Image tracing

In computer graphics, image tracing or vectorization is the conversion of raster graphics into vector graphics.

Examples[edit]

In computer-aided design (CAD) drawings (blueprints etc.) are scanned, vectorized and written as CAD files in a process called paper-to-CAD conversion or drawing conversion.
In geographic information systems (GIS) satellite or aerial images are vectorized to create maps.
In graphic design and photography, graphics can be vectorized for easier usage and resizing.
Vectorization is often the first step in OCR solutions for handwritten text or signatures.

Signature of Christopher Columbus as JPEG image (1,308 × 481 pixel), 63 kB
Vectorized two-color variant of the signature of Christopher Columbus, 19 kB

Unlike the opposite process, rasterization, vectorization is not well defined, meaning there is no single "correct" method. Many different algorithms exist, and each gives different results, as vector representations are more abstract than pixels. The following tracing examples of a hard to vectorize photo illustrate these limits.

A photograph in JPEG format, 25 KB
The photograph at left vectorized with RaveGrid, 1.64 MB
Same photograph vectorized with AutoTrace in the Delineate GUI, 677 KB
Same photograph vectorized with Inkscape's "Trace Bitmap" function, based on potrace, 1.05 MB
Same photograph vectorized with Scan2CAD, 340 KB
Vectormagic, 12 colors, 369 KB
Vectormagic, all colors, 744 KB