Switch Gray to Alpha, but actually using gray (#808080) as the zero alpha versus white or black?

[Lxndwich]

So, I have these images I'd like to change to have a proper transparency, to where the areas lighter and darker than gray are preserved.

 

BoltBait's plugin, which I thought would work, only offers a change from white or black, which isn't ideal for the examples I have.

 

I have 5 images I'd like to change, and only one of them has an example that has the alpha already applied by the original image authors. I'm hoping that, by matching the transformation to the existing alpha image, I can change the other images without an alpha version to be as accurate as possible.

Below are the five images I'd like to change (Props to you if you recognize where these are from, heh.):

The fourth image has an existing version that is already transparent (This may not show up the best on the forums, since in the past, some images with transparency haven't rendered well.):

Any help on this matter would be greatly appreciated. Also, I've uploaded a separate copy of the version of the 4th image with alpha, just in case the version on Imgur has the alpha incorrect on their end and not on this end.

[frio]

From the existing image you uploaded, the buttons are more or less pure black or white with varying states of transparency, instead of shades of gray with varying transparency, so best I can think of is just an approximation but not exact. The "Make color transparent" adjustment from KrisVDM's pack seems to do a reasonable job (set target color to 128, 128, 128, set power to 1). However since the insides of the buttons are close to the background gray, it would pretty much require more manual work than just a simple effect to get the transparency and color levels to match.

 

Edited June 13, 2023 by frio

[Lxndwich]

2 hours ago, frio said:

From the existing image you uploaded, the buttons are more or less pure black or white with varying states of transparency, instead of shades of gray with varying transparency, so best I can think of is just an approximation but not exact. The "Make color transparent" adjustment from KrisVDM's pack seems to do a reasonable job (set target color to 128, 128, 128, set power to 1). However since the insides of the buttons are close to the background gray, it would pretty much require more manual work than just a simple effect to get the transparency and color levels to match.

 

Yep, that seemed to work. All I had to do to make it 100% accurate was select all the lighter tones and increase contrast by 25, then select all and decrease contrast by 50, then use the "Make color transparent" tool. Some end results (particularly 1, 4, and 5) are attached below.