Inspiring

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Photoshop needs "Color to Alpha" button

Forum|Forum|5 years ago
October 15, 2020
13 replies
9541 views

I was just chatting with a group of other artists about the need to convert a color into transparency sometimes, and we've all needed such a function, then somebody said that in GIMP there's just a simple button for it, "Color to Alpha." It does exactly what we need and very easily. In Photshop this is possible but very cumbersome, having to use the channels to make a selection, then apply a mask.

Googling leads to 10 year old articles and people recommending plugins. But yeah, I'd just like to suggest this as an official feature request.

You know how in Photoshop you can use Replace Color? And you can pick a color, and vary the fuzziness of the selection, then change the color to something else? It would be just like that I imagine, but instead of changing the color, you increase the opacity of those pixels.

Feature request

Stephen Marsh

Community Expert

@unique_person4993 - There's also Krita which isn't a web app.

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unique_person4993

Known Participant

@M-H No problem! I'm glad my example was helpful, especially since the discussion earlier in the thread was talking about a picture on a white background, which there's technically a workaround for.

It's definitely a bit of a niche use case! I don't need it often but there's been a few times it would have been super helpful, and it just feels like something Photoshop should be able to do, since it's a feature that is possible in other programs? And is pretty similar to some existing functions Photoshop can do.

I'm not very savvy on the technical side of things, but it seems like there's a discussion here about how GIMP's Color to Alpha feature calculates things, though a lot of the conversation is rather old, with the thread being from 13 years ago... (Though this thread also let me know that a certain online photo editor has the feature as well! That may be my fallback for this in the future since GIMP and I seem to not get along very well.)

https://stackoverflow.com/questions/9280902/what-algorithm-is-behind-the-gimps-color-to-alpha-feature

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M-H

Inspiring

@unique_person4993 thanks for torough explanation, I get it now! Personally, I dont think I've ever actually needed that function for my work but now for sure I wouldnt mind that in PS! Any ideas on rgb math behind that function in GIMP? Frankly im struggling now to get even similar results in PS🤦‍♂I was hoping mix of masking and blend if would get at least in ballpark but its not the case...

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unique_person4993

Known Participant

@M-H Yes, two different actions in two different software DO produce completely different results, because they are two different functions that are not directly comparable. Hence why we're requesting that Photoshop add that function.

Here's an example of the "Color Range" and making the selection be the alpha channel in Photoshop, vs how it looks when using the "Color to Alpha" feature in GIMP. The black text was on a nice lavender background as shown by the dot next to it, and the red text was on a horrendous neon green background.

You can see that in the GIMP Color to Alpha example the lavender and green were completely masked out, with those pixels inbetween the colours becoming instead a semi-trasparent pixel that doesn't have any of the masked out colour in it.

(Yes I'm a real graphic designer, I made the font be Comic Sans to be a little silly with it all.)

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M-H

Inspiring

Of course results from 2 different pieces of software using different algorythms and with different user settings (100 threshold vs 200 fuzziness) are going to be different. Im pretty sure just gimp only could give 100s of slightly different results, what is your point? Author in the org post says she needs just a single button for it because in "Photshop this is possible but very cumbersome, having to use the channels to make a selection, then apply a mask." which isnt true

Stephen Marsh

Community Expert

Photoshop already has "selection to alpha" button and it also has Color Range selection so basically 2 step solution to get any colour transparent/masked. If thats too much clicking you can record both as action and turn dialog on for the first step:

Takes seconds to do either way so I wouldnt be expecting Adobe developers to be jumping on it to "reinvent the wheel"

By @M-H

If you read the first half of the topic, you will see that what the Color to Alpha function does in Gimp and Krita isn't the same.

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M-H

Inspiring

Photoshop already has "selection to alpha" button and it also has Color Range selection so basically 2 step solution to get any colour transparent/masked. If thats too much clicking you can record both as action and turn dialog on for the first step:

Takes seconds to do either way so I wouldnt be expecting Adobe developers to be jumping on it to "reinvent the wheel"

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unique_person4993

Known Participant

It looks like someone had previously told the original author to make another post as a feedback post, which I why I thought it was weird that it was merged into this one, BUT looking at the URL it's now in ideas rather than discussion, and it no longer has "solved" in the title, so I think they just thought this post was more informative and made it the main post. Probably a good idea! (It did lose a couple of upvotes though, one of the author's replies on the previous page has the content from the other thread with 12 upvotes, so I think that's where those went.)

@Stephen Marsh The action you gave me worked great! ...Except, this logo appearently uses a very dark gray rather than black, so it ended up making the letters semi-transparent. Which is how it's intended to work, but not exactly what I needed in this case. GIMP has an "Opacity Threshold" that can be used to keep colours that only have a bit of the colour you're removing from becoming semi-transparent with some tweaking, thankfully, which is a nice option.

I think this is another point towards why Photoshop should impliment this feature! (Especially because GIMP tried to export my image as a half a gigabyte file...?? No idea why. Not super fond of that program to be honest.)

dolldivineAuthor

Inspiring

A feature request for Photoshop to catch up with the rest of the world and add a "color to alpha" toggle like GIMP and Krita have.

A menu would pop up where you can select a hex code (similar to Replace a Color). Wherever this color is found would become transparent, and where it's partially found, it would become partially transparent. Maybe a fuzziness toggle.

See extensive discussion about this here:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/photoshop-needs-quot-color-to-alpha-quot-button/m-p/14569277

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Tim Wilkinson Lewis

Participant

I have been looking for this function in Photoshop for about ten years and it seems to be pretty much impossible to do it perfectly. The other downside is that most discussions online do not understand the required function. Why does this function not already exist, and if it doesn what it is called, I aM gOiNg MaDdd

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Anonymous

F Sose: your reply is wrong. Select , Color range does it NOT. Check e.g. GIMPs Color to alpha... set black, and it is perfect. I CAN NOT THIS REPLICAtE in photoshop. It is IMPOSSIBLE via any feature. Why is photoshop OVERLIMITED? You are NOT expert, you answer is USELESS. And LIE.

Stephen Marsh

Community Expert

@28298186

With hindsight, now that we have examples from Krita and GIMP that were not available when @D Fosse originally posted, I agree that the method outlined by D Fosse doesn't result in the same effect. I will unmark that as a correct answer.

The result of the action posted by @Jeff Arola is very similar to both Krita and GIMP, so I do believe that that is a correct answer. As the original action contained Japanese language-specific steps and failed on English versions, I have made an English version of the script.

The method shown by @c.pfaffenbichler should also be considered a correct answer.

This topic is a "discussion" and not an "idea" (feature request). @Alexander32558309721z if you make a new post labelled as an "idea" then I'll vote on it (You could just copy/paste most of your reply from here).

@28298186 I am not a moderator, however, I don't believe that your response meets community guidelines of being "kind and respectful".

D Fosse

Community Expert

@Stephen Marsh

Actually I just misunderstood the original request. Or some of the subsequent posters misunderstood, I don't know.

The fact is that there is a "color to alpha" action that has been floating around for years and years. I picked it up in 2014 and still have that thread bookmarked. These are the steps:

Open the doc (RGB mode only)
Make a new layer, fill it with full red. Invert it (Cmd-i).It'll go cyan.
Make a layer, fill it with green. Invert it, so it goes magenta.
Make another layer, fill with blue, invert to make yellow.
Turn off the new layers so you can only see your original.
Go to the channels palette.
Create three new blank channels. They'll be black.
Command-click the Red channel. This will make a selection. Change to your first new channel, and fill that selection with white.
Do the same thing for the green channel, into your second new custom channel.
Do the same for the blue channel, into the third custom one.
Control click your first custom channel (with the selection from the red layer). Invert the selection (command-shift-i). Go to your new red layer (which is now cyan), and apply the selection as a mask (by clicking the mask button).
Do again using custom channel 2, onto the new Green (changed to Magenta) layer.
And again, from channel 3, into the Blue (now Yellow) layer.
Set all 3 of your layers to blend type "Multiply"
Turn off any other layers.

I've kept and used this action occasionally over the years, and it works pretty well.

The only thing that offended me with G2829's post was that he got my name as "F Sose". Huh, you're talking to me? 😉 😄

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