least wouldn't look too bad: The hue and luminosity information in the result would perfectly match the original, but the saturation would be constant throughout the image. As mentioned above, if you allow more layers, even that limitation could be removed.
 

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