Digital Images Flashcards
What is the singular of ‘data’?
Datum
What can image analysis be used for?
To calculate morphological parameters on a computer
List the different types of radiation on the electorate-magnetic spectrum from the largest wavelength to the smallest.
Radio Microwave Infrared Visible Ultraviolet X-ray Gamma ray
What is the wavelength of radio waves?
10^3
What is the wavelength of microwaves?
10^-2
What is the wavelength of infrared?
10^-5
What is the wavelength of visible light?
0.5x10^-6
What can image processing and analysis be used for in a biological context?
CT-scanner CT slice MRI radiography Counting objects (e.g. bacteria)
How many bits in a byte?
8 bits are in a byte
How many bytes are in a pixel?
A pixel = 1 byte
What is a pixel?
a sample of light based in that particular position
How many different combinations are there of 0 and 1 in a single byte?
256
An image is a sequence of numbers ranging between 0 and _____
255 (not 256 because we start at 0)
How many bytes does a greyscale image of size 800x600 occupy on the computer?
800x600= 480000 Bytes (480kB)
Because 1 pixel= 1 byte so an image of size MxN pixels occupies M x N Bytes
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?
2^16 = 65536 different values of grey
How many Bytes does an RGB image of size 800x600 occupy on the computer?
800 x 600 x 3 = 1,440,000 Bytes (1.44 MB)
To get MB divide by 1 million
What three colours are used in colour images?
Red, Green, Blue
Image formation means?
Object in, image out (on computer)
Image processing means?
Image in, image out
Image analysis means?
Image in, features out (for example, area and perimeter)
Computer graphics means?
Numbers in, image out
Computer vision means?
Image in, interpretation out
Visualisation means?
Image in, representation out
What does the operation ‘image processing’ do?
1) Enhancement and restoration
2) segmentation (thresholding and edge detection)
What does the operation ‘image analysis’ do?
Feature extraction and measuring
Define binary image
A digital image that had only two possible values for each pixel
Define image segmentation
The process of partitioning a digital image into multiple segments
What is the goal of image segmentation?
To simplify/change the representation of an image into something simpler and easier to analyse
Define image processing
The analysis and manipulation of a digitised image, especially in order to improve its quality
Define image analysis
the extraction of meaningful information from images
List some applications of image analysis (not necessarily biological)
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)
What does dilation do?
Adds pixels to the edges of objects in a binary image
What does erosion do?
Removes pixels form the edges of objects in a binary image
What does watershed do?
Watershed segmentation is a way of automatically separating or cutting apart particles that touch
What is a computer program?
A program is simply a sequence of instructions telling a computer what to do
What is morphological filtering?
It is used to clean an image after segmenting it (it fills in holes, removes isolated background and foreground pixels etc)
What does connected components labelling do?
It allows you to connect together pixels that belong to the same object
Name two ways in which a high-level language can be translated into machine language which the computer can execute
You can either compile or interpret the language
What does binarisation do?
It converts an image into black and white (background black, foreground white)
Define grey level (or grey scale) image
A monochrome image in which pixels typically represent brightness values ranging from 0 to 255.
Define restoration
Given a noisy sample of some true data, the goal of restoration is to recover the best possible estimate of the original true data.
Define saturation
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.
Define thresholding
Thresholding is the quantization of an image into two values. One example is the conversion of a greyscale image to a binary image.
