Storing images

Question 1

What is colour depth?

Answer 1

Colour depth is the number of bits used for each pixel.

Question 2

What is image resolution?

Answer 2

Image resolution is the number of pixels in the image. This is width x height

Question 3

What is a bitmap?

Answer 3

A bitmap is an image made up of pixels.

Question 4

What is a disadvantage of having more colours in your picture?

Answer 4

A disadvantage is that it takes up more storage as you require more bits to make up the image.

Question 5

What equation is required to work out the file size in bits?

Answer 5

File size(bits) = image resolution(width x height) x colour depth

Question 6

How many colours are in an image with 4-bits?

Answer 6

There are 16 colours as it is 2^4

Question 7

Calculate the file size in MB of an 4-bit image that is 1500 pixels wide and 1400 pixels high

Answer 7

1.05MB because you first have to use the formula to find the size in bits which is 8.4 million and then you divide by 8 to find the size in bytes and then divide by 1000 twice to get it in megabytes.

Question 8

What is the formula for calculating the total number of colours in an image?

Answer 8

2^n(where n = number of bits per pixel, or bpp)

Question 9

Calculate the file size in MB of an 8-bit image that is 2000 pixels wide and 2500 pixels high

Answer 9

5MB as you use the formula to find the size in bits which is 40 million and then you divide by 8 to get it in bytes and then by 1000 twice so get it in megabytes which equals 5