3 - Images
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How is a black-and-white image stored in binary?
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
What is a vector graphics program’s method of storing image data?
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
Name three properties stored for a circle object.
• Object type • Co-ordinates / location of the centre • Radius / diameter • Fill colour • Fill style • Line thickness • Line colour • Line style
What is meant by a pixel?
Picture element / smallest resolvable area/unit which can be drawn on screen / smallest addressable part/unit of a picture
How are pixels encoded to form a bitmapped image?
Pixels are stored as numbers/bit patterns which represent different colours
State two advantages of vector graphics compared with bitmap graphics.
• 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
What is meant by the resolution of a bitmapped graphic image?
The number of pixels / dots per cm / inch / unit of measurement
What is meant by the colour depth of a bitmapped graphic image?
The number of bits used to represent the colour / greyscale value