Imagine the smiley face in the top left corner as an RGB bitmap image. The smiley, smiley face, or happy face, is a stylized representation of a smiling human face commonly represented as a yellow circle with two dots representing When zoomed in, it might look like the big smiley face to the right. Every square represents a pixel. Zooming in further, the individual pixels can be analyzed, with their colors constructed by adding the values for red, green and blue.

In computer graphics, a raster graphics image or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data In Computer graphics, a bitmap or pixmap is a type of memory organization or Image file format used to store Digital images The A data structure in Computer science is a way of storing Data in a computer so that it can be used efficiently In Geometry, a rectangle is defined as a Quadrilateral where all four of its angles are Right angles A rectangle with vertices ABCD would be denoted as In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Paper is thin material mainly used for writing upon printing upon or packaging Raster images are stored in image files with varying formats (see Comparison of graphics file formats). Image file formats are standardized means of organising and storing images This is a comparison of Image file formats. General Ownership of the format and related information

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). Color depth. or bit depth, is a Computer graphics term describing the number of Bits used to represent the Color of a single Pixel

The printing and prepress industries know raster graphics as contones (from "continuous tones") and refer to vector graphics as "line work". Printing is a process for reproducing text and image typically with ink on Paper using a printing press Prepress is the term used in the Printing and Publishing industries for the processes and procedures that occur between the procurement of a written manuscript and Vector graphics is the use of geometrical primitives such as points lines, Curves and shapes or Polygon (s which are all based

The word "raster" has its origins in the Latin rastrum (a rake), which is derived from 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.

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. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. 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. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication 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. Vector graphics is the use of geometrical primitives such as points lines, Curves and shapes or Polygon (s which are all based Geometry ( Greek γεωμετρία; geo = earth metria = measure is a part of Mathematics concerned with questions of size shape and relative position In Mathematics, the concept of a curve tries to capture the intuitive idea of a geometrical one-dimensional and continuous object In Geometry a polygon (ˈpɒlɨɡɒn ˈpɒliɡɒn is traditionally a plane figure that is bounded by a closed path or circuit

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. Vector quantization is a classical Quantization technique from Signal processing which allows the modeling of probability density functions by the distribution of The green component sometimes has more bits than the other two to allow for the human eye's greater discrimination of this component. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain

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. Image resolution describes the detail an Image holds The term applies equally to Digital images film images and other types of images Color depth. or bit depth, is a Computer graphics term describing the number of Bits used to represent the Color of a single Pixel 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 compression is the application of Data compression on Digital images In effect the objective is to reduce redundancy of the image data in order to be able to A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original but is close enough to be useful

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. Vector graphics is the use of geometrical primitives such as points lines, Curves and shapes or Polygon (s which are all based Rendering is the process of generating an image from a model, by means of computer programs 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. Typesetting involves the presentation of textual material in graphic form on Paper or some other medium. The term graphic design can refer to a number of artistic and professional disciplines which focus on visual communication and presentation 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. Dots per inch ( DPI) is a measure of spatial Printing or Video dot density in particular the number of individual dots that can be placed within the span Typically, a resolution of 150 to 300 pixel per inch works well for 4-color process (CMYK) printing. CMYK (short for '''c'''yan, '''m'''agenta, '''y'''ellow, and k ey ( Black) and often referred to as process color

See also

• Dither
• Halftone
• GIS file formats
• Posterization
• Raster image processor
• Rasterisation

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. Dither is an intentionally applied form of Noise, used to randomize Quantization error, thereby preventing large-scale patterns such as contouring that are more objectionable Halftone is the Reprographic technique that simulates Continuous tone imagery through the use of equally spaced dots of varying size A GIS file format is a standard of encoding geographical information into a file Posterization (pronounced Poe-ster-ize-ation of an image occurs when a region of an image with a continuous gradation of tone is replaced with several regions of fewer tones resulting A raster image processor (RIP is a component used in a Printing system which produces a raster image also know as a Bitmap. Rasterization or Rasterisation is the task of taking an image described in a Vector graphics format (shapes and converting it into a Raster image ( The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software