Detecting and measuring streams. (a) The input image: NGC 4981 in z band. The red aperture has a radius of 7 arcsec and lies on the thinnest and most diffuse end of the stream. (b) All pixels not belonging to the galaxy (detected by NoiseChisel) or its stream are masked, including the pixels of objects that are in the background or foreground of the stream (‘clumps’ in Segment). (c) All masked pixels interpolated by the median of ten neighbors. (d) The flux in the red aperture (dotted line), compared to a distribution of 10 000 similarly sized apertures, randomly placed over undetected pixels of the image (4.32σ). (e) The input dataset warped to a pixel grid where each pixel is 8 × 8 larger than the input’s pixels, to demonstrate the detection success on the input resolution.