Add an alpha channel first
A single background layer in GIMP has no transparency, so deleting pixels fills them with the background colour. Layer → Transparency → Add Alpha Channel gives the layer somewhere to store transparency [1].
Foreground Select: research inside GIMP
Foreground Select is based on SIOX (Simple Interactive Object Extraction) from Freie Universität Berlin and first appeared in GIMP 2.3.3 [2]. In GIMP 2.10 its default engine is “Matting Levin” [3] — named after Levin, Lischinski and Weiss's closed-form matting method, which estimates soft transparency at edges [4].
Color to Alpha for flat graphics
Colors → Color to Alpha makes a chosen colour transparent, turning partly-matching pixels partly transparent [5] — ideal for logos and line art on white, wrong for photos where the same colour appears inside the subject.
GIMP 3
GIMP 3.0, released in March 2025 after 2.10 in 2018, keeps the same tools and menu paths [6].







































