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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How to show Image FFT with origin as DC?

The page Here explains how to do the discrete fourier transform on a 2d image. It mentions this: In most implementations the Fourier image is shifted in such a way that the DC-value (i.e. the ...
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24 views

Problem with image alignment/warping

I am currently working on image alignment. I start with a normal image and then use matlab's imrotate to rotate it 1 degree. Afterwards I calculate my warping matrix and align the image using imwarp. ...
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8 views

How to correctly implement spectral activity measure (SAM) for image quality assessement

I am trying to compute the spectral activity measure (SAM) which is a well-known image quality assessment metric. I used MATLAB to implement this method, which can be computed as follows: $$ SAM=\...
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1answer
16 views

Calculating the perimeter in binary image

After pre-processing, I can obtain the image like this: Then, I want to calculate the perimeter of the bottom region (annotated with grey line). I am making an ImageJ plguin. So I have to implement ...
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2answers
48 views

Remove unwanted object of image in MATLAB?

I am trying to remove the unwanted object. I have an image that includes a house and the trees. I am trying to remove the trees. I am using 'imsubtract' to remove small edge. But the result is not ...
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1answer
35 views

How to get rid of ripples from a gradient image of a smoothed image?

I have a gray scale uint8 image. When I smooth it with a Gaussian filter and then compute the gradient image with a Sobel filter in OpenCV, ripples would appear. The first image is what happens when ...
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31 views

algorithm for segmenting cheese microstructure

I'm trying to get the internal geometry of cheese from images of its microstructure: I tried the canny edge detector and otsu thresholding but neither of these worked very well. I'm guessing that I ...
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4 views

LMN color model vs YIQ color model

LMN color model - L - luminance M & N - Chrominance feature YIQ color model - Y- luminance I & Q- Chrominance feature except formula what is difference between these two?
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22 views

What is the correct way to perform FFT-based convolution?

As far as I know, Obtain the input image whose width/height are power of 2. Obtain the mask/kernel whose width/height are power of 2. The width/height of the mask/kernel must be larger than 3 and ...
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17 views

image analysis: Drawing lines on curvlinear structures and dots on the tips of branches

I want to make an algorithm for: From vascular images like this: I want to plot lines and draw points on the tip of branches like this: Is there any literature or reference? or any idea? I don'...
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9 views

how to open image according to the selected image [closed]

i am using the gui and code for selecting an image is as follows: ...
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7 views

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

In deep learning, we often saw the text "end-to-end learning". However, I do not know that does it means. When is a network called end-to-end training? How to recognize a network is end-to-end ...
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48 views

Is the formula of this image filter correct?

Consider this research paper. In the section 4.1 (Preprocessing), they gave us a formula of the kernel, Where, In the formula, we see that, v is never used....
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2answers
34 views

What should be the dimensions of a Fourier Transformed image?

I have applied Fourier Transform to the following image. I have downloaded this image from the Internet. I re-sized (without maintaining the aspect ratio) it using MS Paint application of Win7 to ...
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31 views

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 ...
1
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1answer
32 views

Obtaining the size of objects from an image

My objective is to be able to obtain the size, in pixels, of objects in images I'm receiving from a camera. I've tried two approaches thus far, both working to some extent, and I'm wondering if there'...
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1answer
25 views

BiLinear Downsample and Upsample Equivalent Filter or Operation

Let's say I have an image mInputImage with numRows and numCols. I resize it using Bilinear ...
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3answers
20 views

Is a real Grayscale image always 8 bit per pixel indexed?

I tested several Grayscale images downloaded from the Internet. Some of them are 8bpp indexed while others are 24bpp (true colored). Looks like different Grayscale images have different depths. For ...
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58 views

using Fisher nonlinear discriminant analysis on handwriting digit recognition

I know basics of Fisher nonlinear discriminant but I don't know how it works on handwriting digit recognition. There is a database for that under this link. However, I have no information on how to ...
3
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1answer
96 views

Making a low pass filter for irregular samples

We are interested in reconstructing the red channel of a scene. The red channel is slowly varying. Unfortunately the camera does not have a Bayer sensor, and the red samples are irregularly spaced ...
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1answer
29 views

Simplistic explanation on PCA eigenface face recognition,

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
31 views

correcting wobbling motion in sinogram

I have measured some sinograms of a specific sample. However, there is some wobbling motion that disturbes the resulting images. Since the red upper and lower lines (indicated with black arrows) are ...
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35 views

Phase correlation vs. normalized cross-correlation

I asked this over at Mathematics Stack Exchange, but since this sort of lies on the border of the questions normally asked over there and the questions you see over here I'll ask it here as well. (As ...
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19 views

Intuitive understanding of 2d deconvolution vs convolution of images in CNNs

I'm looking for an intuitive understanding of the deconvolution mechanism to upsample reconstruct images / upsample feature layers as explained in the work of Mathew Zeiler here and here. I found an ...
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14 views

How to get Harris corners that are present in watershed segmented Bitwise image(road part)?

This is Harris corner image of test image: This is Bitwise watershed segmented image: I want to get that Harris corners which will be in segmented part of image(road part).
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26 views

Deriving an FIR filter that interpolates the missing color components on a Bayer array

Hirakawa and Parks' paper on adaptive homogeneity-directed demosaicing of Bayer-filtered images has a section on designing a FIR filter that, when input one line of sensor data, will interpolate all ...
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27 views

Fast greyscale image segmentation on 16x16 image

I have a 8-bit greyscale 16x16 image where I want to extract coherent shapes with a more or less consistent pixel arrangement if possible (like: a rectangle, staircase, line). Currently, I'm doing ...
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8 views

How to get the inner border of a shape after a dilation

I'm working on custom shapes, like circles, rectangles and so on. Let some variables here: width = W height = H Kernel: rectangle with size: W*H I have to do a ...
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28 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 ...
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0answers
15 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 ...
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1answer
16 views

Question about MRI signal construction

As I understand it, in MRI, a line in k-space is usually acquired while the readout gradient is applied. So during the application of this gradient the protons spin at different frequencies along the ...
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1answer
40 views

Fourier transform of moving image sensor

Consider an image sensor that is moving with some velocity $\mathbf{v}(t) \in \mathbb{R^3}$, and an orientation $\mathbf{R}(t) \in SO(3)$. Treat those vectors as fixed. At a specific time $t$ the ...
2
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1answer
45 views

Gradient of TV norm in total variation denoising

In this link, it says that the gradient is as follow The Gradient of the TV norm is $$ \mathrm{Grad}J(f)=\mathrm{div}\left(\frac{\nabla f}{\lVert\nabla f\rVert}\right). $$ From this other ...
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1answer
34 views

Why can FFT only operate on images with specific properties?

Can FFT only operate on Grayscale images? If Yes, why? Can FFT only operate on images with dimensions of power of two? If Yes, why?
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36 views

Target detection for UAV landing

I would like to detect and track the following target to land an UAV. Target size is $1\rm m \times 1\rm m$. I have tried SIFT + FLANN but there is too few keypoints to have a good match. Have ...
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1answer
47 views

How can I learn image processing in a practical way?

I am a beginner in image processing and I have to learn to program in MATLAB as soon as possible. I started with Rafael Gonzalez book, but understanding this theoretical knowledge and mathematical ...
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17 views

How can I use Hermite Kernel as feature extraction?

I'd read about hermite polynomials, hermite filter and hermite kernel which is I'm not sure if all of these are the same thing. I can't understand how these thing can be used in image processing. Is ...
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1answer
46 views

Confusion about adjoint of convolution

I have the following problem with convolution operators. I know that if I have a filter $g$, then the adjoint filter would be given by $h(x,y)=g(-x,-y)$, so that $\langle g * u,v \rangle = \langle u,...
3
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1answer
61 views

What 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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1answer
56 views

Measuring similarity between two images

I have some images (generated from some processing). Some of those images have approximately the same view of the scene with illumination changes. But there are other images which may show the view ...
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1answer
46 views

Finding the maximum and minimum frequency of a 2D image

Suppose I transform the image into frequency domain and obtain a 2D array of complex numbers. How can I determine the minimum and maximum frequency from that array? By finding magnitude of each ...
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0answers
68 views

Save ROI and background in two images

I'm using MATLAB Training Image Labeler app for labeling images and exporting the regions of interest (ROIs) which I save in .jpeg files.The ROIs are exported as a structure $1\times 430$ with two ...
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0answers
47 views

Annotate a dataset of images

I'll be recording a new dataset using a couple of sensors: kinect, stereovision cameras.. for a project for people detection using only depth information. But I don't know yet how can I annotate the ...
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2answers
69 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?
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2answers
83 views

Image processing - Is mean filter shift-invariant?

Update: So, according to this article. For a 2D mean filter, $$ H[f(x,y)]=\frac{1}{NM}\sum_{k=0}^{N-1}\sum_{p=0}^{M-1}f(x-k,y-p)=g(x,y)\tag{1} $$ $$ g(x+x_0,y+y_0)=\frac{1}{NM}\sum_{k=0}^{N-1}\sum_{p=...
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1answer
25 views

Smoothed image produces contour-like ripples, yet it disappears in saved image?

I smoothed a grayscale image using a size 10 gaussian filter and display it in Octave (imshow) which resulted in ripples which appears to be contours for image intensity. Yet if I save the image (...
2
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2answers
62 views

How can I implement convolution in frequency domain?

Suppose, we have a bitmap image represented as a 2D integer array, int [,] image2D; whose FFT is Complex[,] fftImage2D; ...
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2answers
146 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 ...
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1answer
28 views

What is an 'Oriented' Band-pass Filter?

In this research paper, Section 4.1 talks about a filter called "Oriented Band-pass Filter". What does it actually mean by 'Orientation'? Also, the article gives a function, $$H(u, v) = \frac{1}{1 +...