Technical GlossaryPixel resolution• The image that is displayed on the screen is composed of thousands (or millions) of small dots; theseare called pixels; the word is a contraction of the phrase "picture element". A pixel represents thesmallest piece of the screen that can be controlled individually. Each one can be set to a differentcolour and intensity (brightness).• The number of pixels that can be displayed on the screen is referred to as the resolution of the image;this is normally displayed as a pair of numbers, such as 640x480. The first is the number of pixels thatcan be displayed horizontally on the screen, and the second how many can be displayed vertically.The higher the resolution, the more pixels that can be displayed and therefore the more that can beshown on the monitor at once, however, pixels are smaller at high resolution and detail can be hardto make out on smaller screens. Resolutions generally fall into predefined standard sets; only a fewdifferent resolutions are used by most PCs.• The aspect ratio of the image is the ratio of the number of X pixels to the number of Y pixels. Thestandard aspect ratio for PCs is 4:3, but some resolutions use a ratio of 5:4. Monitors are calibrated tothis standard so that you can draw a circle and have it appear to be a circle and not an ellipse.Displaying an image that uses an aspect ratio of 5:4 will cause the image to appear somewhatdistorted. The only mainstream resolution that currently uses 5:4 is the high-resolution 1280x1024.• There is some confusion regarding the use of the term "resolution", since it can technically meandifferent things. First, the resolution of the image you see is a function of what the video card outputsand what the monitor is capable of displaying; to see a high resolution image such as 1280x1024requires both a video card capable of producing an image this large and a monitor capable ofdisplaying it. Second, since each pixel is displayed on the monitor as a set of three individual dots (red,green and blue), some people use the term "resolution" to refer to the resolution of the monitor, andthe term "pixel addressability" to refer to the number of discrete elements the video card produces.In practical terms most people use resolution to refer to the video image, as I do on this site.Vector and raster images• There are two kinds of computer graphics - raster (composed of pixels) and vector (composed ofpaths). Raster images are more commonly called bitmap images.• A bitmap image uses a grid of individual pixels where each pixel can be a different color or shade.Bitmaps are composed of pixels.• Vector graphics use mathematical relationships between points and the paths connecting them todescribe an image. Vector graphics are composed of paths.• The image to the left below is representative of a bitmap and the image to the right is representativeof a vector graphic. They are shown at four times actual size to exaggerate the fact that the edges of abitmap become jagged as it is scaled up:File formats and uses• Bmp- The BMP file format, also known as bitmap image file or device independent bitmap (DIB) fileformat or simply a bitmap, is a raster graphics image file format used to store bitmap digital images,independently of the display device (such as a graphics adapter), especially on Microsoft Windowsand OS/2 operating systems• Png- Portable Network Graphics (PNG pron.: /ˈpɪŋ/PING) is a Raster graphics file format thatsupports lossless data compression. PNG was created as an improved, non-patented replacement forGraphics Interchange Format (GIF), and is the most used lossless image compression format on theWorld Wide Web.
• Gif-The Graphics Interchange Format (GIF; /ˈdʒɪf/ or /ˈɡɪf/) is a bitmap image format that wasintroduced by CompuServe in 1987 and has since come into widespread usage on the World WideWeb due to its wide support and portability. The format supports up to 8 bits per pixel thus allowing asingle image to reference a palette of up to 256 distinct colours. The colours are chosen from the 24-bit RGB colour space. It also supports animations and allows a separate palette of 256 colours foreach frame. The colour limitation makes the GIF format unsuitable for reproducing colourphotographs and other images with continuous colour, but it is well-suited for simpler images such asgraphics or logos with solid areas of colour.• Tiff-TIFF (originally standing for Tagged Image File Format) is a file format for storing images,popular among graphic artists, the publishing industry, and both amateur and professionalphotographers in general. As of 2009, it is under the control of Adobe Systems. Originally created bythe company Aldus for use with "desktop publishing", the TIFF format is widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, faxing, wordprocessing, optical character recognition and other applications. Adobe Systems, which acquiredAldus, now holds the copyright to the TIFF specification. TIFF has not had a major update since 1992,though several Aldus/Adobe technical notes have been published with minor extensions to theformat, and several specifications, including TIFF/EP (ISO 12234-2), TIFF/IT (ISO 12639), TIFF-F (RFC2306) and TIFF-FX (RFC 3949) have been based on the TIFF 6.0 specification.• Jpg-In computing, JPEG is a commonly used method of loss compression for digital photography(image). The degree of compression can be adjusted, allowing a selectable trade off between storagesize and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in imagequality.• Psd-Photoshop files have default file extension as .PSD, which stands for "Photoshop Document." APSD file stores an image with support for most imaging options available in Photoshop. These includelayers with masks, colour spaces, ICC profiles, CMYK Mode (used for commercial printing),transparency, text, alpha channels and spot colours, clipping paths, and duotone settings. This is incontrast to many other file formats (e.g. .JPG or .GIF) that restrict content to provide streamlined,predictable functionality. A PSD file has a maximum height and width of 30,000 pixels, and a lengthlimit of 3 Gigabytes.• Pdf-Portable Document Format (PDF) is a file format used to represent documents in a mannerindependent of application software, hardware, and operating systems. Each PDF file encapsulates acomplete description of a fixed-layout flat document, including the text, fonts, graphics, and otherinformation needed to display it. In 1991, Adobe Systems co-founder John Warnock outlined a systemcalled "Camelot" that evolved into PDF.• Eps-Encapsulated PostScript file. A file format commonly used for photographic and drawn graphics.An EPS file is created and later placed onto a page layout in a page assembly program.• Ai-Adobe Illustrator Artwork (AI) is a proprietary file format developed by Adobe Systems forrepresenting single-page vector-based drawings in either the EPS or PDF formats. The .ai filenameextension is used by Adobe Illustrator.CompressionIn computer science and information theory, data compression, source coding, or bit-ratereduction involves encoding information using fewer bits than the original representation.Compression can be either lossy or lossless. Lossless compression reduces bits by identifyingand eliminating statistical redundancy. No information is lost in lossless compression. Lossycompression reduces bits by identifying unnecessary information and removing it. Theprocess of reducing the size of a data file is popularly referred to as data compression,although its formal name is source coding (coding done at the source of the data before it isstored or transmitted).
Compression is useful because it helps reduce resources usage, such as data storage spaceor transmission capacity. Because compressed data must be decompressed to use, this extraprocessing imposes computational or other costs through decompression; this situation isfar from being a free lunch. Data compression is subject to a space-time complexity trade-off. For instance, a compression scheme for video may require expensive hardware for thevideo to be decompressed fast enough to be viewed as it is being decompressed, and theoption to decompress the video in full before watching it may be inconvenient or requireadditional storage. The design of data compression schemes involves trade-offs amongvarious factors, including the degree of compression, the amount of distortion introduced(e.g., when using lossy data compression), and the computational resources required tocompress and uncompress the data.Image capture devicesImage Capture is an application program from Apple that enables users to upload pictures from digitalcameras or scanners which are either connected directly to the computer or the network. It provides noorganizational tools like iPhoto but is useful for collating pictures from a variety of sources with no need fordrivers.Image Capture is scriptable with AppleScript, and may be manipulated with Mac OS X v10.4 (Tiger)s"Automator" application. As of Mac OS X 10.4, Image Captures AppleScript dictionary does not open in ScriptEditor. As of Mac OS X 10.6 only the Image Capture Web Server opens in Script Editor.OptimisingIn computer science, program optimization or software optimization is the process of modifying a softwaresystem to make some aspect of it work more efficiently or use fewer resources. In general, a computerprogram may be optimized so that it executes more rapidly, or is capable of operating with less memorystorage or other resources, or draw less power.Storage and managementComputer data storage, often called storage or memory, is a technology consisting of computer componentsand recording media used to retain digital data. It is a core function and fundamental component ofcomputers. The central processing unit (CPU) of a computer is what manipulates data by performingcomputations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive andsmall storage options close to the CPU and slower but larger and cheaper options farther away. Often the fast,volatile technologies (which lose data when powered off) are referred to as "memory", while slowerpermanent technologies are referred to as "storage", but these terms can also be used interchangeably. In theVon Neumann architecture, the CPU consists of two main parts: control unit and arithmetic logic unit (ALU).The former controls the flow of data between the CPU and memory; the latter performs arithmetic and logicaloperations on data.IT asset management (ITAM) is the set of business practices that join financial, contractual and inventoryfunctions to support life cycle management and strategic decision making for the IT environment. Assetsinclude all elements of software and hardware that are found in the business environment.IT asset management (also called IT inventory management) is an important part of an organizations strategy.It usually involves gathering detailed hardware and software inventory information which is then used to makedecisions about hardware and software purchases and redistribution. IT inventory management helpsorganizations manage their systems more effectively and save time and money by eliminating unnecessarypurchases and wasted resources.