Digital Images

Question 1

What is the singular of ‘data’?

Answer 1

Datum

Question 2

What can image analysis be used for?

Answer 2

To calculate morphological parameters on a computer

Question 3

List the different types of radiation on the electorate-magnetic spectrum from the largest wavelength to the smallest.

Answer 3

Radio
Microwave
Infrared
Visible
Ultraviolet
X-ray
Gamma ray

Question 4

What is the wavelength of radio waves?

Answer 4

10^3

Question 5

What is the wavelength of microwaves?

Answer 5

10^-2

Question 6

What is the wavelength of infrared?

Answer 6

10^-5

Question 7

What is the wavelength of visible light?

Answer 7

0.5x10^-6

Question 8

What can image processing and analysis be used for in a biological context?

Answer 8

CT-scanner
CT slice
MRI
radiography
Counting objects (e.g. bacteria)

Question 9

How many bits in a byte?

Answer 9

8 bits are in a byte

Question 10

How many bytes are in a pixel?

Answer 10

A pixel = 1 byte

Question 11

What is a pixel?

Answer 11

a sample of light based in that particular position

Question 12

How many different combinations are there of 0 and 1 in a single byte?

Answer 12

256

Question 13

An image is a sequence of numbers ranging between 0 and _____

Answer 13

255 (not 256 because we start at 0)

Question 14

How many bytes does a greyscale image of size 800x600 occupy on the computer?

Answer 14

800x600= 480000 Bytes (480kB)

Because 1 pixel= 1 byte so an image of size MxN pixels occupies M x N Bytes

Question 15

Some images use more than 8 bits for storing grey levels. With 16 bits, how many different values of grey can a pixel assume up to?

Answer 15

2^16 = 65536 different values of grey

Question 16

How many Bytes does an RGB image of size 800x600 occupy on the computer?

Answer 16

800 x 600 x 3 = 1,440,000 Bytes (1.44 MB)

To get MB divide by 1 million

Question 17

What three colours are used in colour images?

Answer 17

Red, Green, Blue

Question 18

Image formation means?

Answer 18

Object in, image out (on computer)

Question 19

Image processing means?

Answer 19

Image in, image out

Question 20

Image analysis means?

Answer 20

Image in, features out (for example, area and perimeter)

Question 21

Computer graphics means?

Answer 21

Numbers in, image out

Question 22

Computer vision means?

Answer 22

Image in, interpretation out

Question 23

Visualisation means?

Answer 23

Image in, representation out

Question 24

What does the operation ‘image processing’ do?

Answer 24

1) Enhancement and restoration

2) segmentation (thresholding and edge detection)

Question 25

What does the operation ‘image analysis’ do?

Answer 25

Feature extraction and measuring

Question 26

Define binary image

Answer 26

A digital image that had only two possible values for each pixel

Question 27

Define image segmentation

Answer 27

The process of partitioning a digital image into multiple segments

Question 28

What is the goal of image segmentation?

Answer 28

To simplify/change the representation of an image into something simpler and easier to analyse

Question 29

Define image processing

Answer 29

The analysis and manipulation of a digitised image, especially in order to improve its quality

Question 30

Define image analysis

Answer 30

the extraction of meaningful information from images

Question 31

List some applications of image analysis (not necessarily biological)

Answer 31

1) to see the internal organisation of termite nests
2) co-localisation of markers in microscope images
3) counting trees in an oil palm plantation (via aerial image)

Question 32

What does dilation do?

Answer 32

Adds pixels to the edges of objects in a binary image

Question 33

What does erosion do?

Answer 33

Removes pixels form the edges of objects in a binary image

Question 34

What does watershed do?

Answer 34

Watershed segmentation is a way of automatically separating or cutting apart particles that touch

Question 35

What is a computer program?

Answer 35

A program is simply a sequence of instructions telling a computer what to do

Question 36

What is morphological filtering?

Answer 36

It is used to clean an image after segmenting it (it fills in holes, removes isolated background and foreground pixels etc)

Question 37

What does connected components labelling do?

Answer 37

It allows you to connect together pixels that belong to the same object

Question 38

Name two ways in which a high-level language can be translated into machine language which the computer can execute

Answer 38

You can either compile or interpret the language

Question 39

What does binarisation do?

Answer 39

It converts an image into black and white (background black, foreground white)

Question 40

Define grey level (or grey scale) image

Answer 40

A monochrome image in which pixels typically represent brightness values ranging from 0 to 255.

Question 41

Define restoration

Answer 41

Given a noisy sample of some true data, the goal of restoration is to recover the best possible estimate of the original true data.

Question 42

Define saturation

Answer 42

Reaching the upper limit of a dynamic range. For instance, intensity saturation occurs for an 8- bit monochromatic image when intensities greater than 255 are recorded: any such value is encoded as 255.

Question 43

Define thresholding

Answer 43

Thresholding is the quantization of an image into two values. One example is the conversion of a greyscale image to a binary image.