Adjusting the alpha value based on color

[baalazmon]

Hello, i've been working with PdN for a while, and now im mostly using it to combine/touch up renders, im going to get more into creating with it soon. So my question is; I have an image, and i want the black in the image to be more transparent, like around a sun, it would gradually fade from light>transparent, not suddenly shifting, I cant find this explained anywhere. If requested I will post the images, but they are quite large filesize, so it would take a good amount of time to upload.

Thank you for your time

-Baal

[Sarkut]

Radial gradient with black primary and transparent secondary.

If this is different from what you want then need more explanation.

[baalazmon]

I mean, would there be a way for it to make the black in an existing picture more transparent, so the darker the more see-through. So i could replace a pure black sky (with scenery and sun already) with a starfield or something else.

[Sarkut]

Thanks for clarifying.

You want to be using an Alpha Mask.

[Rick Brewster]

Please edit your thread title -- see [rule=6]rule #6[/rule] for the reason why.

[baalazmon]

thanks sarkut, and sorry about that, now its fixed

[Phyxius]

Use the advanced option of curves+.

Input - Luminosity

Output - Alpha.

Then leave the rest as it is, and hit OK.

for the area you highlighted (or the whole picture), luminosity (brightness) will now = alpha.

You can play around with it and fine tune it as well.

[baalazmon]

thats exactly what i needed, thank so much

[Phyxius]

No problem, I use it all the time. 8)