Digital booths
Why a transparent portrait can show a dark fringe on a new background
The edge pixels may contain colour from the previous background.
A portrait cutout can look clean over white and develop a dark or coloured outline over another strip background. The alpha edge may contain premultiplied or contaminated colour from its original backdrop.
Inspect semi-transparent pixels
Soft hair edges contain partially transparent pixels that blend foreground and background values. If those pixels were created against a dark backdrop, placing them over a light canvas can reveal a dark fringe. The problem is different from a transparent canvas simply displaying as black.
Evidence: Web standard
Test against contrasting canvases
Preview the cutout over black, white and the intended strip colour. If the halo changes with the canvas, inspect the edge matte or extraction process. Keep the original portrait so you can regenerate the mask without compounding edits.
Choose a compatible export
Use a format that preserves alpha for the transparent master and check how the target editor composites it. If the destination cannot handle transparency reliably, export against the final chosen background. Do not repeatedly erase the fringe by trimming into hair detail.
Evidence: Web standard
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.