19
votes
What is the difference between object detection, semantic segmentation and localization?
I read a lot of papers about, Object Detection, Object Recognition, Object Segmentation, Image Segmentation and Semantic Image Segmentation and here's my conclusions which could be not true:
Object ...
- 291
15
votes
How to generate stereo image pair from a stationary mono camera?
You can't. You have video of the scene from a single vantage point. Without depth information, you can't infer what the scene would look like from another vantage point.
D.W.♦
- 156k
11
votes
What is the difference between object detection, semantic segmentation and localization?
Since this issue is still not quite clear even now in 2019, and it might help new ML-Learners choose,
here is a very good image showing the differences:
(localisation is the bounding box around the "...
- 211
9
votes
How to generate stereo image pair from a stationary mono camera?
The terms you probably want to google for are "inferring depth maps". Just like your brain tricks you into seeing 3d if you close one of your eyes, you can heuristically recover depth maps from single ...
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7
votes
Google DeepDream Elaborated
The idea of DeepDream is this: pick some layer from the network (usually a convolutional layer), pass the starting image through the network to extract features at the chosen layer, set the gradient ...
- 640
7
votes
Accepted
Computer Vision - What is spatial histogram/pyramid feature?
Spatial histogram. A simple histogram is obtained by taking a region of an image, assigning a label to each pixel (somehow; via some mapping function), and then computing a histogram of the labels. ...
D.W.♦
- 156k
6
votes
Computer vision: Why do random filters perform similar to edge detectors?
Intuition, for a small case
Why? Let's look at the simplest possible case, where the kernel is 1x2 (i.e., two pixels wide and one pixel high).
Here's a kernel matrix for an edge detector that ...
D.W.♦
- 156k
6
votes
Convert HSV to RGB colors
This is my first post on StackExchange! I realize it's on a fairly old post but perhaps someone else will appreciate an explanation!
I will preface this by saying that I come from a background in ...
- 61
5
votes
Accepted
How can I sum pixel values over a rotated rectangle?
One simple technique that's probably not optimal, but is better than naively enumerating all pixels in the rotated rectangle, is to use "integral columns" (thanks to Yves Daoust for the name):
...
D.W.♦
- 156k
5
votes
What is the difference between the fundamental matrix and the essential matrix?
I want to add one thing to @Dima's answer, just so things are absolutely clear:
$E = (K')^TFK$ (note the transpose)
You can see how this also captures that the fundamental matrix takes image ...
- 51
5
votes
Machine learning: do the benefits of more data plateau after a certain point?
Yes, typically there will be a plateau. There's usually no way to guess exactly where the plateau will be, a priori; the only way to find out is to build larger and larger data sets and see what ...
D.W.♦
- 156k
4
votes
Accepted
What are the vertical and horizontal focal lengths?
Note that they assume a pinhole camera model. The term 'focal length' means something different here than it does with a lens camera.
All you ever really need to know about the pinhole camera model ...
- 186
4
votes
Accepted
What is the point of an active shape model in facial recognition?
The active shape model algorithm is used to locate precisely the eyes, eyebrows, nose and mouth of a person. It is also used to align faces that are tilted.
It is not used directly for face matching ...
- 91
4
votes
Accepted
Computer vision: object detection with labels that are single coordinates
The state of the art in such problems is done these days via deep neural networks. Among others, two popular and recent approaches for solving the problem of detection and localization of objects are ...
- 398
4
votes
Accepted
How is RANSAC used to estimate a homography given the descriptors of both images computed with SIFT?
How do you estimate inliers? You use RANSAC. That's what RANSAC does for you: it computes a homography and gives you a prediction for which pairs are inliers and which are outliers.
In SIFT, we ...
D.W.♦
- 156k
4
votes
Efficiently labelling training data in machine learning
You can't. You can't squeeze blood out of a stone. There's no such thing as a free lunch. You can't get something from nothing. If you want labelled images, you will need to label them yourself, ...
D.W.♦
- 156k
4
votes
Accepted
Difference between Image Analysis and Computer Vision
Maybe the web does not have an answer, but the classical book of Image Processing by Gonzalez and Woods has. I will summarize a part from a chapter that I have read.
There is no clear boundary ...
- 181
3
votes
Accepted
Segmenting a human body point cloud into limbs
Suggestion: for each point $P$ in the point cloud, find which bone it is nearest to, and associate it with that bone. In other words, find which point $Q$ on the skeleton is closest to $P$, and ...
D.W.♦
- 156k
3
votes
What is the difference between object detection, semantic segmentation and localization?
I believe just "localization" means "single object classification + localization using a 2D or 3D bounding box".
"Object detection" is localizing + classifying all instances of known object classes ...
- 131
3
votes
Register images containing objects with varying distance to the cameras
Yes, if there is a lot of variability in the distance to the objects in the scene, then global registration will work poorly.
Let me back and give some background on how global image registration ...
D.W.♦
- 156k
3
votes
Accepted
Is it correct to use the pinhole camera model to get the mapping of a 3D line to a line in an image?
The assumption is correct, if(f) you project the 3d line into the rectified image. The idea of projecting a 3d-line to a pixel-line is most often used in a stereo setup with two cameras: if the left ...
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3
votes
Is it correct to use the pinhole camera model to get the mapping of a 3D line to a line in an image?
Please refer: Perspective Projection and Perspective Projection Matrix.
Essentially pinhole camera is perspective view behind the camera. Since we need to divide the $z$ coordinate at places, we have ...
- 4,807
3
votes
Accepted
Which algorithm for counting the occurrences of a certain pattern (spots) in an image?
The best way to get an orientation is to read a textbook on computer vision or image processing. There are lots of techniques known, and that's often the best way to get an introduction to a broad ...
D.W.♦
- 156k
3
votes
What is 'real time' in a Computer Vision context?
There is no one answer to this question. "Real time" can mean very different things, depending on what kind of sensor or sensors you are using, and what you are trying to do. By the way, editing and ...
- 568
3
votes
What is 'real time' in a Computer Vision context?
In computer science, a real-time computing (RTC) system is one that guarantees a response before a previously set deadline.
For a stream of images, that implies that a real-time system is one that ...
- 886
3
votes
Accepted
Is there a metric for the similarity of two image filters?
The ‘k-translation correlation’ is probably a good candidate for what you are looking for. It measures the maximum correlation between a pair of two filters $\mathbf{W_i}$ and $\mathbf{W_j}...
- 46
3
votes
using orientation sensor data to predict image points
It turns out that I had two bugs that broke my experimental results:
Even though the rotation matrix reports the rotation from Earth to Device, I should have been applying the opposite rotation to ...
- 191
3
votes
Accepted
Given a low resolution video, is it possible to create a higher resolution image
It heavily depends on the setting, accuracy and goal, but shortly, yes, even considering practical application.
Theoretically of course it is possible, with various (or used together) techniques like ...
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