A-level Computing/AQA/Paper 2/Fundamentals of data representation/Vectors

Bitmaps Comparison between vector and bitmaps Vector Graphics images defined using mathematics and geometry such as points, lines, curves, and shapes or polygon(s). Allowing for scalability. Objects and properties stored mathematically. Drawing list a set of commands used to define a vector image If you enjoy messing about with SVGs take a look at inkscape Vector graphics are made up of objects and their properties. An object is a mathematical or geometrically defined construct such as a rectangle, line or circle. <rect ... /> <line ... /> <circle ... /> Each of these objects has properties to tell you the size, colour, position etc. Take a look at the next example to see how drawing lists are built from objects and properties. Rectangle Circle Combination Image border border border DrawingList<rect x="14" y="23" width="250" height="50" fill="green" stroke="black" stroke-width="1" /><circle cx="100" cy="100" r="50" fill="red" stroke="black" stroke-width="5" /> <rect width="100" height="80" x="0" y="70" fill="green" /> <line x1="5" y1="5" x2="250" y2="95" stroke="red" /> <circle cx="90" cy="80" r="50" fill="blue" /> <text x="180" y="60"> Un texte </text> Notes x and y give the top left start location Note that the centre co-ordinate is defined through cx and cyr gives the radius Note that the circle is on top, this is because it was drawn last.To leave out an edge stroke don't put the stroke command in.The line has start x1,y1 and end x2,y2 coordinates. 6 Extension:SVG There are several vector graphic formats out there, but an easy one to get started with is Scalable Vector Graphics (SVGs). SVGs are very easy to create and are supported by all modern major web browsers. To create an SVG, you need to add the tags <svg xmlns="http://www.w3.org/2000/svg"> at the beginning and <code></svg></code> at the end. Copy the following into a text file and save it as image.svg <svg xmlns="http://www.w3.org/2000/svg"> <rect width="100" height="80" x="0" y="70" fill="green" /> <line x1="5" y1="5" x2="250" y2="95" stroke="red" /> <circle cx="90" cy="80" r="50" fill="blue" /> <text x="180" y="60"> Un texte </text> </svg> Once you have saved this, drag it into a browser window and you should see some shapes. SVGs are very powerful and you can attach code to their structure, making them interactive. If you want to learn more about how make SVGs take a look at w3schools 1 Exercise: Vector Graphics What is a drawing list a set of commands used to define a vector image Give some objects that can be used in vector graphics: Line Text Rectangle Circle Give the properties needed to display a rectangle: x,y width, height fill stroke (colour), stroke-width Give the properties needed to display a line: x1,y1 - start coordinates x2,y2 - end coordinates width fill stroke (colour) Give the definition of a vector image: images defined using mathematics and geometry such as points, lines, curves, and shapes or polygon(s). Allowing for scalability Write a drawing list to create the following image: center|400px <rect width="1" height="1" x="2" y="1" fill="white" <!--optional you can leave this out--> stroke="black" stroke-width=1 /> <!--another small value will do--> <rect width="1" height="1" x="11" y="0" fill="white" <!--optional you can leave this out--> stroke="black" stroke-width=1 /> <rect width="10" height="4" x="2" y="6" fill="black" stroke="red" stroke-width=5 /> <!--another small value will do--> <circle cx="7" cy="5" r="2" fill="blue" /> What would the following drawing list produce: <line x1="0" y1="0" x2="6" y2="6" stroke="red" /> <rect width="4" height="4" x="1" y="1" fill="yellow" stroke="green" stroke-width=1 /> <line x1="6" y1="0" x2="0" y2="6" stroke="black" /> File:CPT-Graphics-VectorList2.svg In the above code, name the objects involved rect and line In the above code, list 4 different properties Fill Stroke Stroke-width Width Height X,Y