Practical guide
Vectorize an icon set with transparent backgrounds
Crop the source sheet, remove only border-connected backgrounds, then choose a recipe for outline or shaded artwork.
Problem
Icon sheets often mix a near-white cell background with anti-aliased edges, narrow gaps, and attached neutral shadows. A broad color-key can erase white artwork inside the icon. Kurviq instead removes border-connected pixels and protects areas that are only reachable through narrow channels.
Command
npx kurviq --input icon.png --output icon.svg \
--remove-background auto --background-fuzz 3 \
--background-channel 3 --mode spline \
--filter_speckle 4 --path_precision 1 --segment_length 8Before and after
PNG SVG Accessibility, outline icon
Thin strokes and enclosed shapes after background removal.
The SVG keeps the enclosed outline while the removed background becomes transparent. Always inspect the result on a dark surface; white halos and accidentally removed light details are much easier to see there.
Workflow
1. Crop first
Export one icon per raster file with a small border around the artwork. Auto background selection reads the border, so a clean crop gives it an unambiguous sample.
2. Apply the shared spline recipe
Spline mode fits smooth contours. A speckle filter of 4 removes tiny islands, path precision 1 retains useful coordinate detail, and segment length 8 avoids over-segmenting rounded shapes.
3. Branch by style
For blurry flat or outline icons, add --upscale 2 --sharpen. For soft-shaded 3D icons, add --upscale 2 --gradient_step 8 --color_precision 8 instead. Sharpening flattens ramps, so do not combine it with the gradient recipe.
Flag reference
| Flag | Value | Why it is here |
|---|---|---|
--remove-background | auto | Samples the border and removes only connected background pixels. |
--background-fuzz | 3 | Uses a conservative color tolerance for near-uniform cells. |
--background-channel | 3 | Protects regions that can only be reached through narrow gaps. |
--mode | spline | Fits smooth curves instead of polygon facets. |
--filter_speckle | 4 | Drops isolated four-pixel noise. |
--path_precision | 1 | Keeps coordinates precise enough for small icons. |
--segment_length | 8 | Produces longer, smoother contour segments. |