Digital Imaging Concepts Overview

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Questions and Answers

What is the highest resolution commonly used for printing book pages?

75 dpi

133 dpi

2400 dpi (correct)

175 dpi

Which bit-depth corresponds to 16 intensity levels?

8 bits

2 bits

4 bits (correct)

1 bit

What causes false contouring in digital images?

High spatial resolution with low intensity levels.

Using a resolution lower than 75 dpi.

Using too many intensity levels.

Using insufficient gray levels in smooth areas. (correct)

Which of the following is a true statement about intensity resolution?

Intensity resolution is commonly given in bits used to store each level. Signup and view all the answers

What is the range of intensity levels for an image with 8 bits of intensity resolution?

0 to 255 Signup and view all the answers

At which intensity level does false contouring generally become visible?

16 levels Signup and view all the answers

Why is 32-bit intensity quantization considered rare?

Most applications do not require that level of detail. Signup and view all the answers

Which print medium has the lowest resolution among the options listed?

Newspapers Signup and view all the answers

What process is referred to as quantization in digital imaging?

Digitalizing the amplitude values. Signup and view all the answers

What is the relationship between M, N, and the pixel in a digital image?

M rows and N columns form the matrix of pixel intersections. Signup and view all the answers

Which statement correctly describes the intensity resolution of a digital image?

It is the number of discrete intensity levels that an image can represent. Signup and view all the answers

What is the significance of L in image digitization?

It is the integer representing the number of intensity levels. Signup and view all the answers

How is the pixel value at coordinates (m,n) defined in digital imaging?

By the function f(m,n) which can be a function of various other factors. Signup and view all the answers

What condition must L satisfy for an image to be correctly represented digitally?

L must be an integer power of two. Signup and view all the answers

An image with 256 intensity levels is classified as what type of image?

8-bit image. Signup and view all the answers

What is a requirement for two regions to be considered adjacent?

Their union must form a connected set. Signup and view all the answers

In an image where V={1}, what defines if two regions R1 and R2 are adjacent when considering the 4-path rule?

They must have a direct connection through a pixel. Signup and view all the answers

Which distance metric is defined as the sum of the absolute differences of the pixel coordinates?

City-block distance Signup and view all the answers

What condition must be met for a subset S to be classified as a connected set?

There must be a path connecting any two points in S. Signup and view all the answers

When using 8-adjacency, what distinction is made about the boundaries of the 1-valued regions?

The outer boundary forms a closed path. Signup and view all the answers

What characterizes the function f(x,y) in an image formation model?

It represents the intensity of the image at coordinates (x,y). Signup and view all the answers

What do the variables i(x,y) and r(x,y) represent in the image formation model?

i(x,y) is illumination, and r(x,y) is reflectance. Signup and view all the answers

What is the range of values for the reflectance function r(x,y)?

It ranges from 0 to 1. Signup and view all the answers

What does the intensity of a monochrome image correspond to at any point (x,y)?

The gray level, represented as I = f(x,y). Signup and view all the answers

How is the interval for gray levels modified in common practice?

It is shifted to the interval [0, 1]. Signup and view all the answers

What physical process generates the values in the function f(x,y)?

Energy radiated by physical sources like electromagnetic waves. Signup and view all the answers

What is the maximum possible intensity level that can be achieved in an image according to the image formation model?

1 or C, where C represents a bright tone. Signup and view all the answers

In the context of digital images, what is meant by the term 'intensity scale'?

The interval representing all possible gray levels. Signup and view all the answers

What points are considered the 8-neighbors of pixel P(x,y)?

(x-1, y+1), (x, y-1), (x+1, y-1), (x+1, y+1) Signup and view all the answers

How is 4-adjacency defined for two pixels?

Two pixels are 4-adjacent if they are in the set N₄ of each other. Signup and view all the answers

Which of the following describes m-adjacency?

Two pixels are m-adjacent if they are either 4-adjacent or do not overlap in N₄ values. Signup and view all the answers

Given the set V = {1}, which pixel configuration could represent 8-adjacency?

Three rows of pixels where one pixel in the middle is surrounded. Signup and view all the answers

What does a connected component consist of?

All pixels connected directly to a specific pixel. Signup and view all the answers

In an image with pixels having values in the range [0, 255], what can set V typically include?

Any subset of the full range from 0 to 255. Signup and view all the answers

Identify how ambiguity in 8-adjacency is resolved using m-adjacency.

By checking overlap between two diverse adjacent sets of pixels. Signup and view all the answers

What defines 8-path connectivity between two pixels in an adjacency context?

A sequence of 8-adjacent pixels leading from one to the other. Signup and view all the answers

Study Notes

Image Formation Model

An image is represented by a 2D function f(x,y) where the value at coordinates (x,y) represents the energy emitted from a physical source.
The function f(x,y) is composed of two components:
- Illumination (i(x,y)) - the amount of light incident on the scene.
- Reflectance (r(x,y)) - the amount of light reflected back by objects in the scene.
The gray level (I) at a point in a monochrome image is the intensity at that point.
The intensity scale ranges from Lmin to Lmax which are usually shifted to the interval [0,1] or [0,C].
- Lmin= i(min) * r(min)
- Lmax= i(max) * r(max)

Sampling and Quantization

Digitizing an image involves converting the image into discrete quantities.
This involves sampling and quantization.
Sampling is dividing the continuous image into a grid of M rows and N columns.
Each point on the grid is called a pixel.

Digital Image Definition

A digital image is a 2D discrete space representation of an analog image.
The image is represented by a matrix with values f(m,n) for each pixel.
The number (L) of discrete intensity levels must be an integer power of two (2^k, where k is an integer).
Images are often described in terms of their bit depth, which is the number of bits used to store each intensity level.

Understanding Spatial and Intensity Resolution

Spatial resolution refers to the number of pixels in an image.
Intensity resolution refers to the number of discernible gray levels in an image.
Increasing spatial resolution allows for more detail to be captured in an image.
Increasing intensity resolution allows for finer detail to be captured in the range of gray levels.

False Contouring

False contouring is an artifact that can occur when reducing the number of intensity levels while keeping spatial resolution constant.
It appears as distinct lines or bands in smooth areas of an image.

Neighbourhoods of a Pixel

The 4-neighbors of a pixel p are the pixels directly above, below, to the left, and to the right of p.
The 8-neighbors of a pixel p are the 4-neighbors of p, as well as the pixels diagonally adjacent to p.
The m-neighbors of a pixel p are the 4-neighbors of p, along with the diagonal neighbors that share no 4-neighbors with value V.

Adjacency and Connected Components

Adjacency is used to define relationships between pixels in an image.
Two pixels are 4-adjacent if they share a common edge, 8-adjacent if they share a common edge or a common corner, and m-adjacent if they are 4-adjacent or 8-adjacent and the shared corners do not contain pixels with value V.
A connected component is a set of pixels that are connected to each other.
A region is a connected set of pixels.
Two regions are adjacent if their union forms a connected set.
Regions that are not adjacent are disjoint.

Distance Metrics

Distance metrics are used to calculate the distance between two points.
Common distance metrics include:
- Euclidean distance
- City-block distance
- Chessboard distance

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Description

Explore the fundamental concepts of digital imaging, including image formation models, sampling, and quantization. Understand how illumination and reflectance play a role in creating monochrome images. This quiz will test your knowledge on the essential aspects of how digital images are represented and processed.