Computer Science AS · Information representation. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A bitmap image is a grid of pixels. Each pixel stores one colour as a binary number. The number of bits per pixel is the colour depth, and the number of pixels in the image is the image resolution. A file header stores details such as the width, height and colour depth.
A vector graphic stores no pixels. It stores a drawing list of drawing objects (line, circle, rectangle), each with properties such as position, size and colour. It can be enlarged without losing quality.
Sound is analogue. To store it, the amplitude of the wave is measured at regular intervals. This is sampling. More samples per second and more bits per sample give a more accurate recording and a bigger file.
Students forget to divide by 8 and give the answer in bits when the question asks for bytes. Always check the unit asked for before choosing an option.
Answer: The file size is 4 MiB.
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