All Questions
Tagged with image-processing image-processing
3,213 questions
4
votes
2
answers
103
views
Fingerprint enhancement lighter version
I've been advised to ask here, I hope that it fits.
Original question:
I want to create a more straightforward and lighter version of this fantastic repo (which itself is based on Fingerprint Image ...
- 15
2
votes
1
answer
161
views
Feature selection of Gabor filter
I am working with Gabor filter with level set method as in A Level-Set and Gabor-based Active Contour Algorithm for Segmenting Textured Images. As you known, Gabor filter gave many filter output. Some ...
CommunityBot
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1
vote
1
answer
21
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Reducing ringing artifacts during numerical differentiation of depth image
I need to obtain a normal map from dense depth image. Naive differentiation results in serious ringing artifacts near the sharp edges. I have tried using a Sobel filter instead, but it does not really ...
0
votes
0
answers
15
views
Variation of phase due to changes in features in the spatial domain
Let say there is a white ball at the center of a black background in a image. And i move that ball to (x,y) position. So what changes will that cause in phase and by how much. And since phase has a ...
0
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0
answers
21
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Finding the gradient direction from a derivative image
I am working on a task with reconstructing an image from its derivative image on only one direction.
Currently I managed to do this on a derivative image which was taken on X direction, by integrating ...
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0
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0
answers
23
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Gaussian blur with variable standard deviation
I'm trying to find fast ways to evaluate the following integral defined over points $\mathbf{x} \in \mathbb{R}^2$:
$$\Phi(\mathbf{x}) = \frac{1}{2\pi\sigma^2(\mathbf{x})}\int d^2y\, \exp\left(-\frac{|\...
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2
votes
1
answer
304
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Image Segmentation based on coordinates from reference points
I have a set of colors in a card, as below (I can modify the card as required)
I have 4 reference points at four corners. I have a bunch of colors at known coordinates (in mm) from these reference ...
CommunityBot
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1
vote
1
answer
82
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On Human (Face) Detection
There are many face detection and recognition algorithms and APIs out there; however, most of them can produce same results for paintings and avatars as for human face. So, is there any specific ...
CommunityBot
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2
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1
answer
104
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Is signal processing used in block matching algorithms
I'm working on a custom video codec which uses the standard mean squared error to find blocks.
As explained by this youtube video you choose a search area size to find a block in. Each pixel of the ...
CommunityBot
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1
vote
1
answer
36
views
What are different methods to track a moving object with stationary monocular camera
I am new to computer vision and trying to learn object tracking using vision. I read different books on vision where object tracking is discussed. Most of the books mention following two methods: 2d-...
CommunityBot
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3
votes
1
answer
104
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Position vector of Lukas-Kanade optical flow algorithm
The classical optical flow equation by Lukas-Kanade can be simplified as follow:
$$
\frac{\delta I}{\delta x}\triangle x+\frac{\delta I}{\delta y}\triangle y + \frac{\delta I}{\delta t}\triangle t=0
$$...
CommunityBot
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5
votes
1
answer
397
views
Combining two Images with Different Resolutions into Higher Resolution Image
I am attempting to combine two radar images, each of which is a 3-dimensional cube with a range dimension, an azimuth angle dimension, and an elevation angle dimension. One image has high azimuth ...
CommunityBot
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3
votes
1
answer
98
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How to Generate the Kinect Images
What filters are used to get an image like one on the left? I need to find the body pose of a person in a picture.
CommunityBot
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6
votes
1
answer
238
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Discrete Cosine Transform (DCT) as the Limit of Principal Component Analysis (PCA)
On the Wikipedia article about Discrete cosine transform it is said:
For strongly correlated Markov processes, the DCT can approach the compaction efficiency of the Karhunen-Loève transform (which is ...
- 20.5k
3
votes
1
answer
127
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Implementation of Normalized Cut (Spectral Clustering) for Image Segmentation
I have implemented "normalized cut" segmentation. The change here is that, instead of giving an image as input, I have given an matrix of image. As my output looks odd to me. I need to know whether my ...
CommunityBot
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0
votes
1
answer
1k
views
HOG descriptor algorithm
I would like to implement a HOG descriptor in C++.
I found an implementation of this code in Open Pattern Recognition Project - Histograms of Oriented Gradients (HOG) Feature Extraction.
An extract of ...
CommunityBot
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1
vote
1
answer
99
views
Removing the Dot-Patterns Like Noise
I am dealing with an image restoration problem with noisy measurement. I use the classical total variation norm to remove the noise, specifically, the TV-$L_2$ problem. I used the famous Lena image ...
CommunityBot
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0
votes
1
answer
322
views
State of the art in Cancer tumour detection using Digital image processing algorithms
I am trying to understand how image processing is applied for detection of cancer tumor using image processing. Towards this direction I am trying to get latest information i.e state of the art in ...
CommunityBot
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1
vote
1
answer
848
views
How do I get various peak values from a 2-D array or a matrix?
I'm working on 2D array analysis or an image analysis and get to know the different block of peak values marked "circle" in attached plot [e.g. 2*2 matrix] of the 2D array [as shown in Fig. ...
CommunityBot
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2
votes
2
answers
78
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Distinguishing between intensity image plots
I have a series of intensity images generated by varying different scatterer geometries. An example of variation observed by varying the aspect ratio of these geometries is shown below in the three ...
CommunityBot
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5
votes
1
answer
269
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How to Solve ADMM for Total Variation (TV) Minimization Problem For Different Sizes $A$ and $x$ in $Ax=b$
I have matrix $A$ that is $(M \times M)$ square matrix, $x$ $(M \times N)$ matrix, $b$ is $(M \times N)$ matrix. Knowing $A$ and $b$ I would like to get the $x$ from the equation $Ax=b$. $N=p \times q$...
CommunityBot
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1
vote
1
answer
30
views
Detect Largest connected component in a scatter plot (on bivariate data)
I have bivariate data representing the position of an identified reference point along a y axis which ranges from -100 to 100 mm. When I plot this data in a scatter plot I can see outliers and groups ...
CommunityBot
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3
votes
1
answer
80
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Robustness of Horn Schunck Optic Flow Algorithm
Can somebody explain to me why the Horn and Schunck algorithm (probably mostly the smoothness constraint) is robust to image sequences that are quantized rather coarsely in space and/or time. (Thought ...
CommunityBot
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1
vote
1
answer
50
views
Horn Schnuck Optical Flow Algorithm's Formula
In the below pic, I can not understand what U vector is? It says flow field but I can not imagie what really is the flow field?
CommunityBot
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1
vote
1
answer
216
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Segmenting dark spots from a light background?
I need to perform automatic segmentation of dark blue spots on light yellow paper. Here's a very simple example:
In this case, a simple threshold based on hue or brightness works well. But here are ...
CommunityBot
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1
vote
1
answer
86
views
Minimum number of patches needed to find color correction matrix (CCM)
The chart should have at least 9 distinct color patches for 3×3 CCMs (which are generally recommended). Excellent results can usually be achieved with the inexpensive, widely-available 24-patch X-Rite ...
CommunityBot
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4
votes
1
answer
178
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Interpreting results of Sobel Edge Detection
I am implementing A No-Reference Perceptual Blur Metric paper.
Somewhere in the prep steps they mention the use of vertical Sobel filter for finding vertical edges.
The algorithm is summarized in Fig....
CommunityBot
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2
votes
1
answer
519
views
How to compute second order derivative of image using the integral image and box filters?
I want to speed up my blob detection function by computing the second order derivatives of the input image using the integral image and some box filters.
Initially, I used the following method, which ...
CommunityBot
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3
votes
1
answer
131
views
How to find sharpness of an image?
I have a rather difficult image processing image. I would like to rank order a set of images I have by their sharpness. The issue is the images themselves are not of the exact same thing. Usual ...
CommunityBot
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1
vote
1
answer
86
views
Locate No Signal Area Between 2 Signals
I have many datasets which all looks roughly like this:
All the datasets have this in common. First there is an artifact around 0 with an unknown (but likely very high) intensity. Then there is some ...
CommunityBot
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3
votes
1
answer
114
views
Computer Vision: What is a good approach to find the similarity between 2 screenshots of a screen from a mobile application?
I am trying to find an algorithm to determine the similarity between 2 screenshots of the same screen of a mobile application. I have tried structural similarity index, Peak signal-to-noise ratio and ...
CommunityBot
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4
votes
1
answer
238
views
Perceptually Corresponding Error Map
Is there any better measurement of error between two images than just taking pixel value differences?
The problem I am tackling is stitching images containing "sensitive" objects, such as moving ...
CommunityBot
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3
votes
1
answer
261
views
Region growing Vs Clustering
In image processing, how do region growing and clustering differ from each other? There are many papers like clustering based on region growing. I couldn't able to draw a fine line between these two ...
CommunityBot
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4
votes
1
answer
116
views
blur PSF modeling for small stright camera movement
I am interested in reovering images affected by blur of known orientation and known span.
Camera movement during capture is very small, blur span is of about 0-4px.
What is the most accurate way to ...
CommunityBot
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2
votes
1
answer
59
views
Need to understand how wavelet is applied on Image matrix?
i want to understand ,how to find out Discrete wavelet transform of image 4 by 4 size using Haar wavelet on paper ?
CommunityBot
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1
vote
1
answer
225
views
How to categorize the images based on Illumination / shadow?
Input: Cropped face or Non Cropped face images.
Detailed explanation: My project is face authentication. I am using OpenCV face detector to crop face from images. I am using OpenCV implementation of ...
CommunityBot
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1
vote
1
answer
240
views
Analysing 3D image FFT
I'm looking for a way to visually inspect the amplitude of frequency components in a 3D image that I have taken the fftn of in matlab. Does anyone have any idea how to go about this?
CommunityBot
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3
votes
1
answer
3k
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Eye Blink Detection Using Computer Vision
I am working on a eye blink detection project in Matlab. By this moment I have been successfully extracted the images of pupil of eye from the real time video captured via a web cam.
But I am stuck ...
CommunityBot
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1
vote
1
answer
145
views
Improve Alpha Matting on Hair of Human Portrait
I have an image like this:
I am trying to build a semantic segmentation and matting model which currently gives an output like this:
One can see that some regions between the hair strands are fuzzy....
CommunityBot
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1
vote
1
answer
1k
views
PSNR and SSIM on non-rectangular image regions
My goal is to compare the quality of an image with its low-resolution versions using an object quality metric like PSNR. Since such metrics can only be applied on same-sized images, I first upscale ...
CommunityBot
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1
vote
1
answer
5k
views
How to make a contour smooth in OpenCV
I am using OpenCV(4.5.1) and trying to extract a smooth contour of an object on my image.
Firstly I got the contour by:
...
CommunityBot
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3
votes
1
answer
7k
views
Find branches in skeleton image using matlab
I have a skeleton image. I am able to detect branchpoints, endpoints and able to label image using BWMorph, BWLabel. Now I want to differntiate between skeleton center line and branches. In short I ...
CommunityBot
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3
votes
1
answer
86
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Simple Binary Image Classification (Person / No Person) in `C`
i have to do a project for university which is basically to program a tool to classify small greyscale images like those below into person or non-person, in C.
The project is scheduled for around ...
CommunityBot
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1
vote
1
answer
349
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How to obtain the relative position (coordinates) of SIFT feature from image center coordinates?
I have extracted SIFT features (keypoints and descriptors) of training set and saved in an inverted index form.
My question is how can I calculate the coordinates of each visual features in an image ...
CommunityBot
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4
votes
1
answer
4k
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Image Super Resolution Algorithm with Wavelets in MATLAB
I'm trying to implement a simple Image super resolution algorithm (DWT-Based Resolution Enhancement
) in the following paper
Discrete Wavelet Transform-Based Satellite Image Resolution Enhancement
I ...
CommunityBot
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3
votes
1
answer
262
views
How to Find Performance Ratio (PR)?
If we have one image from BSD (The Berkeley Segmentation Dataset and Benchmark) and for this images Ground truth, how to calculate PR?
PR is the ratio of true to false edges, and can be calculated by ...
CommunityBot
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0
votes
1
answer
564
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What distance metric can I use for comparing image features in a nearest neighbour algorithm?
I use Nearest Neighbour function of Scikit learn module in python for training and compare an image set (https://docs.google.com/file/d/0B6zJ3_hrkW40U182SWNWX3o4dE0/edit?usp=sharing&pli=1)
By ...
CommunityBot
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4
votes
1
answer
240
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Regularized Least Squares by Laplacian Operator - Optimal Value of the Regularization Factor (Lagrangian Multiplier)
Consider the cost function
$$f(X,\lambda) = \|AX-b\|_2^2 + \alpha \|LX\|_2^2$$
$A:$Measurement matrix($R_{m\times n}$,$m \ll n$), $b:$observation vector($R_m$), $L:$Laplacian operator($R_{n \times n}...
CommunityBot
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5
votes
1
answer
168
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What are Local and Global Inpainting Techniques in Image Processing?
Is Diffusion-based inpaiting Local or Global?
Is Pixel-based inpaiting Local or Global?
Is Patch-based inpaiting Local or Global?
Can Local-diffusion be used inside Patch-based in-painting problems of ...
CommunityBot
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4
votes
1
answer
1k
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The Kernel of the Guided Image Filter
I am trying to understand how to calculate kernel matrix for guided image filter. Following is the formula for kernel calculation.
where k is window withing pixels i and j belong i assumed that ...
CommunityBot
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