Background Remover

A Colour Key, Not a Subject Detector

This page answers exactly one question, pixel by pixel: how far is this colour from the colour you chose? Pixels close to it become transparent, pixels far from it stay. There is no model of what a person or a product looks like anywhere in the code. Earlier copy here described automatic subject detection, edge-detection algorithms and brush tools; none of those ever existed, and the descriptions are gone.

Choosing the colour to remove

Click the background directly on the canvas and the colour beneath your cursor is read from the full-resolution file. Three shortcuts cover the usual cases — white for products on a sweep, black for dark studio work, and the standard green screen — and the hex field accepts a typed value when you already know it.

Sample a representative spot rather than the brightest one. A white backdrop is never a single white; it carries a gradient from the lighting. Taking a mid-tone from the middle of that gradient leaves the tolerance control far less work to do than taking the hottest corner.

Tolerance and edge softness

Tolerance is the radius, in colour distance, around your chosen value. Raise it and more of the backdrop vanishes. Raise it too far and it begins eating the subject, usually starting with whichever part of the subject shares a hue with the background.

Edge softness widens a band around that threshold where pixels fade out gradually instead of flipping from opaque to invisible in one step. At zero you get a hard, aliased cut. Around 30 percent produces an edge that will sit convincingly on a new background. Both controls are expressed in colour distance rather than screen pixels, which is why the preview and the exported file make identical decisions.

Check the mask before you commit

The magenta mask option paints everything that is about to be removed instead of removing it. It is the fastest way to catch the classic failures: a shirt cuff the same shade as the wall, a shadow the key has decided to keep, a fringe of backdrop colour still clinging to hair.

Where this approach breaks down

It cannot separate a subject from a cluttered room, a street or a lawn. It struggles with heavy shadows falling on the backdrop, because a shadowed white wall is grey, and grey sits a long way from white in the distance being measured. Semi-transparent things — glass, smoke, flyaway hair — come out partly keyed, since each of those pixels is genuinely a blend of subject and background.

If you control the shoot

Light the backdrop separately from the subject so it stays even across the frame. Move the subject a metre or two forward so their shadow does not land on the backdrop and so backdrop colour does not spill onto their edges. Do not dress the subject in the key colour, which is the reason blue screens exist alongside green ones.

The output has to keep an alpha channel

Transparency requires PNG or WebP. JPEG and BMP have no alpha at all, so those choices are upgraded to PNG for you rather than quietly filling the cut-out with a solid colour.

If a desktop viewer shows your transparent region as black or as a checkerboard, that is the viewer's rendering rather than a fault in the file — open it in a browser to confirm the alpha survived. When you want the subject placed on a flat colour instead of on nothing, Convert Image will composite it onto a background of your choosing during the format change.