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# 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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### How to expand on and deepen a basic skill set for image/video processing?

I didn't take any class on image processing but I studied the subject based on lecture notes and important books for last three months. So at this point, I would like to sharp my image processing ...
1k views

### Confused about HSI and HSL color spaces

I am reading a book for image processing algorithms (Andreas Koschan, Mongi Abidi: Digital Color Image Processing) and for the contrast algorithm it says that I can either go ...
159 views

### How do I rotate a warping grid without changing the warped image's orientation?

I have a warping grid, that has to be applied to an image. When I apply the grid, I get the results I expect. Now, I want to apply the same grid to the same image, but the image is modified in the ...
314 views

### How to match a drawn Chinese character to a database of stroke animations

I have a database of Chinese character stroke animations. Each entry is basically a set of points which shows how and in which order a character should be drawn. To make lookup easier, I would like ...
66 views

### Path Center Correction

So I have groups of (x,y) coordinates that I'm using to draw lines. The lines aren't perfectly straight but they are connected. In a Cartesian plane the middle would be called the origin, but I'm ...
1k views

### Autocorrelation of power spectrum

Anyone have an idea of how I can implement autocorrelation of power spectrum of one image? I tried using: autocorrel = ifft( | fft(power spectrum) | ^ 2 ); but ...
109 views

### Colors on photo to real-life values

The target is to get a color of selected area from taken photo on a mobile device. So I've needed to make some image processing programmatically. Is it exist any algorithm to approximate color to it's ...
3k views

### Tutorial on 2nd generation wavelets (with lifting)?

For some denoising and deconvolution experiments, I'd like to apply a 2nd generation wavelet transform (using lifting steps) to images. I know that there are several implementations available, but ...
2k views

### How to estimate octave and size for visual features positioned at Harris corners

I am currently working with and comparing the performance of several feature detectors provided by OpenCV as basis for visual feature matching. I am using SIFT descriptors. I have accomplished ...
523 views

### What interpolation methods can I use to get the tightest fit for these curves?

I am working with MRI images of the brain that have certain areas marked by hand like and . I am trying to come up with an interpolating function that will let me describe such curves so that I can ...
2k views

### what is the starting point of a contour as given by cvConvexityDefect() function in OpenCV

i have to distinguish between palm and elbow in my contour(I'm using cvconvexitydefect for that purpose). Here's the image: I'm taking contour of left image. the 2 topmost points in right image are ...
6k views

### What is the link between the homography computed over 2 images and the homography computed over the same images upside down?

With OpenCV, I compute the homography between, say, these two images: and Don't worry about the strange white form on the right side, it is due to the smartphone holder I use. The homography, given ...
1k views

### OpenCV detecting elbow

I have to detect my elbow. I'm able to produce an image in which I'm facing the camera, standing before it and my arms are in my body plane(body plane is plane containing my head,chest,and legs)(i.e. ...
425 views

### Detecting meandering rivers in images

I have $n$ surfaces: $z_i(x,y)$ with a measured attribute (variable) on each surface: $a_i(x,y)$. Most of the surfaces will have a random distribution of the attribute across the surface, but some ...
155 views

### Analyzing movement of fringes

I have taken a series of images of a fringe pattern at regular time intervals. This fringes are generated by shining a laser beam onto the CCD camera. The laser goes through a lot of optics, which is ...
6k views

### Alternatives to Hough transform for detecting a grid-like structure

I have an image which is composed of multiple 'angles' which form a grid shape: After some searching, Hough seemed like a good fit, because it isn't troubled by breaks in lines. However, the problem ...
5k views

### Nutrition facts label OCR

My team is working on a program that can read nutrition facts labels using OCR, much like NutriScanner (though by its reviews it doesn't seem like it works particularly well). I've seen other ...
624 views

### What is the best method for merging time lapsed photos? Accessable from python(PIL)

I have numerous photos from a still image camera that I would like to merge into one photo to allow for easy spotting of motion or new objects. There is a bit of noise across the photos but not very ...
4k views

### Standard Deviation in Gaussian Blur

I have a function that performs gaussian blur on image for some specific $\sigma$ (the standard deviation). It first computes kernel of size $\lceil 3\sigma \rceil$ and then performs convolution with ...
575 views

### Extracting top & bottom fields from a YUV 4:2:0 Frame

I am wondering what would be the right approach to extract top and bottom fields from a YUV 4:2:0 frame. In the YUV 4:2:0 representation, Luma and Chroma samples are located as shown below: Y Y Y Y ...
1k views

### Auto-focus estimation?

What kind of analysis might be used on sets of 2D monochrome image matrices or bitmaps to estimate or compare their relative quality of being "in focus"? Is there an efficient way of computing a ...
164 views

### Example image that is degraded by shot noise and easily misinterpreted?

For illustrating the effects of shot noise (more precisely, emitter failure in fluorescence imaging) I am looking for a good example image. The image should ideally be easily misinterpreted, ...
217 views

### On the de-noising of time-frequency images

I am wondering what techniques might be available for 'de-noising' the following example time-frequency image that was created using Welch's method. The following plot was created from a robotic ...
761 views

### What's the unit of spectral intensity in calculation of RGB tristimulus?

According to CIE color space and relation of RGB with XYZ, we can express $$R = \int_0^\infty I(\lambda)r(\lambda)d\lambda$$$$G = \int_0^\infty I(\lambda)g(\lambda)d\lambda$$ B = \int_0^\infty ...
138 views

### Resources on ridgelets/curvelets

Can you suggest any good introductory resources on ridgelets and/or curvelets for image processing purposes? I'm considering buying Sparse Image and Signal Processing: Wavelets, Curvelets, ...
397 views

### Anti-Filter in Image Processing?

Is there something like an anti-filter in image processing? Say for instance, I am filtering an image using the following 13 tap symmetric filter: {0, 0, 5, -6, -10, 37, 76, 37, -10, -6, 5, 0, 0} / ...
818 views

### What does it mean in image processing when a filter is called non-linear?

In image processing, what does it mean when a filter is called non-linear? Does it mean the equation of the filter contains derivatives and if it didn't, it would have been called linear?
200 views

### Detecting Arabic verses spanning multiple lines

I need to build a Quran app and I want to read out the verses when a user touches it. The problem I'm facing is that some verses may expand to one and half lines (highlighted red verse) or just fit in ...
277 views

### Advise on detecting anatomical landmarks in a CT reconstructed volume

I'm trying to automatically detect some medical defined anatomical landmarks in a CT reconstructed volume. Medical doctors use these landmarks to measure some patient specific parameters. I have ...
1k views

### Padding Images To Solve Inverse Filtering Problem?

Let's say that the point spread function, h, is known for a blurred image B. If we want to apply an inverse filtering method (eg. Direct Inverse Filtering for noiseless images, Wiener Filter, ...
703 views

### What is the antialiasing algorithm employed by video cards?

What is the algorithm employed by video cards when one talks about for example 8xAA? I thought the algorithm was about looking at neighboring pixels for correction. ...
1k views

### Necessary image processing operations before template matching

Well, this may show I didn't take image processing class. I have this template to match an object in images. But real object in images, for example, does not look like that but the second image. What ...
93 views

### Viewpoint dependant deformation of objects in photos

I have a question concerning the deformation of objects in photos. Which deformations can an object depicted on a photo undergo through viewpoint and condition changes? Some deformations I have in ...
133 views

### References and resources on hyperspectral (multispectral) image processing

Due to my work, I just started studying hyperspectral or multispectral image processing. I think I have enough programming background and studied mathematics for my degree - it was long time ago ...
157 views

### Struggling to find a good definiton for Gabor-Descriptor

I am attempting to implement the Gabor Descriptor based on the following paper Image Copy Detection Using a Robust Gabor Texture Descriptor. It is the best paper that I have found on the subject. It ...
981 views

### How to recognize colors from the color chart?

I am developing a vision application that is using the color chart below and camera to extract color of each patch in the chart. In order to do that, I have to first detect the chart area in an image ...
131 views

### How to get to shoulders localization on image photo? [closed]

I have a project on my university. I have to localize from video where are shoulders of person in movie. Do have any advise how to get to this? I thought about corner detection or some kind of ...
1k views

### Examples of linear/logistic regression applications

I was wondering about super simple applications of linear or logistic regression to signal processing (image processing specifically)? I'm a math guy that's been asked to explain some mathematical ...
1k views

### Detecting tennis courts in aerial images? [duplicate]

Possible Duplicate: How to find tennis courts in aerial imagery I am trying to detect tennis courts that are present in aerial images .. I have the following image: I tried color image ...
990 views

### Is there any way to get intensity value of a certain wavelength for given pixel of a normal image?

I understand I can get a color from wavelength but it's not true for the opposite direction. In case this picture would help. To make this question simple, let's lighting and calibration aside to an ...
1k views

### what is the possible solution for the Intra-class variations poblems?

my poblem is that i have a database for human dorsal hand veins ,but with intra-class variations , so this problem have a large effect on my results when i need to do matching between my samples for ...
86 views

### How do I keep a value between known bounds in an open system?

I detect points in images with an algorithm. The only parameter is a threshold T that I can modify at each image. Such images are from a continuous video, so each ...
978 views

### Fast approximate optical flow / image shift

I need to detect how fast a camera is panning (either horizontal/vertical) to give a warning to the operator to slow down. The entire image is moving as a block, I don't need an actual direction (...
226 views

### Identify the correct spot to place a label

In the image shown below, I have a 2D data set where I have identified four clusters labeled [0,1,2,3]. I'm looking for an algorithm to place the labels in a ...
2k views

### How to remove stains from images?

I have this extremely distorted and stained image Is it possible to remove this stain ? Could image inpainting help ? Please help EDIT : Another image After applying anisotropic diffusion and ...
65 views

### Conversion between primary colours

Heads up, this is homework. Just a little stumped :) I have some arbitrary primaries, A, B, ...
572 views

### What image-processing techniques are ideal for this particular shift/scale invariant template matching?

A problem I had originally discussed here has evolved, and might have gotten a little simpler as I studied it in some more and attained new information. Bottom line, I would like to be able to detect ...
524 views

### Interpolation algorithms in computer graphics

I'm looking for an image-processing algorithm that uses interpolation (polynomial, spline, doesn't matter). I have to implement such algorithm to process a bitmap for my labs. It can't be image ...