Image Types (Edexcel IGCSE ICT)

Bitmaps & vectors

• Computers represent all data in binary, including images that are seen on a screen, TV or other output device 

• Images can be stored in binary as Bitmap or Vector

What is a bitmap?

• A bitmap image is made up of squares called pixels

• A pixel is the smallest element of a bitmap image

• Each pixel is stored as a binary code

• Binary codes are unique to the colour in each pixel

• A typical example of a bitmap image is a photograph

• The more colours and more detail in the image, the higher the quality of the image and the more binary that needs to be stored

What is a vector?

• A vector image is created from mathematical equations and points

• Only the mathematics used to create the image are stored

• For example, to create a circle the data stored would be:

  • Centre point (x, y coordinates)

  • Radius

• Typical examples of vector images are logos and clipart

• Vector images are infinitely scalable

• Ideal for situations where the same image will be made bigger and smaller and a loss of quality is unacceptable. For example, the same logo used on both a pencil and a billboard

Editing images

What is image editing?

• Image editing is the process of modifying and enhancing digital photographs, illustrations or any other visual media

Placing an image with precision

• This refers to positioning an image accurately within a document or other media

  • You can usually do this by selecting the image and dragging it to the desired location

  • Some software allows for more precision through the use of coordinates or alignment tools

Resizing an image

• This means changing the dimensions of an image

  • You can often do this by selecting the image and dragging its corners or edges

  • Maintaining the aspect ratio means the image's width and height change at the same rate, preventing distortion

  • Adjusting the aspect ratio can change the shape and proportions of the image

Cropping an image

• This involves cutting out and discarding parts of an image

  • Cropping tools usually allow you to select a portion of the image to keep and discard the rest
    

Rotating an image

• This means turning the image around a central point

  • Most software allows rotation to any angle, and common rotations such as 90 degrees or 180 degrees are often provided as options
    

Reflecting (flipping) an image

• This means creating a mirror image of the original

  • An image can be flipped horizontally (left to right) or vertically (top to bottom)
    

Grouping and layering images

• These techniques help to organise multiple images

  • Grouping combines images so they can be moved or transformed as a single unit

  • Layering involves placing images on top of each other

  • You can change the order of layered images, moving them to the front or back