HA1 Task 1 – Technical Glossary
Pixel
Pixel means Picture Element, and is the smallest controllable element of an image on a screen. Every pixel is a sample of an original image, so more samples will make the image more accurate. Some contexts use the word pixel to refer to 'a single scalar element of a multi-component representation'. When there are 1 million pixels, it is called a Megapixel, and 1000 megapixels make a Gigapixel.
LCD pixels are 'manufactured' in a 2D grid, and represented using squares or dots. CRT pixels correspond to their timing mechanisms and sweep rates.
The number of colours that can be represented by a pixel depends on the number of bits per pixel (bpp). A 1 bpp image uses 1-bit for every pixel, so each pixel can either be on or off. Every additional bit doubles the number of available colours.
1 bpp - 2 colours (Monochrome)
2 bpp - 4 colours
8 bpp - 256 colours
16 bpp - 65,536 colours (Highcolour)
24 bpp - 16,777,216 colours (Truecolour)
Colour Models – RGB and CMYK
The CMYK colour model is used in colour printing and to describe the printing process itself. CMYK refers to the 4 coloured inks used in some colour printing:
Cyan
Magenta
Yellow
Key
This model works by mixing colours on a light background. The ink reduces the light that would normally be reflected. A model like this is 'subtractive' because the inks 'subtract' brightness the from background.
The RGB model is used on a monitor or TV. This model is 'additive', because it adds colours to a black background, and the more colours you add, the lighter it gets. The primary colours are:
Red
Green
Blue
Resolution
Resolution is the number of pixels on a screen, and the detail of an image. This term applies to raster images, film images, etc. A higher resolution means more detail in an image. Basically, resolution means how close lines can be to each other and still be seen with the naked eye. The closer you are to a screen, the less detailed it may look, but if you stood away from the screen, it would look clearer.
Raster Images: file formats and uses - psd, bmp, gif, tiff, jpg, png
Raster/Bitmap images that are generally in a rectangular grid of pixels, or points of colour, which can be viewed on a monitor, paper or other displays.
File formats:
.psd - 'Photoshop document' A psd file store an image with support for most imaging options in Photoshop. A psd file has a maximum height and width of 30,000 pixels, and a
length limit of 2 Gigabytes.
.bmp - 'Bitmap image file' A bmp file is a format used to store bitmap digital images independent of the display device. This format is capable of storing 2D images, both monochrome and in colour, with various colour depths, and with optional data compression.
.gif - 'Graphics interchange format' This format can support up to 8 bits per pixel (bpp) for each image. It also supports animations and allows up to 256 colours per frame. It is well suited for simpler images like graphics or logos with solid areas of colour.
.tiff - 'Tagged Image File Format' This format is used for storing raster images, and is popular with graphics artists, many in the publishing industry, and both amateur and professional photographers.
.jpg - 'JPEG/Joint Photographic Experts Group(creators of the JPEG)' This format is a commonly used method of compressing digital images. The degree of compression is adjustable, allowing a trade-off between storage size and quality of an image. jpg uses 'lossy compression' (read below).
.png - 'Portable Network Graphics' The png format supports 'lossless compression' (read below). png was designed for transferring images on the internet and not for professional print graphics, so it doesn't support non-RGB colour spaces like CMYK.
Vector Images: file formats and uses - eps, wmf, fla, svg, ai
Vector images use simple geometric objects like points, lines, curves and shapes/polygons.
File formats:
.eps - 'Encapsulated PostScript' An eps file is a PostScript program, saved as a single file that includes a low resolution preview 'encapsulated' inside, allowing some programs to show a preview on the screen.
.wmf - 'Windows Metafile' The wmf format was originally designed for Microsoft Windows
in the 1990's. They are meant to be portable between different applications and can contain both vector and bitmap components.
.fla - 'Adobe Flash' fla files contain source material for the Flash application. 'Flash Authoring' software can edit fla files and convert them into swf files. This format is a binary file format based on the 'Microsoft Compound File Format'.
.svg - 'Scalable Vector Graphics' This format is used for 2D graphics with support for animation and interactivity. svg images can be created and editing using any text editor, but are more oftenly made using drawing software.
.ai - 'Adobe Illustrator Artwork' This format is used for representing single page vector based drawings in either the format of EPS or PDF.
Cross-platform Images: format and uses - pdf
Cross-platform is an 'attribute' given to computer software that can operate on multiple computer platforms. So that means a cross-platform images can also be used on multiple platforms.
Format:
.pdf - 'Portable Document Format' This format is used to present documents differently than other application software, hardware and operating systems. A pdf file shows a document with a fixed layout, including text, fonts, graphics and the other information required to display it.
Compression- lossy and lossless
Lossy - Lossy data compression means that when data is compressed, some of the data can be discarded. It allows the reconstruction of only an approximation of the original
data, though the the compression rate is usually improved, and the file size is reduced. Lossy compression is commonly used to compress multimedia data (audio, video & still images).
Lossless - Lossless data compression is when an image compresses, and when it gets decompressed it allows the original data to be perfectly reconstructed. This is used when it is important that the original and decompressed data is identical, usually compressed in a ZIP format.
Image Capture Devices – scanner, digital camera, tablet/smartphone
Regardless of which device it is, all of them contain image sensors and lens.
Scanner - A scanner is an object that optically scans images, printed text, an object or handwriting and converts it to a digital image.These are commonly used in offices as flatbed scanners where a document is placed on a glass window for scanning.
Digital Camera - A digital camera is a camera that takes pictures and videos digitally and stores them for later use. Digital and film cameras are similar, but digital cameras have an electrical image pickup device, whereas film cameras have chemical.
Tablet/Smartphone - A smartphone is a mobile phone with more advanced computing capability and connectivity than other basic feature phones. Early smartphones typically combined features of a phone with those of other popular consumer devices, like media players and cameras. Later smartphones contain all those plus the features of a touchscreen computer, like web browsing and Wi-Fi. A tablet is mobile computer with the display, circuitry and battery all within a single unit. Tablets can be equipped with sensors, including cameras, microphones and touch screen, with finger/stylus gestures replacing a mouse and keyboard.
Optimising
In relation to images/graphics, optimising is when artwork/an image is prepared for its final use. This may involve cropping, resizing, changing the file format & colour model. This all depends on what the image will be used for when it is finished, and must be considered at the beginning of designing.
Storage and Asset Management
Storing and organising artwork is extremely important, in terms of security. If it isn't handled securely then artwork can be stolen. Digital Asset Management (DAM) consists of management tasks and decisions about annotation, storage and retrieval of digital images. It can refer to the protocol for downloading, renaming, backing up, rating, grouping, archiving and exporting files.
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