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18 votes

Why color is coded with two numbers rather than one?

Note: also check out the comments for more pointers. I'll assume that you think of wavelengths, or hue and saturation, which is why you think you could maybe represent color as a single value. You ...
Christoph Rackwitz's user avatar
14 votes
Accepted

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

If I understand your method 1 correctly, with it, if you used a circularly symmetrical region and did the rotation about the center of the region, you would eliminate the region's dependency on the ...
Olli Niemitalo's user avatar
13 votes

Is deep learning killing image processing/computer vision?

Today we had a discussion with a friend of mine. It was a rainy day here in Munich, while a large portion of Europe was having a kind of sunny atmosphere. People were sharing photographs in social ...
Tolga Birdal's user avatar
  • 5,465
10 votes
Accepted

When is a network called end-to-end training?

From feature extraction to learning the desired result, deep learning algorithms can act as full pipelines for solving tasks at hand. End-to-end learning usually refers to omitting any hand-crafted ...
Tolga Birdal's user avatar
  • 5,465
9 votes

Best way of segmenting veins in leaves?

Following on from the above excellent answer, here is how to do it in python using scikit funcitons. ...
Matthew Shun-Shin's user avatar
9 votes
Accepted

How to calculate particles sizes for spheric particles with overlapping and superposition? (Example image included)

Here is what I experimented with: Use ELSD to generate elliptic contours. You could basically use any edge detector, but since in the following stages I will benefit from circle detectors, it is good ...
Tolga Birdal's user avatar
  • 5,465
9 votes
Accepted

Image processing vs Computer vision?

Digital image processing is an extension of digital signal processing and linear system theory into two dimensional signals. Image processing involves all low level tasks such as filter design and ...
Fat32's user avatar
  • 28.3k
8 votes

Difference between optical flow field and motion field?

well, have you ever seen a rotating barber's poll? It looks like the stripes are moving up (optical flow), but of course the motion of the thing is a rotation in the horizontal plane. The rationale ...
Marcus Müller's user avatar
7 votes

Can deep neural networks achieve real-time video analysis?

Nvidia seems to have published some white papers comparing DNN inference performance between high-powered CPUs and (of course) Nvidia GPUs. (one example) Ballpark seems to be that some systems can ...
hotpaw2's user avatar
  • 35.4k
6 votes

Is deep learning killing image processing/computer vision?

Data engineering is still used in machine learning to preprocess and select the data fed to DNNs to improve their learning time and their evaluation efficiency. Image processing (the stuff between ...
hotpaw2's user avatar
  • 35.4k
6 votes
Accepted

Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

It is because in the case of fundamental matrix, each correspondence point relates to only one constraint(i.e it maps a point to a line in other image). Hence 8 correspondence points are required. ...
harshkn's user avatar
  • 241
6 votes
Accepted

Palm Pilot Graffiti

If you are looking for a good explanation of some of the methods used in projects like GRAIL look here: Back to the Future of Hand Writing Recognition
FallenNode's user avatar
6 votes

Is there a penis-detection demo similar to face-detection?

Is there a script / tutorial / demo for penis detection? [...] Fairly serious quesion, future of internet memes is at stake Yes, there is. Common Pattern Recognition techniques will be able to spot ...
A_A's user avatar
  • 10.7k
6 votes
Accepted

Number of dimensions? Color image vs gray scale image? Colour video vs gray scale video? Especially in the context of MATLAB

Color images are usually modeled as a vector valued function of 2D: $$ I : \mathbb{R}^{2} \to \mathbb{R}^{3} $$ Namely for 2D coordinates input it outputs 3 values (RGB). Hence images are 2D functions....
Royi's user avatar
  • 19.7k
6 votes
Accepted

Universal Bases (Dictionary) for Image Compression

This is a great and interesting question. There are 2 ways to look at it, empirically and analytically. But before we start, a major detail is that when dealing with images we mainly talk about the ...
Royi's user avatar
  • 19.7k
6 votes

Why color is coded with two numbers rather than one?

Color spaces are represented by three numbers (not two). That's a direct consequences of the human visual system. Humans have three different type of color receptors in their eyes. Their spectral ...
Hilmar's user avatar
  • 45.4k
6 votes
Accepted

How do I estimate the pose of a camera looking at a flat horizontal surface?

Your problem is called pose estimation. The OpenCV function is called solvePnP(). Be aware that the intrinsic camera matrix must be known in advance. If you don't ...
Rainer P.'s user avatar
  • 531
5 votes

Is deep learning killing image processing/computer vision?

A thorough understanding of signal processing (along with linear algebra, vector calculus, mathematical statistics etc.) is imo indispensable for non-trivial work in the field of deep learning, ...
AruniRC's user avatar
  • 180
5 votes

Removing Noise from Dental Radiography

As far as I understood, by image derivation you mean extracting edges. I would recommend to filter the image by a relatively large Gaussian filter. If computational cost of image derivation is ...
MimSaad's user avatar
  • 1,976
5 votes
Accepted

Detect circles in image

1) Normalize your image to range $[0,255]$. 2) Select a threshold and threshold the image. For your image, what worked is: $\tau=[140-150]$. 3) Compute a Euclidean distance transform. 4) Apply ...
Tolga Birdal's user avatar
  • 5,465
5 votes

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

Rather performance intensive, but should get you accuracy as wanted: Edge detect the image Hough transform to a space where you have enough pixels for the wanted accuracy. Because there are enough ...
Rob Audenaerde's user avatar
5 votes

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

There is a similar DSP trick here, but I don't remember the details exactly. I read about it somewhere, some while ago. It has to do with figuring out fabric pattern matches regardless of the ...
Cedron Dawg's user avatar
  • 7,570
5 votes

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

This is a go at the first suggested extension of my previous answer. Ideal circularly symmetric band-limiting filters We construct an orthogonal bank of four filters bandlimited to inside a circle ...
Olli Niemitalo's user avatar
5 votes

Fundamental matrix rank

This is not a proof, but maybe an intuition why this conjecture can be true for the points in general position. From the properties of rank we know that: $$ \mathrm{rank}(F) = \mathrm{rank}(F^\top) = ...
Tolga Birdal's user avatar
  • 5,465
5 votes
Accepted

Importance of Phase in FFT of an image

The amplitude of an image represents the intensity of the different frequencies in the image. Therefore, it holds the geometrical structure of features in the image (i.e. changes in the spatial domain)...
Nitzan's user avatar
  • 109
5 votes

Universal Bases (Dictionary) for Image Compression

As a complement to the neat answer by @Royi, I would add that "sparsity" is originally a heuristic principle in science, that applies well to many interesting really world data and problems. ...
Laurent Duval's user avatar
5 votes

How do I estimate the pose of a camera looking at a flat horizontal surface?

All of this is written assuming that you have already calibrated the camera for its intrinsic matrix. If you have not done this, then you need to do so beforehand, or you need to look to the answer ...
TimWescott's user avatar
  • 12.8k
4 votes

Why do we use the HSV colour space so often in vision and image processing?

As others mentioned, it is beneficial to separate the luma from the chroma. The luma varies greatly in the scene based on the amount of light falling on the object. Chroma, on the other hand, ...
ybungalobill's user avatar
4 votes

ORB Algorithm: What Is Intensity Centroid?

Because wo want to get the centroid of the image(a block/patch) by the intensity. m00:p = q = 0,sum the intensity matrix. m10:p =1,q = 0,sum of the x-direction. m01:p = 0,q = 1,sum of the y-direction. ...
LingJun's user avatar
  • 41

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