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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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9
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1answer
733 views

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 ...
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2answers
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 ...
4
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2answers
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 ...
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2answers
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 ...
2
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1answer
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 ...
2
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1answer
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 ...
2
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2answers
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 ...
9
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1answer
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 ...
9
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2answers
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 ...
10
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1answer
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 ...
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1answer
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 ...
9
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1answer
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 ...
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0answers
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. ...
14
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2answers
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 ...
5
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3answers
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 ...
16
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2answers
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 ...
4
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1answer
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 ...
3
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2answers
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 ...
5
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2answers
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 ...
5
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2answers
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 ...
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2answers
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 ...
4
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3answers
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, ...
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2answers
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 ...
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1answer
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 ...
5
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1answer
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, ...
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3answers
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} / ...
14
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3answers
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?
12
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1answer
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 ...
10
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1answer
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 ...
3
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1answer
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, ...
10
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1answer
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. ...
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2answers
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 ...
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2answers
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 ...
3
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1answer
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 ...
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2answers
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 ...
9
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4answers
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 ...
4
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1answer
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 ...
9
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2answers
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 ...
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5answers
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 ...
3
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1answer
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 ...
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1answer
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 ...
3
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1answer
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 ...
9
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4answers
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 (...
12
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2answers
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 ...
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1answer
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 ...
2
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1answer
65 views

Conversion between primary colours

Heads up, this is homework. Just a little stumped :) I have some arbitrary primaries, A, B, ...
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2answers
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 ...
2
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1answer
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 ...
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1answer
2k views

Could you describe the effects for varying different parameters of a canny edge detector?

Last couple of questions touched upon Canny edge detector What are the limitations of a Canny edge detector? and Best way of segmenting veins in leaves? The basic outline of the algorithm is as ...
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2answers
1k views

how to remove color of light source?

I have an image source emitting yellow light. Of course, when taking a picture with the light, the image has yellowness overall. How can I remove that color of light from the image? I have another ...