A bitmap image is 40 pixels wide and 30 pixels high. It has a colour depth of 4 bits.
(a) Calculate the file size of the image in bytes. Ignore any metadata. Show your working. [3]
(b) State how many different colours can be used in the image. [1]
(c) The colour depth is increased to 8 bits. State the effect on the file size. [1]
- (a) 40 × 30 (= 1200 pixels)(1)
- (a) × 4 (= 4800 bits) and ÷ 8(1)
- (a) 600 (bytes)(1)
- (b) 16(1)
- (c) The file size doubles; allow it becomes 1200 bytes(1)
- Answer: (a) 600 bytes (b) 16 (c) doubles (to 1200 bytes)
- Examiner tip: File size = width × height × colour depth gives BITS – divide by 8 for bytes.