Test 1 Flashcards
What is an invariant feature
Values remain unchanged under specific transformations (e.g., rotation, scaling)
What is a covariant feature
Values change predictably under transformations (e.g., scaling affects area proportionally)
What is a global feature
Describes an entire image (e.g. colour histogram)
What is a local feature
Applies to individual image regions (e.g., corners, edges, etc.)
Define a feature
A distinctive attribute or description used to label or differentiate objects in images
What is the difference between detection and description in image processing
Detection: Finding features
Description: Quantifying features
True or False: The purpose of preprocessing techniques is to prepare images for further analysis by reducing noise, enhancing features, and normalizing data
True
What is boundary analysis
Focuses on the edges or outlines of objects, aids in object shape identification
What is region analysis
Focuses on the areas or segments within an image, supports texture and pattern recognition
What is boundary following or boundary tracing
It identifies and follows the boundary of an object in a binary image
What are the necessary inputs for boundary following and what is the output
Inputs/Requirements:
- Binary image padded with a border of 0’s
- Single connected region (can be extended to multiple regions)
Output: An ordered sequence of boundary points
Define chain codes
Represent the boundary of an object as a sequence of connected line segments. These segments are described using directional numbers based on connectivity
What are the connectivity types of chain codes
4-connectivity: Segments connect pixels in horizontal and vertical directions (up, down, left, right)
8-connectivity: Segments connect pixels in diagonal directions as well, enabling finer boundary representation
What is a Freeman chain code
A chain code that assigns a directional number (e.g., 0 for right, 1 for top-right, etc.) to each segment between consecutive boundary pixels. An example could look like 0766666453321212 (8-connectivity system)
True or False: Fine-grained grids can result in longer chains that may be more accurate, but could also be more susceptible to noise or segmentation errors
True
Define slope chain codes (SCCs)
An alternative to Freeman chain codes. Uses slope changes between contiguous line segments to represent a boundary
Define boundary approximations using minimum-perimeter polygons (MPP)
A boundary approximation that uses polygons minimizes the total perimeter while maintaining the shape’s integrity
