HA1 - Technical File – Raster images. A raster image, also called a bitmap is a way to represent digital images. The raster image takes a wide variety of formats. A raster image represents an image in a series of bits of information which translate into pixels on the screen. These pixels form points of colour which create an overall finished image. When a raster image is created the image on the screen is converted into pixels and each pixel is assigned a specific value which determines its colour. When a raster image is viewed, the pixels usually smooth out visually for the user who sees a photograph or drawing, when blown up the pixels in a raster image become apparent. Depending on resolution, some raster images can be enlarged to very large sizes, while others quickly become difficult to see. The smaller the resolution, the smaller the digital image file, for this reason people who work with computer graphics must find a balance between resolution and image size. Resolution refers to the number of pixels per inch (PPI) or dots per inch (DPI) in the image. The higher the resolution the greater the number of pixels, this allows a greater radiation of colour that will translate better as the image is enlarged. The more pixels, the more individual points of data to be stored, as well. For high quality photography, a high DPI is preferred because the images will look more appealing to the viewer. For small images which do not need to be blown up, or when quality is not important, a low DPI can be used http://www.wisegeek.com/what-is-a-raster-image.htm
HA1 - Technical File – Vector images <ul><li>Vector graphics is the use of geometrical primitives such as lines, curves, points and shapes or polygons which are all based on mathematical equations to represent images in computer graphics. </li></ul><ul><li>These are instances where working with vector tools and formats is the best practice. There are times when both formats come together. An understanding of the advantages and limitations of each technology and the relationship between them is most likely to result in efficient and effective use of tools. </li></ul><ul><li>Vector graphics formats are complementary to raster graphics, which is the representation of images as an array of pixels as its typically used for the representations of photographic images Vector graphics are stored as mathematical expressions as opposed to bit mapped graphics which are stored as a series of mapped 'dots', also known as pixels (picture cells) There are instances when working with vector tools and formats is the best practice, and instances when working with raster tools and formats is the best practice. </li></ul><ul><li>Vector formats are not always appropriate in graphics work because devices such as cameras and scanners produce raster graphics that are impractical to convert into vectors. </li></ul>This example shows the effect of vector graphics versus raster graphics> The original vector based illustration is the one shown at the left. The lower right image illustrates the same magnification as a bitmap image. Vector images can be scaled indefinitely without degrading quality.
Anti-aliasing. <ul><li>In digital signal processing, spatial anti-aliasing is the technique of minimizing the distortion artefacts known as aliasing when representing a high resolution image at a lower resolution. Anti-aliasing is used on digital photography, computer graphics, digital audio, and many other applications. </li></ul><ul><li>Anti-aliasing means removing signal components that have higher frequency than is able to be properly resolved by the recording (or sampling) device. The removal is done before sampling at a lower resolution. When sampling is preformed without removing this part of the signal, it causes undesirable artefacts such as the black and white noise near the top of figure 1-a below. </li></ul>Above left: an aliased version of a simple shape. Above right: an anti-aliased version of the same shape. Right: The anti-aliased graphic at 5x magnification. In this approach, the ideal image is regarded as a signal . The image displayed on the screen is taken as samples, at each ( x,y ) pixel position, of a filtered version of the signal. Ideally, we would understand how the human brain would process the original signal, and provide an image on screen that will yield the most similar response by the brain
Image Resolution Image resolution describes the detail an image holds. The term applies to raster digital images, film, images, and other different types of images. Higher resolution means more image detail. Image resolution can be measured in various ways. Basically resolution quantifies how close lines can be to each other and still be visibly removed. Resolution units can be tried to physical sizes to the overall size of the picture or to angular subtenant. Line pairs are often used instead of lines, a line pair compromises a dark line and an adjacent line. A resolution of ten lines per millimetre. Photographic lens and film resolution are most often quoted in line pairs per millimetre. Spatial Resolution: The measure of how closely lines can be resolved in an image is called spatial resolution, and it depends on properties of the system creating the image, not just the pixel resolution in pixels per inch. A classic test target used to determinate spatial resolution of imaging sensors and imaging sensors.
Aspect Ratio. The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is for an x:y aspect ratio, no matter how big or small the image is, the width is divided into x units of equal length and the height is measured using the same length unit, the height will be measured to be y units. Aspect ratios are mathematically expressed as x:y and Xxy with the letter particularly used for pixel dimensions. Cinematographic aspect ratios are usually denoted as a decimal multiple of width vs. unit height. The most common aspect ratios used today in the presentation of films in movie theatres are 1.85:1 and 2.39:1 5 common aspect ratios:
File Formats A file format is a particular way in which information is encoded for storage in a computer file. GIF is a file format that should not really be used for prepress, it is far more suited for web design or to exchange images through e-mail or newsgroups. The JPEG File Interchange Format (JFIF) is an image file format standard. It is a format for exchanging JPEG encoded files compliant with the JPEG interchange format ( JIF ) standard. It solves some of JIF' s limitations in regard to simple JPEG encoded file interchange. TIFF or the Tagged Image File Format is a file format that is strictly used for bitmap data. TIFF files don’t contain text or vector data, even though the file format theoretically would permit additional tags to handle such data EPS or Encapsulated PostScript is a standard graphics file format for exchanging images, drawings (such as a logo or map) or even layouts of complete pages. PSD is a proprietary file format used to create and edit images in Adobe Photoshop. It is a widely accepted format as it supports all available image types – Bitmap, RGB, Duotone, Gray scale, Indexed Color, CMYK, Lab, and Multichannel. Portable Document Format ( PDF ) is an open standard for document exchange. This file format, created by adobe systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems.
Color models. A color model is am abstract mathematical model by describing the way colours can represented as tuples of numbers, typically as three or four values or colour components. When the model is associated with a precise description of how the components are to be interpreted. RGB Color Model Recognizing that the geometry of the RGB model is poorly aligned with the color-making attributes recognized by human vision, computer graphics researchers developed two alternate representations of RGB, HSV and HSL. HSV and HSL improve on the color cube representation of RGB by arranging colors of each hue in a radial slice, around a central axis of neutral colors which ranges from black at the bottom to white at the top. The fully saturated colors of each hue then lie in a circle, a colour wheel. CMYK Colour Model The CMYK color model ( process color , four color ) is a subtractive colour model used in colour printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan , magenta , yellow , and k ey (black). Color printing typically uses ink of four colors: cyan, magenta, yellow, and key (black
Adobe Photoshop Adobe photoshop is a graphics editing program developed and published by Adobe Systems incorporated. Adobe Photoshop is released in two editions: Adobe Photoshop , and Adobe Photoshop Extended , with the Extended having extra 3D image creation, motion graphics editing, and advanced image analysis features. Features Photoshop uses color models RGB, lab, CMYK, greyscale, binary bitmap, and duotone. Photoshop has the ability to read and write raster and vector image formats such as .EPS, .PING, .GIF, and .JPEG. Photoshop has ties with other Adobe software for media editing, animation, and authoring. Photoshop has ties with other Adobe software for media editing, animation, and authoring.
Adobe Illustrator Adobe Illustrator is a vector graphics editor developed and marketed Adobe Systems. Illustrator is similar in scope, intended market, and functionality to its competitors, Corel Draw and Macromedia Free Hand. Among the new features included in Illustrator CS2 were Live Trace, Live Paint, a control palette and custom workspaces. Live Trace allows for the conversion of bitmap imagery into vector art and improved upon the previous tracing abilities. Live Paint allows users more flexibility in applying color to objects, specifically those that overlap. In the same year as the CS2 release, Adobe Systems announced an agreement to acquire Macromedia in a stock swap valued at about $3.4 billion and it integrated the companies' operations, networks, and customer-care organizations shortly thereafter. Adobe now owned FreeHand along with the entire Macromedia product line and in 2007, Adobe announced that it would discontinue development and updates to the FreeHand program. Instead, Adobe would provide tools and support to ease the transition to Illustrator. Features
Adobe Indesign Adobe InDesign is a software application produced by Adobe Systems. It can be used to create works such as posters, flyers, brochures, magazines, newspapers and books. In conjunction with Adobe Digital Publishing Suite InDesign can publish content suitable for tablet devices. Graphic designers and production artists are the principal users, creating and laying out periodical publications, posters, and print media. It also supports export to EPUB and SWF formats to create digital publications, and content suitable for consumption on tablet computer devices. The Adobe in copy word processor uses the same formatting engine as InDesign.