Vector Graphics

Vector Graphics are computer graphics images that are defined in terms of points on a Cartesian plane, which are connected by lines and curves to form polygons and other shapes. Vector graphics have the unique advantage over raster graphics in that the points, lines, and curves may be scaled up or down to any resolution with no aliasing.

The points determine the direction of the vector path; each path may have various properties including values for stroke color, shape, curve, thickness, and fill.

Vector Graphics Formats

Vector graphics are commonly found today in the SVG, EPS, PDF or AI types of graphic file formats, and are intrinsically different from the more common raster graphics file formats such as JPEG, PNG, APNG, GIF, and MPEG4.

What are vector graphics made up of?

Vector graphics can be created in a form using a pen plotter, a special type of printer that uses a series of ballpoint and felt-tip pens on a servo-driven mount that moves horizontally across the paper, with the plotter moving the paper back and forth through its paper path for vertical movement.

Vector graphics
Vector graphics

Although a typical plot might easily require a few thousand paper motions, back and forth, the paper doesn’t slip. In a tiny roll-fed plotter made by Alps in Japan, teeth on thin sprockets indented the paper near its edges on the first pass and maintained registration on subsequent passes.

Some Hewlett-Packard pen plotters had two-axis pen carriers and stationery paper (plot size was limited). However, the moving-paper H-P plotters had grit wheels (akin to machine-shop grinding wheels) which, on the first pass, indented the paper surface, and collectively maintained registration.

Present-day vector graphic files such as engineering drawings are typically printed as bitmaps, after vector-to-raster conversion. Vector graphics are ideal for simple or composite drawings that need to be device-independent, or do not need to achieve photo-realism.

Raster images, also known as bitmaps, are comprised of individual pixels of color. Each color pixel contributes to the overall image. Raster images might be compared to pointillist paintings, which are composed with a series of individually-colored dots of paint.

Each paint dot in a pointillist painting might represent a single pixel in a raster image. When viewed as an individual dot, it’s just a color; but when viewed as a whole, the colored dots make up a vivid and detailed painting. The pixels in a raster image work in the same manner, which provides for rich details and pixel-by-pixel editing.

Raster images are ideal for photo editing and creating digital paintings in programs such as Photoshop and GIMP, and they can be compressed for storage and web-optimized images.

Unlike raster graphics, which are comprised of colored pixels arranged to display an image, vector graphics are made up of paths or lines, each with a mathematical formula (vector) that tells the path how it is shaped and what color it is bordered with or filled by.

Since mathematical formulas dictate how the image is rendered, vector images retain their appearance regardless of size. They can be scaled infinitely. Vector images can be created and edited in programs such as Illustrator, CorelDraw, and InkScape.

                              Raster                             Vector
Comprised of pixels, arranged to form an image Comprised of paths, dictated by mathematical formulas
Constrained by resolution and dimensions Infinitely scalable
Capable of rich, complex color blends Difficult to blend colors without rasterizing
Large file sizes (but can be compressed) Small file sizes
File types include .jpg, .gif, .png, .tif, .bmp, .psd; plus .eps and .pdf when created by raster programs File types include .ai, .cdr, .svg; plus .eps and .pdf when created by vector programs
Raster software includes Photoshop and GIMP Vector software includes Illustrator, CorelDraw, and InkScape
Perfect for “painting” Perfect for “drawing”
Capable of detailed editing Less detailed, but offers precise paths

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