3 - Images

Question 1

How is a black-and-white image stored in binary?

Answer 1

Image broken down into separate pixels
Each pixel is either black or white / on or off
Use 2 different values for black and white / 1 for black and 0 for white (or vice versa)
Store in one bit / bits / byte of computer memory

Question 2

What is a vector graphics program’s method of storing image data?

Answer 2

Drawing is made up of drawing objects, e.g. circle, rectangle, straight line
Different objects have a defined set of properties
Objects are stored as drawing commands / drawing list
Some properties use mathematical equations / formulae

Question 3

Name three properties stored for a circle object.

Answer 3

• Object type
• Co-ordinates / location of the centre
• Radius / diameter
• Fill colour
• Fill style
• Line thickness
• Line colour
• Line style

Question 4

What is meant by a pixel?

Answer 4

Picture element / smallest resolvable area/unit which can be drawn on screen / smallest addressable part/unit of a picture

Question 5

How are pixels encoded to form a bitmapped image?

Answer 5

Pixels are stored as numbers/bit patterns which represent different colours

Question 6

State two advantages of vector graphics compared with bitmap graphics.

Answer 6

• Individual objects can be manipulated independently
• Fewer bytes are used to represent an image
• The image can be scaled without loss of quality
• No ‘hole’ is left if an object is deleted

Question 7

What is meant by the resolution of a bitmapped graphic image?

Answer 7

The number of pixels / dots per cm / inch / unit of measurement

Question 8

What is meant by the colour depth of a bitmapped graphic image?

Answer 8

The number of bits used to represent the colour / greyscale value