Glow / Bloom
Bloom is what happens when bright light scatters inside a lens or an eye: a highlight bleeds softly into everything around it. The implementation matches that — pull out the pixels above a brightness threshold, blur them heavily, then screen the blurred copy back over the original. Only the bright parts glow, which is what stops it looking like a plain soft-focus blur.
Drop images here
PNG, JPG, WebP — multiple files allowed
Threshold first, then radius
The threshold decides what glows, and it is the control that determines whether the result looks deliberate. High — 75 to 90 — and only genuine highlights bloom: a lamp, a sky through a window, a specular reflection. That is the photographic use. Low — 30 to 50 — and most of the midtones contribute, which washes the whole image in light; that is the dreamy or ethereal look, and it is also how you accidentally ruin a photograph. If the picture has no bright areas at all, nothing will happen at any threshold.
Radius sets how far the light spreads, in pixels, so it needs scaling with the image. Something like 2% of the long edge is a natural-looking spread; 10% is a heavy cinematic bloom. Large radii cost real time because they are three box-blur passes over the whole image per channel, and a 200-pixel radius on a large photo will take a moment.
Screen against add, and the tint
Screen is the safe blend: mathematically it can approach white but never exceed it, so highlights stay smooth and nothing posterises. Add simply sums the values and clips at 255, which blows bright areas out to flat white with a hard boundary. That harshness is sometimes what you want — neon signs, sci-fi UI, anything meant to look like it is emitting rather than reflecting — but screen is the better default.
Leaving the tint on "match the highlight colour" means a red lamp glows red and a blue screen glows blue, which is what a real lens does. Forcing a tint replaces that with a single colour and is a straightforward colour-grading move: a warm bloom reads as sunlight or tungsten, a cool one as moonlight or a monitor. It is a much stronger effect than it sounds, so start at a lower intensity when using one.
FAQ
Nothing happened.
No pixel exceeded the threshold. Check the image actually has highlights — Histogram will show you — and lower the threshold. An evenly mid-lit photograph has nothing to bloom.
How is this different from Blur?
Blur softens everything equally. This blurs only a brightness-selected copy and adds it back, so the underlying image stays sharp and only the light spreads. A glow over sharp detail is the effect; a blur over everything is just an out-of-focus picture.
Can I glow the whole image regardless of brightness?
Set the threshold to 0. Every pixel then contributes, which gives a uniform soft-light haze — the Orton effect. Keep the intensity low or you lose all contrast.
Does it work on transparent PNGs?
The alpha channel is untouched, so the glow stays inside the existing shape rather than spreading beyond it. To make light spill outside the object, add transparent padding first with Add padding, then flatten, then glow.