# Questions tagged [blur]

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### Gaussian Blur - Standard Deviation, Radius and Kernel Size

I've implemented a gaussian blur fragment shader in GLSL. I understand the main concepts behind all of it: convolution, separation of x and y using linearity, multiple passes to increase radius... I ...
• 393
18k views

### How do I remove motion blur?

Is there a generically accepted method of removing motion blur from an image. For a simple case, we can assume that motion happens in a straight line. I assume that it's a two part process composed of ...
• 5,236
3k views

### Deconvolution - Richardson Lucy vs. Wiener Filter

I am studying some deconvolution techniques, In order to remove motion blur, like: Richardson-Lucy Wiener Are there any pros / cons of using one versus another? For example which are the pros / cons ...
• 305
5k views

### Isolate the non blurred part of foucsed image

I have an image taken by a mobile phone camera with focus on a part of it let say a face or whatever. I want to know -approximately- where is the focused area. For example, a bounding box around the ...
17k views

### How to locally quantify the 'sharpness' of an image?

I am trying to quantify how much sharpness (or acutance) is in a picture which has some bokeh (out of focus background). I am using the Python scikit image for that. Here is my naive approach: ...
• 173
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### Degraded image: Wiener Filter vs Wiener deconvolution

I am studying methods for recovering images (that has been blurred and noised). Can someone explain the difference between: http://en.wikipedia.org/wiki/Wiener_deconvolution http://en.wikipedia.org/...
• 305
15k views

### Gaussian Blur In MATLAB and Connection to Image Resolution

I am calling fspecial() in MATLAB to create a Guassian blur of an image. For example, ...
• 163
862 views

### Deblurring algorithm to precede thresholding - speed over accuracy

I'm writing an app that recognizes Sudoku puzzles from a camera input. I'd like to remove camera blur from the images to improve recognition. Here is an example image: Since I'm processing a ...
• 113
132 views

### The Effect of the Finite Radius of Gaussian Kernel

Page 168 of Digital Image Processing, Global Edition says: we know that the values of a Gaussian function at a distance larger than 3𝜎 from the mean are small enough that they can be ignored. If we ...
11k views

### How to approximate gaussian kernel for image blur

From wiki, a $3 \times3$ gaussian kernel is approximated as: $$\frac{1}{16}\begin{bmatrix}1&2&1\\2&4&2\\1&2&1 \end{bmatrix}.$$ Applying this kernel in an image equals to ...
• 153
516 views

### What Is the Relation Between Deblurring and Deconvolution in Computer Vision and Image Processing?

The deblurring problem can be modelled as follows $$f = \phi u + \epsilon, \; \epsilon \sim N(0, \sigma)$$ where $\phi$ is a filter (e.g. a low-pass filter) and $\epsilon$ is a Gaussian noise. In ...
9k views

### Fastest Available Algorithm to Blur an Image (Low Pass Filter)

I am working with a camera that produces ugly artifacts: by using ANY blur filter on the camera's output the visual quality improves drastically: The above image was created using OpenCV's cv::...
• 145
3k views

### How Does Gaussian Blur Affect Image Variance

I am trying to find a way to analytically estimate how the noise (or variance in pixel values) will be affected for a zero-frequency image of random noise after applying a Gaussian blur. In more ...
• 141
18k views

### How to Calculate Gaussian Kernel for a Small Support Size?

How to calculate the values of Gaussian kernel? I think I understand the principle of it weighting the center pixel as the means, and those around it according to the $\sigma$ but what would each ...
• 41
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### Blurring Non-Uniform Areas

I have an image with arbitrary area (the boundary is shown in gray): I would like to blur just the image within boundaries. Ordinary blur causes the background proliferating to image and vice versa. ...
• 4,255
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### blur detection using opencv

I'm writing a script to detect blur images using OpenCV by applying Laplacian filter and calculate the std but there is a problem the std for images that contain motion blur is very close to those ...
71 views

### Calculate magnitude of the gradient using higher order statistics

I am making a model for detecting blurred part of an image. I'm using features described in the paper Blurred Image Region Detection And Segmentation by Hyukzae Lee and Changick Kim, and I have a ...
379 views

### How to denoise a video stream from poor CCTV lighting

I have grainy CCTV footage that will need some amount of clean up. I request for ideas on the best way to clean out the noise. I am attaching a frame extracted from the video here for hints on the ...
367 views

### Which Blur is being used in this effect

I'm trying to recreate an effect used on photoshop called satin effect, which has an option that control the size of the satin, which I think it's just a special blur applied to the satin pattern So ...
840 views

### Metric for image sharpness?

Suppose I have a blurry image: a photo convolved with a gaussian blur kernel of unknown sigma. I would want to deconvolve the blurry image using several gaussian kernels (with different sigmas). Is ...
• 131
93 views

### What does the $H$ operator exactly do in the deconvolution process and why is it needed?

According to Deblurring Dynamic Scenes via Spatially Varying Recurrent Neural Networks, given a 2D sharp image $x(m, n)$ and a blur kernel $h(k, l)$, the blurred image is obtained as  y(m, n) = (x*h)...
• 401
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### What is the most efficient way to perform Gaussian blurs for varying sizes of Gaussian kernels in an image?

I have detected corner points of images using Harris corner detector in GLSL and now, I intend on using Fast Retina Keypoint(FREAK) as keypoint descriptor to later match the keypoints between images. ...
• 131
733 views

### Why does an image get blurry beyond a limit of zooming?

As we have came cross a phenomenon where a picture get blurry and more blurry as we zoom in a image beyond a limit. Why does it happen?
• 143
90 views

### What is the type of blurring in such an image?

I can't figure out what type of blur such an image has and how I would be able to generate it in python. I would be grateful for any help. I tried Gaussian blur, bokeh blur, Wolf and Born out of focus ...
4k views

### Is It Possible to Reconstruct the Original Image from Laplacian Pyramid?

In our computer vision course, my professor said we can reconstruct the original image from the Laplacian pyramid. It just feels to me that information is lost after doing subsampling and upsampling. ...
• 123
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### Image zoom out using Gaussian blur and downsampling

I am trying to implement a simple zoom out algorithm using two steps: The image is blurred using gaussian convolution of standard deviation $0.8\sqrt{{\tt zoomfactor}^2-1}$ as we saw in class. The ...
• 245
1k views

### Edge map based on a Haar Wavelet Transform

I have been implementing the paper Blur Detection for Digital Images Using Wavelet Transform and was asking myself how the following formula could reconstruct the edges given a Haar Wavelet ...
• 123
117 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 ...
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
7k views

### What is the difference between convolution filter, low-pass filter, and median filter?

Isn't blur filters, like median filter, a type of convolution filter? How does a low-pass filter relate to them? Why does this guy differentiate convolution filters here from blur filters here?
1 vote
1k views

### Gaussian Blur Detection

Let's say you have an original image and a version of the same image that may have been convoluted with a Gaussian blur. How could you demonstrate that the Gaussian blur has been applied and calculate ...
• 113
1 vote
1k views

### Generating Kawase Blur Kernels to Approximate a Gaussian Blur on an Image

Is there an algorithm to generate the Kawase Blur Kernels to approximate the actual Gaussian Blur (of a specific kernel size, and if possible, a sigma)?
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1 vote
3k views

### Measuring sharpness/contrast for autofocus

For the implementation of an auto-focus for the raspberry cam I need some measure of image sharpness. I used the following sample picture: The first approach was to compute the shannon entropy of the ...
• 111
1 vote
28 views

### Compare sharpness at subpixel level

I'm working on algorithms for a camera system (which go down to sub-pixel precision). Until now, I just worked on a recorded dataset, but I'm now moving to real cameras. My question is how to find the ...
• 111
38 views

### Image Processing [closed]

I have an image and I am trying to find its rows and columns. A = imread('lena.jpg'); nrows = size(A,1) ncols = size(A,2) This is 3 dimensional matrix. Output ...