01 Representing Images

Question 1

How does a camera capture an image

Answer 1

• it breaks up what it sees into a grid of pixels
• a light sensor measures the intensity of colour in each pixel
• each measurement is converted into a binary code using analogue-to-digital converter

Question 2

Affect of number of pixels recorded

Answer 2

Number of bits used and file size

Question 3

Bitmapped raster graphics

Answer 3

Created using a grid of pixels
Each pixel is give a colour value

Question 4

Common bitmap file types

Answer 4

BMP
JPG
GIF
PNG
TIF

Question 5

Resolution

Answer 5

The number of pixels used to make up a bitmap image
Width x height

Question 6

Effect of resolution on image size

Answer 6

Resolution doesnt define the size of an image
If an image is made bigger or smaller the size of each pixel grows or shrinks to maintain the required resolution

Question 7

Creating an image

Answer 7

Each pixel is given a binary value
Each value represents a different colour

Question 8

Increasing the number of colours

Answer 8

More bits per pixel = more colour combinations
1 bit = 2
2 bits = 4
3 bits = 8
4 bits = 16

Question 9

Variation in quality

Answer 9

Changing the colour depth of an image will affect the number of colours it can display

Question 10

Calculating file size

Answer 10

Determined by the number of pixels used and the number of colour combinations available
Quality is traded off against file size

file size = pixels used x colour depth

to convert to bytes divide value by 8

Question 11

examples of meta data

Answer 11

Data
Width and height
Colour depth
GPS coordinates