Digital Imaging Concepts Overview

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

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.