[Noob] Blending

[JosephBw]

Running: GIMP 2.10.6

Upon watching a video on Youtube about creating a flare in GIMP, I came across a snag when using blending modes other than "Normal." The video explained that Screen blending changes opacity based on the brightness of pixels in a layer. However, in practice, this was not at all what happened.

Here's what I'm trying to do: get rid of the darkest pixels in a picture, leaving them transparent, while keeping the brightest ones.

When the Background layer's colour was black or white, every blending mode affected the image the same, changing the transparency of each pixel at the same rate regardless of its brightness. When the background layer was transparent, every blending mode other than "Normal" just made the image layer invisible regardless of the percentage I'd set the Opacity slider. Honestly, I don't really know what to do here. I'm kinda getting worked up about the whole thing. I know I'm a noob, I've looked everywhere, and even though it seems straightforward I can't seem to get the thing to work.

[rich2005]

I had a quick look at youtube +gimp +flare and there are too many, some manage to drag out to 20 minutes.

Back to basics. You might be able to do something like this, depends on your flare.
Have you tried removing the background colour using Colours -> Colour to Alpha ?

As an example using the standard Gimp 2.10.6 lensflare Filters -> Light & Shadow -> Lens Flare on a black background.
and maybe change the colours using Hue Saturation A couple of screenshots: https://i.imgur.com/tvlQoWt.jpg

Now using Colour to Alpha changing the default white to black. There are two sliders, Transparency Threshold and Opacity Threshold. Adjust to suit and ok. Another couple of screenshots. https://i.imgur.com/5GhqLDh.jpg

You do not get this in any of the old tutorials, colour-to-alpha in Gimp 2.8 was all or nothing.

[JosephBw]

(09-09-2018, 05:45 PM)rich2005 Wrote: I had a quick look at youtube +gimp +flare and there are too many, some manage to drag out to 20 minutes.

Back to basics. You might be able to do something like this, depends on your flare.
Have you tried removing the background colour using Colours -> Colour to Alpha ?

As an example using the standard Gimp 2.10.6  lensflare Filters -> Light & Shadow -> Lens Flare on a black background.
and maybe change the colours using Hue Saturation A couple of screenshots: https://i.imgur.com/tvlQoWt.jpg

Now using Colour to Alpha changing the default white to black. There are two sliders, Transparency Threshold and Opacity Threshold. Adjust to suit and ok. Another couple of screenshots. https://i.imgur.com/5GhqLDh.jpg

You do not get this in any of the old tutorials, colour-to-alpha in Gimp 2.8 was all or nothing

Thanks a metric ton, this helped a lot. Have a great day.