O-LevelComputer ScienceData Representation2210/12 · May/June 2025 · Q29 Marks

A student has an image file stored on their computer.

(a)The image file was taken by a digital camera. Tick (✔) one box to show whether a digital camera is an example of an input, output, process or storage device. A input B output C process D storage[1]
(b)(i)The size of the image file is 3072 bytes. Give the size of the image file in kibibytes (KiB).[1]
(b)(ii)State the number of nibbles in 1 byte. Working space[1]
(c)(i)The image file has a colour depth of 32 bits. State what is meant by a colour depth of 32 bits.[1]
(c)(ii)The colour depth of the image file is changed to 64 bits. Explain what effect this change has on the image file.[2]
(d)The student uses lossless compression to compress the image file. Explain how the image file is compressed using lossless compression.[3]

Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

[1] A
[1] 3
[1] 2
[1] 32 bits are used to represent each/a/one colour in the image // 232 (approx. 4.3 billion) different colours can be used/are available for the image
[2] Any two from: • The size of the image file increases. • ... as the number of bits used to represent/store a colour has increased
[3] Any three from: • The size of the file is reduced without permanently removing any data. • A compression algorithm is used. • such as Run length encoding/RLE. • Repeating pixels are grouped/identified ... // Patterns are identified ... • and stored with the number of times they are repeated. • and indexed

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