Definition: Vector Image

Vector images | Glossary entry

Vector images

Components of new pictures are produced by the actions of an artist or draftsman. Creating a line or a brush stroke, makes a unique mark which has individual characteristics. Each component created in this way is described by a mathematical equation in a vector image.

The mathematical equations define how pixels are coloured and where they are placed on the screen. Each brush stoke, drawn line or shape has a mathematical model to describe its characteristics. These individual components can all be redefined mathematically through that model. In this way components can be resized, re-shaped or transformed without damage or quality loss.

The nature of vector images

The individual components of each part of the vector image are retained separately. As such they can be manipulated, changed, scaled and transformed. The fact that these components are all separate makes vector images uniquely suitable for the creation of precise drawings, diagrams or images. The individual parts can be worked and placed with great precision to match the needs of the overall vector image.

Vector graphics definition of each separate component is based on vectors or ‘paths’. These paths are groups of pixels on the screen that are themselves defined by nodes. The nodes are points on the paths that can be selected by a cursor and dragged to new sizes, shapes and dimensions. In effect the individual components of the vector image is a graphic that has changeable properties according to what type of shape it is.

At the base level, all vector graphics are primitive graphical objects. They are composed of lines, curvy shapes and geometric shapes like circles, triangles and squares etc. Custom shapes with both curves and lines can also be constructed. The shapes can be filled so they appear solid. Alternatively they can be textured, coloured and made into custom shapes that gives infinite variety to their appearance.

The individual vector graphics in a vector image are well defined. The use of the pixels in the screen is precisely calculated. The vector image retains its relative position and defined shape even if scaled to a new size. Because each shape is defined precisely in a mathematical way scaling does not affect quality. Smaller and larger screen implementations of a line stroke or shape can be recalculated to ensure precise replication of the shape in a new size.

Using vector images

Each component of the vector image is constructed in computer using application tools in response to unique guidance by the draftsman. Vector images are suited to creating unique graphics according to design. Vector editors are specialized editors, for graphics, computer aided design (CAD), or artwork. These tools are not suited to replicating the real world like raster images are when they are created from a digital image sensor.

Editing vector images

The type of editor used for vector images is quite specific to that image form. The tools that are used may appear similar to those in a raster editor, but they have specific mathematical functions. The editing of vector images involves intense and precise mathematical formulations of the lines and shapes that are created. Creating an object on the screen requires the application to create a specific mathematical object and maintain it separately from all the other components. Each edit is also a change to the object as a whole.

Objects created in a vector image editor are separate from all the other objects in the image. However, they may be added to, combined, locked together and manipulated in groups and as families of objects. These edit tools are sophisticated and tend to be specific to the tools which created them.

The separate nature of the vector image objects in the image makes them unique entities within the image file. This is quite unlike a raster file where the image is the result of the viewed state of all the pixels combined. So it is no surprise that the tools used to create and edit these different file types are unique to the type of file being edited.

Vector images and raster images in the same editor

The different file formats are normally separated. However, like spread sheets and word processors, they can be partially mixed. Sophisticated image editors are able to create “raster” layers for raster images and likewise for vector images. It is possible to do this by creating ‘layers’ which do not mix the two types of graphical object. To mix or merge them they will first have to be converted to the same type. Thus, in an image editor that is of raster image type, the vector image objects will have to be “rasterized” to create the final file.

Comparison – raster image format and vector image format

For a comparison between the two types of file view this table.

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Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photographer and editor of this site. He has also run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.
See also: Editors ‘Bio’.
By Damon Guy see his profile on Google+.

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