Vector graphics
Vector graphics are a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display and printing hardware, vector data models and file formats, as well as the software based on these data models (especially graphic design software, computer-aided design, and geographic information systems). Vector graphics are an alternative to raster or bitmap graphics, with each having advantages and disadvantages in specific situations.[1]
While vector hardware has largely disappeared in favor of raster-based monitors and printers,[2] vector data and software continue to be widely used, especially when a high degree of geometric precision is required, and when complex information can be decomposed into simple geometric primitives. Thus, it is the preferred model for domains such as engineering, architecture, surveying, 3D rendering, and typography, but is entirely inappropriate for applications such as photography and remote sensing, where raster is more effective and efficient. Some application domains, such as geographic information systems (GIS) and graphic design, use both vector and raster graphics at times, depending on purpose.
Vector graphics are based on the mathematics of analytic or coordinate geometry, and is not related to other mathematical uses of the term vector. This can lead to some confusion in disciplines in which both meanings are used.
Data model
The logical data model of vector graphics is based on the mathematics of coordinate geometry, in which shapes are defined as a set of points in a two- or three-dimensional cartesian coordinate system, as p = (x, y) or p = (x, y, z). Because almost all shapes consist of an infinite number of points, the vector model defines a limited set of geometric primitives that can be specified using a finite sample of salient points called vertices. For example, a square can be unambiguously defined by the locations of three of its four corners, from which the software can interpolate the connecting boundary lines and the interior space. Because it is a regular shape, a square could also be defined by the location of one corner, a size (width=height), and a rotation angle.
The fundamental geometric primitives are:
- A single point.
- A line segment, defined by two end points, allowing for a simple linear interpolation of the intervening line.
- A polygonal chain or polyline, a connected set of line segments, defined by an ordered list of points.
- A polygon, representing a region of space, defined by its boundary, a polyline with coincident starting and ending vertices.
A variety of more complex shapes may be supported:
- bezigons.
- Standard parametric shapes in two or three dimensions, such as circles, ellipses, squares, superellipses, spheres, tetrahedrons, superellipsoids, etc.
- Irregular three-dimensional surfaces and solids, are usually defined as a connected set of polygons (e.g., a NURBS).
- Fractals, often defined as an iterated function system.
In many vector datasets, each shape can be combined with a set of properties. The most common are visual characteristics, such as color, line weight, or dash pattern. In systems in which shapes represent real-world features, such as GIS and BIM, a variety of attributes of each represented feature can be stored, such as name, age, size, and so on.[3]
In some Vector data, especially in GIS, information about
If a dataset stored in one vector file format is converted to another file format that supports all the primitive objects used in that particular image, then the conversion can be lossless.
Vector display hardware
Vector-based devices, such as the vector CRT and the pen plotter, directly control a drawing mechanism to produce geometric shapes. Since vector display devices can define a line by dealing with just two points (that is, the coordinates of each end of the line), the device can reduce the total amount of data it must deal with by organizing the image in terms of pairs of points.[5]
Vector graphic displays were first used in 1958 by the
Subsequent vector graphics systems, most of which iterated through dynamically modifiable stored lists of drawing instructions, include the
Plotters used in technical drawing still draw vectors directly to paper by moving a pen as directed through the two-dimensional space of the paper. However, as with monitors, these have largely been replaced by the wide-format printer that prints a raster image (which may be rendered from vector data).
Software
Because this model is useful in a variety of application domains, many different software programs have been created for drawing, manipulating, and visualizing vector graphics. While these are all based on the same basic vector data model, they can interpret and structure shapes very differently, using very different file formats.
- Graphic design and illustration, using a vector graphics editor or graphic art software such as Adobe Illustrator. See Comparison of vector graphics editors for capabilities.
- Geographic information systems (GIS), which can represent a geographic feature by a combination of a vector shape and a set of attributes.[9] GIS includes vector editing, mapping, and vector spatial analysis capabilities.
- Computer-aided design (CAD), used in engineering, architecture, and surveying. Building information modeling (BIM) models add attributes to each shape, similar to a GIS.
- 3D computer graphics software, including computer animation.
File formats
Vector graphics are commonly found today in the
The
In recent years, SVG has become a significant format that is completely independent of the resolution of the rendering device, typically a printer or display monitor. SVG files are essentially printable text that describes both straight and curved paths, as well as other attributes. Wikipedia prefers SVG for images such as simple maps, line illustrations, coats of arms, and flags, which generally are not like photographs or other continuous-tone images.[citation needed] Rendering SVG requires conversion to a raster format at a resolution appropriate for the current task. SVG is also a format for animated graphics.
There is also a version of SVG for mobile phones. In particular, the specific format for mobile phones is called SVGT (SVG Tiny version). These images can count links and also exploit anti-aliasing. They can also be displayed as wallpaper.
CAD software uses its own vector data formats, usually proprietary formats created by software vendors, such as
Conversion
To raster
Modern displays and printers are
From raster
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Printing
Vector art is ideal for
If we regard typographic characters as images, then the same considerations that we have made for graphics apply even to the composition of written text for printing (
Operation
Advantages of this style of drawing over raster graphics:
- Because vector graphics consist of coordinates with lines/curves between them, the size of representation does not depend on the dimensions of the object. This minimal amount of information translates to a much smaller[13] file size compared to large raster images which are defined pixel by pixel. This said, a vector graphic with a small file size is often said to lack detail compared with a real world photo.
- Correspondingly, one can infinitely zoom in on e.g., a circle arc, and it remains smooth. On the other hand, a polygon representing a curve will reveal being not really curved.
- On zooming in, lines and curves need not get wider proportionally. Often the width is either not increased or less than proportional. On the other hand, irregular curves represented by simple geometric shapes may be made proportionally wider when zooming in, to keep them looking smooth and not like these geometric shapes.
- The parameters of objects are stored and can be later modified. This means that devices.
- From a 3-D perspective, rendering shadows is also much more realistic with vector graphics, as shadows can be abstracted into the rays of light from which they are formed. This allows for photorealistic images and renderings.
For example, consider a circle of radius r.[14] The main pieces of information a program needs in order to draw this circle are
- an indication that what is to be drawn is a circle
- the radius r
- the locationof the center point of the circle
- stroke line style and color (possibly transparent)
- fill style and color (possibly transparent)
Vector formats are not always appropriate in graphics work and also have numerous disadvantages.[15] For example, devices such as cameras and scanners produce essentially continuous-tone raster graphics that are impractical to convert into vectors, and so for this type of work, an image editor will operate on the pixels rather than on drawing objects defined by mathematical expressions. Comprehensive graphics tools will combine images from vector and raster sources, and may provide editing tools for both, since some parts of an image could come from a camera source, and others could have been drawn using vector tools.
Some authors have criticized the term vector graphics as being confusing.[16][17] In particular, vector graphics does not simply refer to graphics described by Euclidean vectors.[18] Some authors have proposed to use object-oriented graphics instead.[16][19][20] However this term can also be confusing as it can be read as any kind of graphics implemented using object-oriented programming.[16]
Vector operations
Vector graphics are ideal for simple or composite drawings that need to be device-independent, use a vector graphics model.
See also
- Animation
- Anti-Grain Geometry
- Cairo (graphics)
- Comparison of vector graphics editors
- Comparison of graphics file formats
- Computer-aided design
- Direct2D
- Illustration
- Javascript graphics library
- Raster to vector
- Raster graphics
- Resolution independence
- Turtle graphics
- Vector game
- Vector graphics file formats
- Vector monitor
- Vector network
- Vector packs
- Vexel
- Wire frame model
- 3D modeling
Notes
- ISBN 0-471-98386-1.
- ISBN 978-3-540-56787-5.
- ^ Vector Data Models Archived April 11, 2022, at the Wayback Machine, Essentials of Geographic Information Systems, Saylor Academy, 2012
- ^ Bolstad, Paul (2008). GIS Fundamentals: A First Text on Geographic Information Systems (3rd ed.). Eider Press. p. 37.
- ^ Murray 2002, pp. 81–83.
- (PDF) from the original on April 18, 2021. Retrieved July 31, 2020.
- hdl:10919/63920. Retrieved September 18, 2020.
- ISBN 978-0-313-33868-7. Retrieved July 31, 2020.
- .
- ^ Gharachorloo et al. 1989, p. 355.
- ^ "Vector & Raster Graphics in Offset Printing". Olympus Press. December 6, 2013. Archived from the original on February 12, 2014. Retrieved June 16, 2014.
- ^ "Printing and Exporting (Graphics)". COE Unix Network. June 18, 2002. Archived from the original on February 6, 2014. Retrieved June 16, 2014.
- ^ "PNG vs. SVG: What are the differences?". Adobe. Retrieved December 12, 2023.
- ^ "ASCIIsvg: Easy mathematical vector graphics". Peter Jipsen, Chapman University. Archived from the original on September 16, 2013. Retrieved June 16, 2014.
- ^ Andy Harris. "Vector Graphics". Welcome to wally!!!. Archived from the original on May 18, 2012. Retrieved June 16, 2014.
- ^ ISBN 0-471-98386-1.
- ^ CS 354 Vector Graphics & Path Rendering Archived April 18, 2020, at the Wayback Machine, Slide 7, By Mark Kilgard, April 10, 2012, University of Texas at Austin
- ISBN 978-1-4302-2739-7.
- ISBN 978-0-201-69963-0.
- ISBN 978-1-133-41950-1.
- ^ Barr 1984, p. 21.
- ^ SVG Working Group (March 15, 2011). "SVG Compositing Specification". w3. Archived from the original on August 7, 2022. Retrieved August 8, 2022.
- hdl:10012/4262. Archived(PDF) from the original on July 28, 2020. Retrieved July 28, 2020.
References
- Barr, Alan H. (July 1984). "Global and local deformations of solid primitives" (PDF). Proceedings of the 11th annual conference on Computer graphics and interactive techniques. Vol. 18. pp. 21–30. S2CID 16162806. Retrieved July 31, 2020.
- Gharachorloo, Nader; Gupta, Satish; S2CID 8253227. Retrieved July 28, 2020.
- Murray, Stephen (2002). "Graphic Devices". In Roger R. Flynn (ed.). Computer Sciences, Vol 2: Software and Hardware, Macmillan Reference USA. Gale eBooks. Retrieved August 3, 2020.
External links
- Media related to Vector graphics at Wikimedia Commons