3.5.6.4 Bitmapped graphics.

Question 1

Outline how bitmaps represent an image.

Answer 1

An image is broken down into pixels, each of which has a binary value assigned to it.

Question 2

What do bitmap graphics represent?

Answer 2

An image.

Question 3

Explain the following for bitmaps: resolution.

Answer 3

Resolution is expressed as number of dots per inch where a dot is a pixel.

Question 4

What can resolution also refer to?

Answer 4

The number of pixels in an image.

Question 5

Explain the following for bitmaps: colour depth

Answer 5

The number of bits assigned to a pixel in its image.
In an image, if each pixel had been assigned one bit then this would allow four 2 (2^1) different colours to be represented.

If a colour depth of two bits were used, there would be four (22) different
colours that each pixel could take, represented by the bit patterns 00, 01, 10 and 11

Colour depth = number of bits stored for each pixel.

Question 6

What determines the colour of a pixel?

Answer 6

The value assigned to it.

Question 7

Define a pixel.

Answer 7

The smallest addressable part of a bitmap image.

Question 8

Explain the following for bitmaps: size in pixels

Answer 8

Size of an image in pixels is:

width of image in pixels x height of image in pixels.

Question 9

Explain how to calculate storage requirements for bitmapped images.

Answer 9

Ignoring metadata,

storage requirements = size in pixels x colour depth

where size in pixels is:

width in pixels x height in
pixels

Question 10

What must we be aware of when dealing with bitmap image files?

Answer 10

That they may contain metadata.

Question 11

Outline the typical metadata for bitmapped images.

Answer 11

Width.
Height.
Data created.
Colour depth.