Paul is a GIS professor at Vancouver Island U, has a PhD from U of British Columbia, and has taught stats and programming for 15 years.
Use of Images
Many types of documents use images to illustrate a product or concept. Presentations, in particular, will become much more interesting when you have effective visuals. For example, a presentation on the marketing for a product is likely going to have an image of the product itself. When describing the manufacturing process of a product, you may want to include a diagram that shows the steps in the production process.
There are a number of specialized software applications to create and edit images, including illustration software and photo-editing software. In general, these applications work with two types of images: vector graphics and raster graphics.
Vector graphics consist of illustrations created using line work. In technical terms, you use points, lines, curves and shapes to create the illustration. Vector graphics are based on vectors, also referred to as paths. You can think of drawing with a pencil as the process of creating vectors, since you are drawing lines.
One of the key characteristics of a vector graphic is that the line work is sharp, even when you zoom in very closely. In a computer application, the line work is stored as a mathematical formula that describes the exact shape of the line. So when you zoom in, you are seeing the line in more detail but it remains a line.
You can alter how vector graphics look by changing the properties of the line and by filling in the area between the lines. This can turn a set of simple black and white lines into a great illustration. When you see a photo-realistic illustration that is not actually a photograph, the illustration typically consists of a very detailed vector graphic containing hundreds or thousands of lines.
Vector graphics are created and edited using illustration software. There are a number of different illustration applications. One of the most widely used ones is Illustrator by Adobe. Others include CorelDraw by the Corel Corporation and the open source applications Inkscape and Xara Xtreme. Vector graphics can be stored in a number of different file formats, including AI, EMF, SVG and MWF.
Raster graphics consist of illustrations created using pixels. In technical terms, you use a rectangular grid of cells of equal size and each cell has its own color. These cells are also called pixels. Raster graphics are also called bitmaps. Digital photographs are the most common type of raster graphics.
Digital photographs in general are raster graphics. If you have a digital camera, you may know that it uses a certain number of megapixels. This refers to the number of pixels used for a single picture. A defining characteristic of a raster graphic is that when you zoom in very closely, you start to see the actual pixels.
An important property of a raster graphic is its resolution. Resolution indicates the amount of detail, so a higher resolution means more detail. You can achieve a higher resolution by using more pixels, which is why a larger number of megapixels for a digital camera results in sharper photographs.
For example, a digital photograph of 800 (horizontal) by 600 (vertical) pixels uses 480,000 pixels total. A digital photograph of 2,048 by 1,536 pixels uses 3,145,728 pixels or 3.1 megapixels. This provides a lot of more detail to represent the object being photographed. However, more pixels also means that more data storage is needed and high resolution digital photography can take up a lot of storage space.
Raster graphics are manipulated using photo-editing software. One of the most widely used ones is Photoshop by Adobe. Other ones are PhotoPlus X6 and Aperture. A popular open source application is GIMP. Raster graphics can be stored in a number of different file formats, including BMP, GIF, JPEG, PNG and TIFF.
Vector vs. Raster
Both vector and raster are widely used for illustrations. In fact, when you see an illustration, you may not recognize which of the two formats is used until you zoom in very closely. In general, most illustrations created from scratch by an illustrator or graphic designer use vector, while images collected using a digital camera use raster. In addition, many vector graphics are exported to raster format at high resolution to make them easier to work with in other software applications. So, an illustrator may create a detailed line drawing in illustration software, but the final image in a report may consist of a raster version of that illustration.
Software applications work with two types of images: vector graphics and raster images. Vector graphics consist of illustrations created using line work. You can think of drawing with a pencil as the process of creating vectors. One of the key characteristics of a vector graphic is that the line work is sharp, even when you zoom in very closely. Vector graphics are created and edited using illustration software.
Raster graphics consist of illustrations created using pixels. Raster graphics are also called bitmaps. Digital photographs are the most common type of raster graphics. A defining characteristic of a raster graphic is that when you zoom in very closely, you start to see the actual pixels. Raster graphics are manipulated using photo-editing software.
After this lesson, you should be able to:
- Summarize how vector graphics and raster graphics are created
- Identify the defining characteristics of vector and raster graphics
- List examples of each type of graphic
- Compare and contrast these two types of graphics
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