Drop an image onto the window, or click the frame in the center of the screen to choose one. The lines appear right away. Pick a group in the Settings panel and its values appear in the child panel beside it.
Silhouette splits light from dark at the threshold and takes the border between; edge takes the change in brightness itself. Blur, simplify, and noise removal clear away the stray lines. The wheel zooms, and holding space while dragging moves the image. Save as an SVG or a PNG at its original size from the Main panel.