Color to Alpha/Transparent?

[WonderKid]

In GIMP there is an option to remove a certain color from a layer and turn it transparent.


For example, if I had a completely red image it would remove all the red and anything that used to be red would be transparent. If I removed red from a purple image, that image would now be a slightly transparent blue.

I find it useful to make overlays and layer effects and also to do an "easy render" on some images.
I can't seem to find anything like that in PS6 though :<

Sorry if this is a weird question...

 

[ibclare]

Not a weird question, but one for Hawkeye or Stric9 or Tom Mann. Maybe others have played with this but I don't. Sorry I can't help. I'll play around with it in PS and see if I can come up with something.

 

[Samohtvii]

You could try the magic wand tool and and turn contiguous off and play around with the tolerance til you get what you want.

 

[Tom Mann]

There are lots of ways to generate an alpha channel / mask based on color in PS. Here are a few:

1. Use the "Color Range" tool. (Attachment #1)

2. Use the HSB/HSL plugin to map the hue distribution in the image to tonal values. In the example shown, green will be a mid-gray. Then use a curves layer (as shown) to turn hues around that value to white and darken all other hues. (Attachments #2 and 3)

3. My favorite is a plugin called "Asiva Select". From the screen grab, it should be self-explanatory how it works. (Attachment #4)

4. Don't neglect what appear to be spatial-based selection tools like the Quick Select tool. That one, in particular uses abrupt changes in hue to determine edges and isolate colored areas in the image. (Attachment #5)

There are other closely related tools (eg, the new adjustment brush in ACR in CS6, NIK Viveza, etc.), but the ones listed above are the 1st that came to mind given the way you phrased your question.

Obviously, once you have an alpha / mask, you can change almost any aspect of that area (eg, transparency, brightness, saturation, sharpening, etc.).

HTH,

Tom M

 

[MikeMc]

Still hearing Eagles Tom...

 

[ibclare]

LOL and XD Mike. Thanks Tom, I knew you'd "come through." Excellent. Thank you. I can use that information I'm sure.

 

[WonderKid]

Thanks

Not a one click option but it's nice to have at least ;D

 

[Tom Mann]

There are "one click" ways to generate an alpha mask that peaks at certain hue values, but I don't find them useful because they aren't very selective, so I didn't mention them. For example, simply duplicate the green channel and use the result as an alpha mask.

Another approach is to add a B&W photo adjustment layer on top of your image. Set the sliders to peak at whatever hue you want to emphasize, and the result is a B&W image that is brightest for objects with the desired hue, ie, again, immediately useful as an alpha / mask.

Unfortunately, neither of these approaches are terribly selective. If you want more selectivity, you have to do a tiny bit more work.

T

 

[Tom Mann]

PS - @ Mike Mc - LOL!

T