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Encyclopedia > Raster graphics
Imagine the smiley face in the top left corner as an RGB bitmap image. When zoomed in, it might look like the big smiley face to the right. Every square represents a pixel. Zooming in further, one can analyze three individual pixels, with their colors constructed by adding the values for red, green and blue.

In computer graphics, a raster graphics image, digital image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a computer monitor, paper, or other display medium. Raster images are commonly stored in image files with varying formats. Image File history File links No higher resolution available. ... For other uses of smiley and smiley face, see Smiley (disambiguation). ... This article is about the scientific discipline of computer graphics. ... A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. ... This article is about the storage organization of raster images. ... A binary tree, a simple type of branching linked data structure. ... In geometry, a rectangle is defined as a quadrilateral where all four of its angles are right angles. ... This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ... Color is an important part of the visual arts. ... A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record. ... For other uses, see Paper (disambiguation). ... See also Category:Graphics file formats Here is a summary of the most common graphics file formats: Some file formats, e. ...


A bitmap corresponds bit-for-bit with an image displayed on a screen, generally in the same format used for storage in the display's video memory, or maybe as a device-independent bitmap. Bitmap is technically characterized by the width and height of the image in pixels and by the number of bits per pixel (a color depth, which determines the number of colors it can represent). This article is about the storage organization of raster images. ... Color depth is a computer graphics term describing the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. ...


The printing and prepress industries know raster graphics as contones (from "continuous tones") and refer to vector graphics as "line work". For other uses, see Print. ... Prepress. ... Example showing effect of vector graphics versus raster graphics. ...


The word "raster" has its origins in Latin rastrum (a rake) and Latin radere (to scrape), and recalls metaphorically the systematic sampling of a grid-pattern of individual pixel-spaces with a view to representing an overall image.

Contents

Colors

Each pixel has an individually defined color; images in the RGB color space, for instance, often consist of colored pixels defined by three bytes — one byte each for red, green and blue. Less colorful images require less information per pixel; for example, an image with only black and white pixels requires only a single bit for each pixel. One can distinguish raster graphics from vector graphics in that vector graphics represent an image through the use of geometric objects such as curves and polygons. A representation of additive color mixing—In CRT based (analog electronics) television three color electron guns are used to stimulate such an arrangement of phosphorescent coatings of the glass, the resultant reemission of photons providing the image seen by the eye. ... In computer science a byte (pronounced bite) is a unit of measurement of information storage, most often consisting of eight bits. ... BIT is an acronym for: Bannari amman Institute of Technology Bangalore Institute of Technology Beijing Institute of Technology Benzisothiazolinone Bilateral Investment Treaty Bhilai Institute of Technology - Durg Birla Institute of Technology - Mesra Battles in Time (Doctor Who magazine) BIT International College, formerly the Bohol Institute of Technology in Bohol, Philippines... Example showing effect of vector graphics versus raster graphics. ... Calabi-Yau manifold Geometry (Greek γεωμετρία; geo = earth, metria = measure) is a part of mathematics concerned with questions of size, shape, and relative position of figures and with properties of space. ... In mathematics, the concept of a curve tries to capture the intuitive idea of a geometrical one-dimensional and continuous object. ... Look up polygon in Wiktionary, the free dictionary. ...


A colored raster image (or pixmap) will usually have pixels with between one and eight bits for each of the red, green, and blue components, though other color-encodings also occur, such as four- or eight-bit indexed representations that use vector quantization on the (R, G, B) vectors. The green component sometimes has more bits than the other two to allow for the human eye's greater discrimination of this component. Vector quantization is a classical technique from signal processing, originally used for data compression, which provides a method for modeling probability density functions by the distribution of prototype vectors. ... For other uses, see Eye (disambiguation). ...


Encoding

The total number of pixels (resolution), and the amount of information in each pixel (often called color depth) determine the quality of a raster image. For example, an image that stores 24 bits of color-information per pixel (the standard for displays since around 1995) can represent smoother degrees of shading than one that only stores 16 bits per pixel, but not as smooth as one that stores 48 bits. Likewise, an image sampled at 640 x 480 pixels (and therefore containing 307,200 pixels) will look rough and blocky compared to one sampled at 1280 x 1024 (1,310,720 pixels). Because it takes a large amount of data to store a high-quality image, computer software often uses data compression techniques to reduce this size for images stored on disk. Some techniques sacrifice information, and therefore image quality, in order to achieve a smaller file-size. Computer scientists refer to compression techniques that lose information as "lossy" compression. Image resolution describes the detail an image holds. ... Color depth is a computer graphics term describing the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. ... Sampling may refer to: Sampling (signal processing), converting a continuous signal into a discrete signal Sampling (music), re-using portions of sound recordings in a piece Sampling (statistics), selection of observations to acquire some knowledge of a statistical population Sampling (case studies), selection of cases for single or multiple case... “Source coding” redirects here. ... Image compression is the application of Data compression on digital images. ...


Resolution

Raster graphics are resolution dependent. They cannot scale to an arbitrary resolution without loss of apparent quality. This deficiency contrasts with the capabilities of vector graphics, which easily scale to the quality of the device rendering them. Raster graphics deal more practically than vector graphics with photographs and photo-realistic images, while vector graphics often serve better for typesetting or for graphic design. Modern computer-monitors typically display about 72 to 130 pixels per inch (PPI), and some modern consumer printers can resolve 2400 dots per inch (DPI) or more; determining the most appropriate image resolution for a given printer-resolution can pose difficulties, since printed output may have a greater level of detail than a viewer can discern on a monitor. Typically, a resolution of 150 to 300 pixel per inch works well for 4-color process (CMYK) printing. Example showing effect of vector graphics versus raster graphics. ... This article does not cite any references or sources. ... This article or section is in need of attention from an expert on the subject. ... Graphics are often utilitarian and anonymous,[1] as these pictographs from the US National Park Service illustrate. ... The square shown above is 200 pixels by 200 pixels. ... Dots per inch (DPI) is a measure of printing resolution, in particular the number of individual dots of ink a printer or toner can produce within a linear one-inch (2. ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ...


See also

Dither is a form of noise, or erroneous signal or data which is deliberately added to sample data for the purpose of minimizing quantization error. ... Left: halftone spots. ... This is a comparison of graphics file formats. ... A GIS file format is a standard of encoding geographical information into a file. ... An example of a photo in JPEG format (24bit colour or 16. ... A raster image processor (RIP) is a component used in a printing system which produces a bitmap. ... Example showing effect of vector graphics versus raster graphics. ...

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. This article does not cite any references or sources. ... “GFDL” redirects here. ...


  Results from FactBites:
 
Raster graphics (0 words)
Raster graphics are the only reasonable choice for photos and satellite images.
Vector graphics can be converted to a raster graphic with a specified resolution, as is almost always the case before printing, except for "pen plotters".
Raster graphics cannot be converted back to vector graphics.
Web Graphics (805 words)
Please see the W3C Graphics Activity statement to find out what W3C is currently doing and has already done in the area of Web Graphics, including SVG, WebCGM Profile, and PNG.
SVG, a vector graphics format designed at W3C, written in XML and stylable with CSS, is starting to become a popular choice for including graphics in XML documents.
The IMG element is the most common method for using graphics in HTML pages.
  More results at FactBites »

 
 

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