Dealing with Images
Images fall into two categories; bitmap(raster) and vector images. You may never have heard of these terms, but they are important when working with images.
Bitmap (or raster) images
Bitmap images are typically photo-realistic images. Theyuse a grid of colours known as pixels to represent images. Each pixel is assigned a specific location and colour value. For example, look at the three-bird image. You can see that at its highest magnification the bitmap image is made up of a mosaic (tiles) of pixels. When working with bitmap images, you edit the pixel rather than the objects or shapes.
Bitmap images are resolution-dependent; that is, they contain a fixed number of pixels. As a result, they can lose detail and appear jagged when they are magnified too much, or when they are resized to a size larger than what they were intended to be seen at.
Paint programs are used to create bitmap graphics. They have many advantages: they are cheap, easy to learn and very good for changing small parts of a graphic because each pixel can be edited. However, the graphics produced have a more jagged appearance and use a lot of storage space, and it isn’t easy to move parts of a picture without changing the rest of the picture. The jagged appearance can be smoothed out by a process called –anti-aliasing where edge pixels are blended into the background using shades of the adjoining pixels.
Vector images
Vector imagesare images that consist of lines, shapes, curves, and solid blocks of colour and/or text. Together these elements can be constructed to create images but they tend to be cartoon-like (clip art). Vector objectsare displayed according to geometric (mathematical) characteristics and are resolution-independent – thatis, they can be resized to any size and printed atany resolution without losing detail. Vector images areunsuitable for producing photo-realistic images.
Draw programsare used to create vector graphics. Draw programs use a range of basic objects called primitives to create pictures. These primitives include lines, rectangles, circles, curves and shapes. The images produced are usually more accurate, clearer, and needing less storage space to store them. It is easier to change or move small parts of an image than it is using Paint programs, because each of the primitives can be changed without affecting other parts of the image. Also primitives can be grouped allowing you to work with multiple objects at the same time, and then ungrouped to work with the individual objects. Pictures produced with Draw programs can also be morphed and easily resized without loss of details. Unlike painting, drawing effects like shading and adding fine details aremuch harder to do.
Activity 1
(A) Look at these images and determine if they are a bitmap or a vector image.
Delete the incorrect term
/ /Bitmap / Vector / Bitmap / Vector / Bitmap / Vector
/ /
Bitmap / Vector / Bitmap / Vector / Bitmap / Vector
(B In the table below are various scenarios. Place a tick (<Insert<Symbol<Wingdings>) in the most likely graphic application you would use to meet the needs of the particular scenario.
Scenario / Bitmap (Paint) / Vector (Draw)Generally uses less memory to store a digital image
It produces smoother lines and curves
Images are typically life-like
Images can be morphed into other shapes
Images have jagged edges, especially when resized
Parts of the image can be grouped together
Images are mathematical representations of objects
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