Questions tagged [opencv]
OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision.
356
questions
1
vote
0
answers
91
views
Anti tremor motion detection
I'm programming in c# using opencv (emguCV). I use motion detection approach to detect some changes in a paper wall. For example it's may be colored by a laser pointer. My problem is that when I use ...
- 146
1
vote
1
answer
8k
views
How can I construct a Band-pass filter from a low and a high-pass filter?
Suppose, I need to construct a Band-pass filter in OpenCV. But, I know, there are no functions in OpenCV for Band-pass filters.
Now, what I need to do is to have a low-pass filter and a high-pass ...
user18425
1
vote
0
answers
60
views
How to use Mikolajczyk evaluation for detectors/descriptors?
I want to compare different detectors/descriptors (both binaries and not) for my application and I want to use the Mikolajczyk evaluation framework, which is became a standard in the community about ...
- 111
0
votes
2
answers
946
views
How many types of Bandpass filters are there for image processing?
This article shows that:
Ideal Bandpass filter
Butterworth Bandpass filter
Gaussian Bandpass filter
Is that classification correct?
Are there any other types?
user18425
0
votes
1
answer
804
views
Poster detection in OpenCV?
I'm really new in image processing, so please sorry I'm a newbie. I tried to use the squares.cpp for detecting posters (since they usually are rectangles) without using expensive feature detectors (...
- 111
0
votes
1
answer
186
views
Count the vehicles flow that pass over one bridge
I live in an apartment near a bridge. From my window I can see the cars traveling over the bridge as you can see below:
Is there a relatively simple manner to count each car pass over the bridge? ...
- 113
3
votes
2
answers
6k
views
How to remove noise from this image without causing the crack to 'shrink'?
I am currently embarking on an image processing project to detect cracks on surfaces using OpenCV and Visual Studio via C++. I have tried writing my program and at the moment, I am stuck because I ...
- 31
3
votes
1
answer
261
views
How should calibration points be distributed?
I do camera calibration for a single camera with a chessboard pattern in opencv for the first time.
The focus is fixed.
I'm not sure how to do it, there seems to be many questions:
How many images ...
- 252
0
votes
1
answer
2k
views
Which pattern (circle pattern or checkerboard pattern) should be used for automotive camera calibration (fisheye/wide webcam)?
Calibrating a Fish-eye camera / webcam with large angle mounted on car by using opencv 3
One important issue is to define the calibration pattern and its position !!!!
The affects error that paly an ...
- 3
0
votes
2
answers
4k
views
Object detection in binary image
This task comes from tracking object on a steady background. So far I was able to remove the background and obtain binary masks like this:
I need to get bounding rectangle of the toy without the ...
- 21
0
votes
1
answer
114
views
Finding crosses and their orientation on a given image
I want to recognize table structure from some arbitrary photo image and store it in some formal notation (Let it be HTML table notation).
For example I have this blurry image as input:
After ...
- 101
-1
votes
1
answer
149
views
Add padding to object in 4-channel image
I have a 4-channel image (.png, .tif) like this one:
I am using OpenCV, and I would like to add padding of type BORDER_REFLECT around the flower. ...
- 121
1
vote
0
answers
48
views
Get level of wellness in a cascade classifier using LBP
I'm currently working in a Lolipop LBP cascade detector using OpenCV. The training is correctly done and the cascade classifier detects the sticks of the Lolipops correctly but with some minor errors. ...
2
votes
2
answers
7k
views
Blending artifacts in OpenCV image stitching
I am using OpenCV to blend a set of pre-warped images. As input I have some 4-channel images (*.png or *.tif) from where I can extract a bgr image and an alpha mask with the region related to the ...
- 121
1
vote
2
answers
212
views
Hand Jitter Problem
I am currently developing algorithm using openCV C++ for implementing laser as a mouse.Currently am having an issue of hand jitters.(ie. The presenter's hand may shake unnecessarily which may cause ...
- 111
0
votes
1
answer
3k
views
Can I create a transformation matrix from rotation/translation vectors?
I'm trying to deskew an image that contains an element of known size. Here's a test image:
I can use aruco::estimatePoseBoard which returns rotation and ...
- 101
1
vote
1
answer
3k
views
Improve coverage of BackgroundSubtractorMOG2 and findContours
I'm trying to track players on a soccer field, using a fixed camera. The picture below shows the results of BackgroundSubtractorMOG2, the second picture below the results of findContours on the ...
- 11
3
votes
1
answer
4k
views
NORM_HAMMING2 vs NORM_HAMMING
I'm trying to use ORB features with a cv::BFMatcher. ORB is based on binary descriptors so HAMMING must be the choice, but I'm not sure I understand the difference ...
0
votes
2
answers
4k
views
Should I use CV_HAAR_SCALE_IMAGE while using LBP CascadeClassifier?
I trained a cascade-LBP to detect Lollipops with 1000 images, now I'm trying to "adapt" the openCV HAAR-Cascade example to use my LBP trained .xml but I'm not sure about the "HAAR_SCALE_IMAGE" flag, I ...
2
votes
1
answer
289
views
What is a good way to locate butterfly in an image
I have some images of butterflies. I've downloaded them from here. A sample is below:
In each image, the most prominent object is the butterfly (with flowers, leaf etc in background). I usually go ...
- 141
5
votes
2
answers
61k
views
Python - Normalized cross-correlation to measure similarites in 2 images
I'm trying to measure per-pixel similarities in two images (same array shape and type) using Python.
In many scientific papers (like this one), normalized cross-correlation is used. Here's an image ...
Paul Parneix
4
votes
3
answers
2k
views
Vein extraction from this image
I have this image:
What methods should I use to extract the veins from this image.
Thank you.
- 41
1
vote
1
answer
282
views
Can I segment characters from this image with CSV?
I am trying to segment my characters on this image with using column sum vector.
This method actually works on the paper I've read about license plate recognition.
it looks useful for my images ...
- 257
1
vote
1
answer
676
views
Saliency Map based on itti model
i want to create a Saliency Map based on itti model via OpenCV(Python). what i'm doing is that:
1- first i change image color space from RGB to LAB color space
2- for each color channel, i create a ...
- 143
10
votes
2
answers
2k
views
Log-Polar DFT Based Scale-Invariant Image Registration
I'm trying to do image registration using phase correlation as described in the Reddy Chatterji paper. In my case, the images may be scaled and translated relative to each other.
The algorithm for ...
- 203
0
votes
0
answers
2k
views
How to calculate the scale, rotation angle and translation between 2 images if we know the homography result matrix?result
I got the result of findHomorgraphy in OpenCv. As below:
Homography transform matrix:
[-1.1534205416542787 0.7834287271121142 527.9064589440736
-0.2415444621693116 0.16412191792642924 ...
- 11
3
votes
1
answer
69
views
Getting Composition of a Mixture of Colors
I wanted to validate a thought on blending of colours digitally.
Imagine I have two colours, $C_1$ $(R_1,G_1,B_1)$ and $C_2$ $(R_2,G_2,B_2)$. Now, I create colour $C3$ as follows:
$C_3 = \alpha C_1 + ...
- 133
1
vote
0
answers
1k
views
Why correlation coefficient template matching perfoms better than cross-correlation and square-differences method
I am using this template in OpenCv's match template function by converting all images to grayscale.
Here are my result using sum of square differences,cross correlation and correlation coefficient....
2
votes
3
answers
117
views
Background averaging not working
I'm working on a problem where I'm trying to use background averaging to see what the frame looks like in a beehive behind the bees. I've been trying to use standard averaging (I take an image every 1 ...
- 193
2
votes
0
answers
2k
views
Implementing a 2d butterworth filter for image processing?
I am at the moment trying to implement a bandpass butter worth filter which i then can use to apply on my original image. Problem is though My implementation of it using OpenCV doesn't seem to be ...
- 359
0
votes
2
answers
2k
views
Implementing contraharmonic filter
I am at the moment trying to implement a contra harmonic filter,to remove the pepper noise from an image. But the implementation of it seems a bit incorrect, and I am not sure what is wrong.
...
- 359
1
vote
1
answer
2k
views
Rotated object detection by Viola jones Algorithm
In my project I need to detect rotated and non-rotated faces in real time. I read original articles and try to use common implementation in matlab and openCV. And as I understood Haar features are not ...
3
votes
2
answers
9k
views
How to verify if two images have the same object/content?
I am truly new to computer vision field, but it is fascinating me! I have now a challenge in my hands and I am seeking for mentors/advisers to give me some follow up.
My project is: From a picture of ...
- 131
1
vote
1
answer
597
views
Creating a convolution kernel from filter description
I am not quite sure whether the question I am stating is right, or if I am trying to combine two not related topics but here it comes..
I am trying implement and apply a contra harmonic mean filter, ...
- 359
4
votes
1
answer
2k
views
Image Gradient: Light to Dark, Dark to Light
From link:
Black-to-White transition is taken as Positive slope (it has a
positive value) while White-to-Black transition is taken as a Negative
slope (It has negative value). So when you ...
- 141
5
votes
2
answers
1k
views
What Is the Best Color Space to Work with for Hand Detection: RGB, HSV, or YCrCb?
I'm working on hand gesture recognition using C#. I'm using OPENCV for skin detection but its performance is not optimal. So I decided to do some filtering based on color space, but I do not know what ...
- 151
1
vote
1
answer
185
views
Computer vision, Coupon code detection, sugested algorithms
The telecommunication operator in my country has coupons that used to recharge the balance
I want to develop an Android application, that with the camera can take the scratched number and recognize ...
1
vote
3
answers
1k
views
HDR Imaging - Exposure Compensation
Tried HDR Algorithms of OpenCV. Since the algorithm takes pretty much time. I tried few alternative steps as follows.
Took sample images from: HDR Images
1. Divided the image into four equal regions ...
- 121
0
votes
1
answer
3k
views
Finding Distance between Cameras in Stereo Vision
We know how to create disparity map from stereo vision with OpenCV. My question is How can we find/estimate distance between cameras from two image taken from these cameras in OpenCV?
- 103
6
votes
1
answer
3k
views
How are the scaling parameters included (extracted from) an essential matrix?
An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as:
$$E=K'^TFK$$
where K is the calibration and F ...
user17348
5
votes
1
answer
2k
views
Obtain motion between image features by means of the homography matrix
I have been reading several really good answers about how to obtain camera pose (rotation, translation, etc), such as this one and this one, but I am not sure how this applies to my problem.
My ...
user17348
2
votes
2
answers
1k
views
Understanding this Gabor Filter equation
I am working on a project where I need to implement road edge detection. This research paper suits my requirement in the best way, so I am studying it: http://imagine.enpc.fr/publications/papers/...
- 21
0
votes
0
answers
582
views
how to compute horizontal angle of a pixel from a computer vision camera
My program needs to compute the angle of a pixel from a computer vision camera that has 120 degrees field of view, and resolution of 640 pixels wide and 480 pixels high.
Program receives an X,Y array ...
- 101
1
vote
2
answers
1k
views
texture matching between patches of an image
I have an image A which I have divided into 4 x 4 subband images. For a given patch P1 in ...
- 75
0
votes
1
answer
888
views
2D DWT Image Issue
In the literature, I see that a 2D signal can be transformed by first doing a 1D transformation on each row of the matrix followed by the same procedure on each column. It seems that $k^{th}$ level ...
- 203
4
votes
1
answer
2k
views
Detecting defects/differences in printed images
I've been experimenting with various methods to detect defects in printed images. Features that are qualified as defects may include scratches, discoloration, etc.
I'm not very experienced in image ...
- 163
1
vote
0
answers
1k
views
Opencv circle detection android
Goodmorning,
I have to do a circle detection with android studio using opencv, i follow the example find in internet but it didn't work and i don't understand why, i'm new of android. Can someone help ...
- 11
2
votes
2
answers
3k
views
Detecting water level in an image
I have designed a surface with a shape like a rounded rectangle and I want to detect its exact boundaries in a photo I take from it. A sample photo is like this:
I have tried thresholding the image ...
- 123
0
votes
1
answer
10k
views
Difference between cv::subtract and operator - in cv::Mat OpenCV
What's the difference between cv::subtract and operator - in OpenCV?
Mat original = imread...;
Mat smoothed, difference, result;
smoothed - original image ...
0
votes
1
answer
884
views
Mat and int are incompatible? [closed]
anybody knows what this is?
Mat mat = (Mat_<double>(3, 4) << 0, 0, width, width, 0, height, height, 0, 1, 1, 1, 1);
I dont know what mat would be in ...
- 103