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Why flood fill beats a simple colour key
A plain colour key removes every pixel of a given colour, wherever it appears. If your logo contains the same colour as the background, it punches a hole right through the middle. Flood fill avoids that entirely: it starts at the image border and only spreads through connected pixels. An enclosed region inside the subject is never reached, so it survives untouched.
Getting the best result
- Check your background is reasonably uniform. A flat studio backdrop or a solid colour works. A busy photo of a desk will not.
- Keep the subject away from the frame edge. If your product touches the border, add a couple of pixels of margin first — flood fill will otherwise leak into it.
- Raise the tolerance gradually. Start around 15%. Stop the moment the background is clear; going further eats soft edges and hair.
- Download as PNG. Required for transparency.
Good candidates and bad candidates
| Image | Result |
|---|---|
| Logo on a flat colour | Excellent |
| Product on a paper sweep | Very good, after shadow correction |
| Screenshot of a UI on a solid colour | Excellent |
| Person against a plain studio wall | Good — watch hair edges |
| Pet on a carpet | Poor |
| Anything on a textured or busy background | Not suitable — you need AI segmentation |
If your subject has a coloured fringe after removal, the background and the subject were
blending at the edge. Feathering is automatic here, but softening the background first with
remove white background can give a cleaner boundary.
FAQ
How does this background eraser work?
It samples the pixels along the border of your image to learn the background colour, then spreads
outward from the edges, erasing every connected pixel close enough to that colour. Only connected
regions are removed, so a matching colour inside the subject is safe.
Does it work on a photo with a busy background?
No. Flood fill needs a reasonably uniform background. Busy scenes require AI subject segmentation,
which is a different kind of tool.
Why is part of my subject getting erased?
The tolerance is too high, or your subject touches the frame edge with a colour similar to the
background. Lower the tolerance, or crop the subject inward so it does not touch the border.
Is there a limit on image size?
Images up to 25 MB, processed at up to 3200px on the long side. Very large images take a few
seconds because the flood fill is computed per pixel.
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