Vector graphics is a computer graphics concept that that defines an image as a set of points that are connected by lines and curves. This is in comparison to raster graphics which individually saves the value of each pixel.
This design concept means that vector images can be scaled up and down at will with no loss of quality or increase in file size. In comparison scaling raster images up increases the file size and results in pixelation as the computer has to guess what value the new pixels should be.
Issues with vector graphics
As much as it may sound like vector-based images should be preferred over raster-based images, this isn’t always the case. Vector images often struggle with complex scenes such as photographs. The smooth continuous changes of colour are essentially impossible to replicate in a shape-based format without massively increasing the file size in comparison to a raster image. For example, converting a raster format photo into a vector-based image can result in file size increases of between ten and a hundred times, while also coming with a very noticeable reduction in quality due to banding artifacts.
Tip: A banding artifact is an imperfection in an image where what should be a smooth transition of colours is instead obviously stepped, causing distinct bands of colour to be visible.
Where are vector graphics useful?
Vector graphics are generally useful for more simplistic images such as logos, where there are fewer complex shapes and finely detailed colouring. In these contexts, vector graphics can be scaled up and down at will with no degradation in quality. For example, you can zoom in as much as you want on a curve and it will still be smooth and sharp rather than becoming obviously jagged or blurry.
While the vectorisation, or process of converting raster graphics to a vector format, comes with many issues, the reverse isn’t true. The rasterization of vector images is simple to do as the computer only needs to record the values of each pixel at the time of conversion. The rasterization process is also necessary to display vector images on computer screens as monitors are made up of grids of pixels.