Representing Images

Bitmap Images

A bitmap image is one which has been divided up into small areas call pixels, theses are the smallest possible blocks of colour in the image. Each pixel is then given a binary code which included its position on the image as well as its colour. When displaying a bitmap image the binary codes are first transferred from the file to the memory and then sent to the VDU where the image is pieces together and displayed. A VDU is also made up of pixels, the more of these the screen contains the high quality the image will be.

Vector Images

A vector graphic stores a image is a very different style to that of a bitmap, where as a bitmap stores each pixel a vector image converts the graphic into a series of mathematical algorithms that can be used to recreate the image. For example an image will first be broken down into usable components such as lines, circles and rectangles each with its own set of properties. A line would require a start and end coordinates, its width and colour, each of these would be converted to binary for storage. The major advantage for using vector graphics is the fact that they have no main resolution, meaning that the properties of the algorithms can be scaled when the image is increased in size and therefore there is no quality or sharpness loss.

Advantages of each

  • Images that contain a geometric style take up less space in vector format
  • Images with large areas of the same colour take up less space in bitmap format which is why they're preferred for camera images
  • Vector graphic don't lose any sharpness or quality when scale where as bitmaps do
  • Within vector graphics you can search for and edit specific shapes on their own

Resolution

Resolution refers to the number of pixels something has, this is expressed as the number per row by the number per column , for example 1920 by 1089 or 1280 by 720. However it isn't just the number of pixels but also their size which contribute to quality. An image that has a large pixel density but is small is size will have a sharper image than one that has a low pixel density but is larger. This is because as the size of the pixels increases it is far easier to spot them.