Untitled Deck Flashcards
(35 cards)
How to calculate row based index
row * width + col
How to calculate col based index
col * height + row
In a grey scale image what does a hihg peak in the histogram indicate?
high levels of noise?
where does image noise tend to be in images (in terms of frequency)
high frequency values
what do low frequencies relate to in images
overall structure
What is the purpose of using an image pyramid in a coarse-to-fine template matching strategy?
To initialise matching at coarse scales before refining at finer scales
In least squares line fitting, what parameters are estimated?
Slope and intercept
are parallel lines after an affine warp preserved?
yes
what method is best for outliers or occlusions
RANSAC
what happens to the ratios during an affine transform
They are preserved
what happens to circles during affine transform
they become elipses if scaled non uniformly
The closed‐form least squares solution
β=(X^TX) ^−1 X ^TY
when are lsm params refined
they are refined continuously for sub - pixel result
by how much does pyramid downsample?
2 it halves width and height
how many degrees of freedom does a 2x2 mat have?
8
what are advantages of local feature descriptors
efficiency,extensibilty,robsutness to occlusion,distinctiveness
when is ransac used?
It is used in matching
standard sift has how many dims
128
what does ransac stand for?
random sample consensus
what is hte first step in feature based alignment
Extract keypoints and compute descriptors
In stereo vision, the disparity 𝑑 at pixel coordinate (x,y) is defined as:
The horizontal offset between matching pixels in left and right images
Dynamic programming in scanline stereo primarily enforces which constraint?
DP finds the optimal, non‐crossing match path along the scanline.
In dynamic‐programming stereo, occlusion penalties should be set:
Much larger than a typical match cost, to avoid excessive skipping.
what does sgm do with matching costs?
Aggregates matching costs along multiple one‐dimensional paths.
