Posted by admin on 28th April 2010


There are two different types of images that we can create or edit on a computer and the difference is how they are stored.

Bitmap images

Bitmap images (or raster graphics) are made up of pixels which are little squares or dots of colour. The resolution of an image tells you how many dots there are in the picture. Most computer screens are at least 1000 pixels wide, so you can get an idea of image size from that. The higher the resolution of an image, the better it will look.

How a bitmap image gets "pixellated"

When a small picture, say 100 pixels wide, is stretched to fill the whole screen it will look fuzzy or blocky – you will be able to see each individual pixel.

Cameras take Bitmap images – and that’s why the camera resolution is measured in MegaPixels – a mega pixel is a million individual dots of colour in the whole photo. Bitmap images may be stored as .bmp fiels, but nowadays more likely as a .jpg or .png file. Pictures with millions of pixels can end up as several megabytes – even with filetypes like .jpg which compress the size of the picture to save disk space.

Photo editing software is very popular and common – you can even get software like Picassa, and Gimp for free, offering incredible effects and editing power. They allow you to change the colour of individial pixels (or lots at once) to get the effect you want on your picture.

Vector Graphics

Vector images are made from lines, points and filled in shapes. Rather than dots, each image is stored as the instructions needed to re-draw it. A vector image is not good for photo-realism, but images like cartoons are ideal. The exact shapes mean that a vector image can be enlarged as much as you want, with the lines staying exactly sharp and precise, no fuzzy bits or pixellation. They’re also really good for storing blueprints and designs for CAD-CAM, as the precise instructions ensure that exactly the right shape is made.

See the difference when zooming an image as a vector and as a bitmap

As our computer screens display images with pixels of colour, vector graphics files need to be converted to be displayed. Often, the vector file is later saved as a bitmap image once the designer has decided how big it should be. Vector files are usually stored in the special file format of the program used to create them – perhaps .ai for Adobe Illustrator, or .svg for several other programs. Inkscape is a vector graphics program which you can download for free.

    1 Response

  1. james says:

    i think this was helpfull

Post your comments