Vectorization (image tracing)

In computer graphics, vectorization refers to the process of converting raster graphics into vector graphics.

Popular applications

• 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.

Unlike the opposite process rasterization, vectorization is not well defined, meaning there is not a single correct method. Many different algorithms exist, and each gives different results, as vector representations are more abstract than pixels.

• 

  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

Vectorization algorithms

One algorithm of vectorizing edges is described in the open-source project Outliner. This algorithms uses the small vector-described rectangular shapes called the contour dots that hover above the pixels. The statistics of the underlying pixels is used for positionning and orienting the contour dot at the centerline of the edge. This algorithm can be used in the computer vision for the replacement of such classic edge detection methods as Roberts Cross, Canny and Sobel.

See also

• Scanning
• Digitizing
• CAD data exchange
• Comparison of raster to vector conversion software
• Optical character recognition

External links

• Online raster image vectorizer using the AutoTrace library.