A raster graphic is an image composed entirely of single pixels to create a larger, more detailedimage. You would typically expect images from cameras, screenshots and the web to be made up ofseparate pixels. There are many file formats which will be used to save raster images, althoughtypically the most common formats would be .jpg, .jif, .png . Each of the corresponding formats willbe used for a different purpose. A Fantastic example of a raster image would be large pixel artportraits, like the one pictured below:Although at a distance the picture appears to be very high in detail, however on closer inspection itis very clear that the image is composed of many smaller pixels that have been carefully placed sothat at a further distance, the image becomes much clearer and appears to have more detail.Raster images are resolution dependant, this means as the image is scaled up, and the size of bothplanes will determine the resulting quality. This means they cannot be scaled up to an arbitrary sizewithout loss of detail and pixilation. For example an image that is 1000x1000 would look perfect atits native resolution (1000x1000), however if this image was then scaled up to 2000x2000 it wouldcreate dramatic amounts of pixilation and distortion, resulting in an unusable image.Some of the advantages of Raster Graphics: The image is typically much more compatible than a vector. Each location of each cell holding a pixel is implied by its position in the cell matrix. This means other than an origin point, no geographic coordinates are stored. Quick to perform and easy to program. Easy to create.Some of the disadvantages of Raster Graphics:
Images can be scaled but with a distinct loss in image quality, so typically the size a raster image is taken in, will be the size it stays forever. They require higher resolutions and anti-aliasing for smooth appearences. Some formats not compatible with other operating systems.Raster ApplicationsPaint:Firstly it is important to know what you are going to be using the final graphic for and what you needfrom the editing software. Typically if you only want to do extremely primitive editing such ascropping, free-hand drawing or small typographay based pictures a program such as Paint willsuffice.Photoshop:Photoshop is widely considered one of the mose powerful and feature rich raster image editingpackages available on the market. There is a plethora of tools which can take years to completelymaster and come to terms with. There is a multitude of different tools such as: Pen tools Filters Gradient Fills In-Depth text editing Hundreds of image and colour adjustments Masking And thousands more...Lossy compressionLossy Compression eliminates “unnecessary” bits of information, changing thefile so that it becomes smaller. This type of compression is used commonly forreducing the size of bitmap pictures, which are usually quite large in size.Typically, a substantial amount of data can be discarded before the result issufficiently degraded to be noticed by the user, this is very useful as you canlower the file size a fair amount and save space without any problems. Files arecompressed to reduce the overall size and this make them more suitable to usefor streaming mediums I.E an internet gallery..jpeg images can be saved at different compression rates and thus altering thefile size, and also unfortunately lowering the overall quality of the image, thereis a definite loss of colour reproduction and also quality, as you lose largeamount of detail.
Lossy compression works by “Discarding” data that is less neccicary. In photos this can be thingssuch as deep blacks, whites and relative colours that are near each other, for example in the aboveimage, this is why you will find images “layering” the colours in an image, for example the threeimages opposite have all been altered in quality, with the best one at the top, and the worst at thebottom. You can see layering in the sky of the bottom picture.Vector GraphicsVector Graphics use “geometrical primitives” and mathematical equations to keep the qualityextremely consistent, not matter how much zoom or expansion is placed on that particular image. Vectoring does this by applying mathematical equations to ever shape placed into the particular image, to constantly resize the shape and create a smooth undeviating line whenever it is resized or expanded. Since these formulas can produce an image scalable to any size and detail, the quality of the image is limited only by the resolution of the display, and the file size of vector data generating the image stays the same. Vectors can be particularly useful as there is never a loss of quality, and a consistent image is always portrayed, no matter what zoom or stretch is applied to the image. The drawback to using vector graphics is that they are more processorintensive than raster images, meaning this inherently limits the functionality for large data sets.Points are a mathematical plot in the vector image. These are saved in relation to where the otherpoints are. They are used to bridge the gap between another point and the lines that join them.Lines are the items used to go in-between the points, these are called paths and they aredetermined by where the points are.Typically Vector images are saved in the following file formats:Ai:The Adobe illustrator file is a common file type used for saving vector images. It is one of the mostwidely used graphic design programs. It has a file with the tag AI, meaning that this is the fileoriginally used for developing the vector image design. These files can almost always be opened byAdobe Illustrator programs exclusively and cant be brought into other applications.EPS:EPS stands for Encapsulated PostScript. Surprisingly, it can contain both vector and bitmap data.PostScript Is the universal language used for computer printers and also professional printers. If thefile contains only vectors it can easily be reduced or enlarged without loss of resolution and is thebest file to use for printing logos or vector graphics.
SVG:SVG or Scale Vector Graphics File is a family of an XML-based file format. Similarly to the rest of thevector file formats it allows for unlimited scaling.Vector ApplicationsAdobe Fireworks:Fireworks is a vector and bitmap graphics editor. Typically you would associate Fireworks with webediting due to the fact it has image splicing in order to reduce load times and also includes mayother features which would be of use to the budding web designer.Adobe Illustrator:Illustrator is a vector specific application which shares a few qualities with Photoshop, this is mainlydue to the fact both Photoshop and Illustrator are made by the same company, Adobe. Thisprogram would be for the “high end” user, although typically vectors should not be created oraltered by people who don’t know what they are doing as it is distinctly more difficult that dealingwith Raster images. Illustrator features things such as: Pen and line tools Live trace Live paint Gradients Layers Lots more...MetafilesMetafiles is a bracket term used for a file format that can contain both Raster & Vector images,commonly graphics formats. These files can contain Raster, Vector and Type Deta. There are a fewdifferent file formats used to save metafiles, with the most common being a PDF (PortableDocument Format). Another format that you would associate with Metafiles would be SVG orScalable Vector Graphic(s). There are some key things to do with Metafiles which are worth noting,they are: Mobile Can host both Raster and Vector Widely compatible Common
When saving a file it is important to know wether or not you’re going to need a metafile, this willtypically depend on what the final use of the graphic file will be. If there is no reason to use aMetafile it would be more sensible to use a Raster or Vector. There are a number of different programs you can use to edit and create Metafiles. The mostcommon of these would probably be Photoshop, however adobe also has Illustrator for creating amix of Raster and Vector..svg Scalable Vector Graphics (SVG) is an XML-based vector image format for two-dimensional graphicsthat has support for interactivity and animation. This format is used by all majorinternet browsers such as Chrome, Firefox, Opera and Safari, and can mark up directly. .svg is able toinclude Raster, Vector and Text which makes it useful for creating lots of various things..PDF This format is quite possibly the most well known and highly distributed form of Metafile, it is usedin lots of online documents and is the product of Adobe Systems, created in 1993. Each PDF fileencapsulates a complete description of a fixed-layout flat document, including the text, fonts,graphics, and other information needed to display it.