# 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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### Image Z Coordinate Clarification

I'm trying to understand 3D image reconstruction, and want to clarify how we can find a z image coordinate. Is the z coordinate for image coordinates (x,y,z) the focal length since that's the distance ...
45 views

### Reprojecting an image to another viewpoint using planar homography

I have an image rendered by a simulated camera in Unity. Using this image and the known (virtual) camera pose it corresponds to, I would like to render a new image from another viewpoint. Having read ...
24 views

### When to use composite filters and when to use separable filters?

I’m a beginner in image processing, and was wondering since seperated (decomposed) filters help give faster and more efficient results, when do we even need to use composite filters? All I heard is ...
1k views

### What are the various techniques for detecting walls in buildings (architectural) in floor plan images?

I have to process building floor plan images to extract walls from the structure. It is trivial in case of binary images; but the images in our case are colored, and have different colored walls. This ...
59 views

### Comparing distribution of vectors with different length?

I have two vectors of different length, each vector contains similarity scores. I need to plot the probabilty density function of the scores in both vectors to compare their distribution using Matlab. ...
43 views

### Help generating non-Gaussian noise

I'm trying to add non-Gaussian noise to an image. The purpose is to synthesize realistic camera noise. I am doing the following: Obtain a noisy image sample by subtracting a low ISO photo from a high ...
119 views

I was looking at a technology which enables virtual advertisement on the perimeter ads in soccer. It's relatively an old technology for a few years back, but I'm surprised to see the quality of it. ...
19 views

### What exactly is "connectivity" between pixels in an image?

So, my professor says that two pixels are connected if: they are neighbours; and their intensities satisfy a specified criterion of similarity. And depending on the type of neighbours they are, they ...
106 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 ...
12 views

### Convert pictures from the same camera with different FOV to pictures with same FOV

I have a camera device that produce two pictures at the time: depth picture with FOV: 87° × 58° RGB picture with FOV: 90 × 65° I expect that they "share" the same objective so their origin ...
18 views

### Finding the system impulse response for 2D system

Im taking a class on medical imaging, but my previous signal processing course did not really cover 2D systems in the greatest of detail. Therefore, I wanted to ask a quick question on determining the ...
38 views

### How to Use Convolution Theorem to Apply a 2D Convolution on an Image

How do I actually apply the convolution theorem? I have my fourier transformed image matrix, and a Fourier transformed kernel, but how do I actually multiply these together to achieve the intended ...
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### 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 ...
688 views

### How to Measure the Intensity / Saturation of a Color in an Image?

I have a task of developing an application to measure the intensity of a color in an image. I am researching about how to go about it. Intensity refers to the purity of a hue. Intensity is also ...
31 views

### Discrete Fourier Transform of 2-D Images

I'm a high school student doing an essay on the applications of the Fourier transform on signal processing, but I haven't been able to find much information when applying the discrete fourier ...
613 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? How Could One Use It in Image Processing?, I became interested in applying the Walsh-Hadamard ...
93 views

### Should Edge Detection Be Applied in Spatial or in Frequency Domain?

I want to ask why everywhere is used to do edge detection in spatial domain and not in frequency domain with FFT of image and apply HP filter. Thank you.
223 views

### Meaning of lines on x- and y-axis of a centered FFT-spectrum of an image

I am currently learning about the Fourier transform of digital images, but I am wondering about one aspect. In most visualisations of fourier transforms of images, a horizontal and a vertical line in ...
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### Image conversion - raw ultrasound data to convex image

As a project, I'm trying to decipher raw data coming from a medical ultrasound device. The data contains a 128x1008 matrix. Each one of the 128 columns represents a sensor element. Each row in each ...
593 views

### What Are the Differences in Four Different Types of Third Order Image Moments (Skewness)?

I am attempting to analyze images using the third order image moment (aka skewness), but I am having trouble figuring out how to do so. As it turns out, there are four different types of third order ...
1k views

### Finding circle in binary image (R, not matlab)

How would I extract the circular area of a binary image which looks like: The two rods emerging from the side of the circle are noise. I know of the hough transform in Matlab. However, I am using R ...
172 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'...
38 views

### Sharpen ridges and valleys

I am looking for a way of sharpening ridges and valleys in the following heightmap I think this problem is slightly different than a regular sharpen operation, because sharpening would affect first ...
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### Designing a 2d low pas filter in fourier domain for an image

Firstly this is not a homework question. I am working on a project and my professor gave me this task so I can also learn about filters and fourier domain. I have a picture that is 2800 x 4500 pixels....
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### Extracting color information from lit regions to adjust shadow regions, HSV space

If I wanted to match the color of a shadow region to the color it is supposed to be in the lit region, would this, purely color information, be preserved in the hue of the HSV space of the image?
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### 1st and 2nd Gaussian derivatives for edge detection

I have a project about edge detection, I made research on internet about filters and read many articles but there is an article talked about using Sobel and Gaussian derivatives then it mentioned &...
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### 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 ...
1k views

### How does image masking work?

I am new to image processing and I am interested how image masking can be used to extract a portion of a image. Have a look at this OpenCV tutorial. In the section Application of Mask, they say that ...
335 views

### What is the Implementation of a Low, Mid or High Tone Dodge or Burn in GIMP?

In The GIMP, and also in photoshop, you have the DODGE/BURN tool to enhance colors in shaded or highlighted regions, which would otherwise be blackish or whiteish. I found empirically that this filter ...
32k views

### How to Calculate the Color Temperature / Tint of the Colors in an Image?

How can I calculate the (black body equivalent) color temperature of the light source illuminating a given image? Below are screenshots of Adobe Lightroom manipulating color temperature and a shift in ...
57 views

### Understanding the Bilateral Filter (Image Filtering)

I asked this question already on StackOverflow and was told to ask it here instead, so I will just copy the content of my question. I do understand the general concept of bilateral filtering and I did ...
85 views

### How would I fit a distribution to this image noise?

I have collected some noise data from a dimly lit CMOS image sensor. The distribution of pixel values is tallied below:- I'd like to be able to simulate this sensor noise. How would I fit a ...
473 views

### How to detect the maximum resolvable spatial frequency of camera?

I am trying to calculate the minimum line pixel width that can be distinguished from noise as shown in the camera test chart in Figure 1 where the thinner lines on the left are getting more and more ...
150 views

### Normalization of signal against reference

I am trying to figure out if there is any standard way of normalizing a sequence such as a time series against a reference sequence. I am not an expert on signal processing but I was hoping someone ...
3k views

### What is a good distance measure for matching SIFT descriptors depending on the distribution of their noise?

I have read some papers about distance measures like Euclidean, Manhattan or Chi-Square for matching gradient based image descriptors like those computed from the SIFT Algorithm (128-D vectors). Most ...
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### Palmprint Identification - Why do we align the images before we use the Fourier Transform?

I was reading the paper PALMPRINT IDENTIFICATION BY FOURIER TRANSFORM by WENXIN LI, DAVID ZHANG and ZHUOQUN XU about identifying persons based on an image of their palm. The first step in their ...
325 views

### What are the keywords to find an algorithm that detects embossed text from a 3d model?

Currently I am doing an acadmic research about an idea which came into my mind lately. I have a 3d model and I want to extract embossed text .. anyone knows any papers? or if it is already proposed? ....
163 views

### Image Processing- ornament detection

So I am working on a project where we are supposed to detect and count the red and gold ornaments in the picture provided in the link below. I am having issues detecting and counting each ornament and ...
60 views

### Develop a simple image classification system by using Laplacian of Gaussian (LoG)

I am tring to write a simple CAD system to classify some images within two groups by using Laplacian of Gaussian (LoG). I am using scikit-image for this tasks and I want to use DNN in keras to train a ...
2k 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 ...
29k views

### Noise Removal from an Image Using OpenCV (Comparison to Neat Image)

I tried removing noise from the image shown below using Median Blur in OpenCV. But i'm not able to remove the colour noise completely as it is done in Neat Image. Any suggestions.? 1. Original Input ...
832 views

### How to select the specific frame with object

I am detecting the object from the live camera through feature detection with svm , and it read every frame from camera while predicting which affect its speed , i just want that it should select the ...
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### Brightness equalization between different images

I am dealing with a proprietary whole slide image format from 3DHistech, namely MRXS. This image is produced by scanning a glass slide biopsy. The scanner takes pictures at certain positions which ...
47 views

### Producing masks from mostly-static-background subtraction when given the background

My data set contains a number of high resolution greyscale images containing a person's face. A single image containing the background without the face is provided. The background is mostly static in ...
242 views

### Why are 8 points needed to compute a fundamental matrix?

Homograpies have 8 degrees of freedom. Fundamental matrices have 7. Essential matrices have 5. To the best I could find, all those matrices are obtained by using the 8 point algorithm. I don't see ...
1k views

### Denoising by DCT and hard thresholding

If I have an image and I find the DCT and then apply hard thresholding on the coefficients and then IDCT then I have attenuated the noise. Can someone please explain in detail or point me to the ...
1k views

### How to get the scale bar of an FFT for a 2d image

I've been analyzing some images from a transmission electron microscope, including their FFTs, and I'm not sure how to apply a scale bar to the FFT images. I have calibrations for the real space image,...
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### How to perform dot annotation for crowd counting in a image file using Matlab?

I have some crowd images having more than 300 people in each image. I want to label each person(i.e. head) with dot annotation such that coordinate of each dot(x,y) is saved in a .mat file. I hope ...