Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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15 views

How would I go about to deconvolve an image acquired by a square detector? (see gif)

So, I acquired some images by scanning a radiation source with a square detector like in the following gif. Where the dashed grid represents reality, the 3x3 square my detector, and the 4x4 my ...
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81 views

Non Linear Remapping of the Pixel Values

Suppose you take a photo of a beautiful scene of mountains and a lake. The representation devotes half of the scale between black and white to the bright surface of the lake, and the other half to the ...
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2answers
269 views

compression algorithm

Steganography can hide one image inside another. If we have a compression algorithm that allows us to fit the bits for two images into the size of one, can we think of a way to modify a run-length ...
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1answer
589 views

What Does It Mean When Cross Correlation Between Two Images Occur at Negative Coordinates

I am using Matlab normxcorr2 to calculate the cross correlation between several images, something like what has been done here: in Matlab documentation. There are some of the examples that I get ...
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9 views

Measure that Compares an Actual Old Document from a Synthetic Old Document

I have collected dirty background images, below is the sample: I have also a collection of an actual image of a dirty document with text on it, just like below: My problem with my actual image of a ...
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1answer
18 views

Find common features across images

Consider multiple images that share a common feature. More specifically, they are the sum of multiple features, and I know that one of those is present in all. What is the best method to extract this ...
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1answer
69 views

What does this notation $g(x) = S\{\delta(t) \}(x)$ mean?

What does this notation mean $g(x) = S\{\delta(t) \}(x)$ mean, where $S$ is a "system", $\delta(t)$ is the impulse function and $g(x)$ the output function of the system? I am really not familiar with ...
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1answer
27 views

Salt and Pepper impulse Denoising opencv

I am creating a generic method to work on salt and pepper noise and variants. The example images are as shown below : I tried few methods, such as ...
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1answer
411 views

how gabor filter is used on image texture edge detection

as I searched gabor filter is most used tool on texture analysis and edge detection in digital image. its said that it searches a certain frequency as a texure around a pixel or point to find the ...
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1answer
820 views

how sobel edge detector as a first order derivative is turned to a 2 dim filter?

I want to know theorem behind sobel operator. basically a first order derivative is -1/2 0 1/2 . its a vector. the question is how this vector is turned to a matrix below and what was theory and ...
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1answer
406 views

Face Recognition: Simplistic Explanation on PCA Eigenface Algorithm

I m working on a project that I have to use eigenface but I have some uncertainty and I dont know how to deal with it. There are some tutorials about it on internet but I can't understand what exactly ...
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1answer
43 views

How Last Edge Image Can Be Achieved from Law Masks

as we know thechnique of law edge detection has 25 2d masks that is obtained form 5 different 1d filters. we can use each of those masks on image with convolution but how can we obtain final result? ...
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257 views

Easy way to get rid of noise in a hand drawing

I would like to take a user's hand drawn input, and filter out "noise", aka small sketches or blobs, where the user might have screwed up and accidentally touched his hand to the drawing device, or ...
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Intelligent lmaging? [closed]

There is a new reasearch field in image processing called as 'intelligent imaging " What is it ? Actually i want to apply for MS in electrical engineering and my target university is offering ...
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729 views

Which Transformation, Or Similarity Metric, Is Rotation, Shift and Scale Invariant?

I have an algorithm to to detect copy-move forgeries in images. I used block matching to detect regions of an image that were forged with copy-move forgery and highlighted the alleged areas. For block ...
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2answers
764 views

How to Match 2 Signals which Are a Shifted and Scaled Version of Each Other

I have 2 signals S1 and S2 that contain the same information, but S2 is shifted and scaled compared to S1 by an unknown amount (but small; eg shift would be of the order of 1-10 samples). What is the ...
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23 views

Finding defects in wall paint (finding difference in textures)

I have been experimenting with computer vision techniques to find defects in paintings, more specifically defective brush strokes. I have tried a handful of techniques such as different filters, One ...
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2answers
78 views

Indices in 2D Convolution Operations - Handle Out of Bounds Indices

Referring to the answer here: https://www.quora.com/Why-are-convolutional-nets-called-so-when-they-are-actually-doing-correlations, the equation for a discrete 2D convolution is specified as: $$C(x,y)...
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55k views

OpenCV/C++ connect nearby contours based on distance between them

I have to connect nearby contours in an image based on the distance between them which specifies if the contours are to be connected. Now there's a question already on the same problem here https://...
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1answer
30 views

Different representations of frequency space of 2D image FFT

I'm learning images processing using FFT. In my test example provided below the input pixel values are clamped 0-1 (0-255), but I do eventually want to process floating point heightfield pixel values....
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17 views

Reconstract the image from the modulus of its Fourier transform

In Reference, it is shown than one can recover the image by using only the modulus of its Fourier transform. It provides two iterative algorithm which is really similar to Gerchberg–Saxton method. ...
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3answers
64 views

confusion sampling vs quantization?

while converting analog signal to digital equivalent,we have a process that is called analog to digital conversion and it has two main steps/stages sampling and quantization? I am confused whether y ...
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0answers
32 views

Calculate velocity of an object? [closed]

I have a video of a ball travelling through a video and I would like to calculate the velocity of the ball(in mph) at each point in time. I have detected the exact position of the ball in each frame ...
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11answers
16k views

Is deep learning killing image processing/computer vision?

I'm looking forward to enroll in an MSc in Signal and Image processing, or maybe Computer Vision (I have not decided yet), and this question emerged. My concern is, since deep learning doesn't need ...
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1answer
2k views

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

Iam 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::...
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video resources for learning image processing?(for EE background)

Please kindly recommend some youtube links for learning image processing. I have EE background and i want to study/learn image processing in this way Also i have confusion that Computer science ...
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2answers
314 views

Anisotropic Diffusion Filter - Intuition Behind Parameters

I need to know what is iteration and divergence in anisotropic diffusion filter technique. Isotropic diffusion $$\frac{\partial I(x, y, z)}{\partial t}={\rm div}\left[c\cdot \nabla I\left(x, y, ...
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1answer
185 views

Correlation Performed by Convolution

Background: The question here is related to images in particular and not signal/waveforms. I have been reading a lot of answers about the difference between convolution and correlation but I am stuck ...
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1answer
57 views

How Can an Object Move by Less Than a Pixel Between Two Consecutive Frames?

I think video is a series of picture frames. Consider a black & white scenario (no RGB). A picture frame is a 2D array of pixel. Each pixel has a single color. A pixel can't be half black or half ...
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0answers
27 views

How to create different Time frequency images from a data

I'm new to Python. I have a time series in a CSV file that has about 5000 rows and 3 columns. I have split the data into training and testing in ratio 70:30 respectively. However, I have a problem ...
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2answers
37 views

How to find position, scale and rotation of a known shape/contour in an image?

I have an image of an object. The image shows a high contrast outline of the object. It is guaranteed that the image shows exactly one object. The shape/contour of that outline is known. It is not ...
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0answers
6 views

Image extraction post processing to increase similarity

I’m trying to train an OCR model, but I need to get my extracted images to look more like the training images. However I’m not sure of how to go about it and what techniques I can use. For instance ...
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1answer
541 views

The Kernel in 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 ...
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3answers
86 views

3D model from high speed videos?

Is there a way to convert or somewhat replicate RADAR data from a set of given high speed videos taken from multiple angles. The problem is quite ill defined but the task I have in hand is to ...
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1answer
697 views

How is WSNR (weighted signal to noise ratio) defined?

I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights. I ...
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13 views

How can I get better results from Phase Correlation

I am using Phase Correlation to register 3D data. There's a clear distinction in the y direction so the resulting shifts seem to be correct. But since there is a lot of similarity in the x direction ...
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2answers
1k views

Shifting in DFT (FFT)

Input image Listing-1 i = imread('Untitled.png'); i = rgb2gray(i); F = fft2(i); %%%F = fftshift(F); F = abs(F); F = log(F+1); F = mat2gray(F); imshow(F); ...
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130 views

How Is the Gaussian Kernel Related to the Euclidean Distance of the Neighborhoods in the Non Local Means Denoising Algorithm?

I am reading the paper A non-local algorithm for image denoising that describes the original non-local means algorithm. They define (p. 3 of the pdf) the distance between two square fixed ...
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1answer
491 views

How to use the Walsh-Hadamard transform to filter 24 bit RGB color values in a localized spatial region?

After reading this Signal processing Stack Exchange article tonight, What is the Walsh-Hadamard Transform and what is it good for?, I became interested in applying the Walsh-Hadamard transform to ...
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1answer
310 views

Looking for Open Source Image Processing Library that is equivalent to HIPS

Note -- would appreciate any comments on ho to improve the question -- I did the best I could but it I feel it may still be sup-par. HIPS was/is an excellent image processing software. It was ...
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1answer
106 views

How to Describe the Color of an Image Patch?

I want to describe the color of an image patch (say, of size 5x5) centered around a pixel of an RGB image. The most straightforward way to do that is to calculate the average color over that patch and ...
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1answer
119 views

What is the relation between time, frequency, spatial and spectral domains?

What is the relation between time, frequency, spatial and spectral domains? I think that time and spatial domains are the "original" domains (e.g. if the signal is a greyscale image, then the domain ...
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2answers
72 views

How do I denoise a microscope image?

I'm working in a computer vision project, where the goal is to detect some specific parasites, but now that I have the images, I noticed that they have a watermark that specifies the microscope ...
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3answers
1k views

What Is the Cause for Poor Results with Adaptive Thresholding?

I try to run text cleaning process based on the camera captured image. By using OpenCV adaptive threshold method with parameter ...
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5answers
34k views

How to Remove a Glare / Clipped Brightness from an Image?

I have an image Is there any way of removing the bright white spots ? Please help thanks Edit: After operating with gaussian and then displaying using imagesc get the following output which ...
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2answers
1k views

Why is zero padding required for Sobel edge detection?

Why do we leave two rows and two columns of an image (or) padding zeros to an image for detect edges while using Sobel operator and Prewitt operator?
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1answer
1k 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 ...
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1answer
144 views

How to add additive noise to an image?

I have the following image I and I want to add additive noise using the array N below. Can you please give me a calculation example of how to achieve this? Do I have to move from image space to ...
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1answer
321 views

Programming the IDWT for image processing

I want to program the 2D inverse discrete wavelet transform (only 1 level) in the case of image processing. In the matlab website there's this diagram: now, I want to program the IDWT with haar ...
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1answer
52 views

Fresnel transform over image

You can recommend the literature or tell you what the Fresnel Transform does to the image. I realized that this describes the passage of a light wave through an optical element, but I need to ...