This tag covers signal processing where input is an image, such as a photograph or video frame and the output could be an improved or altered image, parameters related to the image or information about features within the image.

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9 views

3D effects like HTC One Dimension plus

Its true that HTC one M8 uses dual camera to achieve the 3D Dimension plus effect, but can anybody tell what is it called, if its a series of image manipulation? Demonstrated here, Video
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1answer
22 views

Trying to translate formula for blending mode

I am using OpenCV C++ for making the blending mode like in photoshop, I want to make overlay mode in it. I search its alternate in OpenCV in which I found this ...
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0answers
17 views

How vibrance method of photoshop work in opencv

Can somebody please explain how Photoshop vibrance function can use in opencv c++ ? so that I may reproduce the same effects in my application. Here is the vibrance ...
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1answer
49 views

How to calculate the local gradient of an image in MATLAB

I know that the gradient function is supported by matlab, but the local gradient is not, so how do you calculate it?
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0answers
11 views

Haar wavlet Transform in OpenCV

I am new to OpenCV. I am working on implementation of Haar wavelet transform of an image in OpenCV in C++. Please anyone suggest me how to implement?
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2answers
40 views

measure angle between two lines, can rotation center constraint be used to refine the initial measured result?

I'm trying to measure the angle between two needle positions in an analog meter (gauge). such as: After the image processing of several images, I get the processed image below(a image show different ...
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0answers
24 views

Which method overcome false edge problem [on hold]

I have one problem that is false edge problem. Given a image with real edge and false edge. How to detect where is real edge? Which method?
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0answers
11 views

How can I calculate the Gaussian range and space parameters in a bilateral filter?

Let's suppose I have the following [4x10] image: 1 3 4 5 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 5 3 5 6 8 9 0 0 2 3 4 6 7 8 9 0 8 9 How can I calculate its space ...
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1answer
11 views

New capture card YUV 4:2:2 leads to different images

I have just bought a new video capture card whose output format is YUV 4:2:2 (as my old one) and surprisingly when I capture images with both cards I get different results. Differences are very small ...
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0answers
14 views

linear contrast stretching based on minimum and maximum calculation from image histogram

I'm studying Gonzalez image processing book and under the topic linear contrast stretching based on minimum and maximum calculation from image histogram has been ...
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2answers
22 views

Need samples of big endian encoded tifs [closed]

Folks I've written a small utility that extracts some (and only some) header information from Tifs. To test it fully I need some Big Endian Tifs, but I cant find any, and I can't find anything to ...
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1answer
49 views

Best method to segment a given image

I have one image. I want to segment it by simple approach. Could you suggest to me the best method to segment it? I think one of them is gradient or FCM. But I am not sure. Please see my given image ...
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1answer
39 views

What does the 420 means in YUV420?

I'm not sure if is the correct location for ask this question. If not please info me the correct StackExchange site. As this wikipedia page show, there is one YUV format of image as YUV420 and YUV411. ...
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1answer
17 views

PNG IDAT specification

I'm going over the W3 PNG specification (creating a PNG library from scratch) and I've finally found how to create a green 1x1 image. Now I'm trying to create a bigger image of mixed Red, Green and ...
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3answers
74 views

What is benefit when convert signed 16 bit to unsigned 8 bit in medical image?

I have an image with its type is 16 bit signed. I see some paper, the author often convert it to unsigned 8 bit. But they did not explain why they do it. Could you explain what is benefit of this ...
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1answer
72 views

How to make filters?

I am trying to make filters like sepia filter in my app like other photo editing applications , till now I don't have any idea about it , Can any one help me out ...
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0answers
99 views

Image Processing/Analysis for Eye blink detection

I am working on a eye blink detection project in Matlab. By this moment I have been successfully extracted the images of pupil of eye from the real time video captured via a web cam. But I am stuck ...
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0answers
15 views

Meaning of tight frame in the context of texture synthesis

I am currently reading "A parametric texture model based on joint statistics of complex wavelet coefficients", by Portilla and Simoncelli. In this article, they use the "steerable pyramid" to ...
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0answers
31 views

Dice Similarity coefficient for 3D image?

I am want to calculate Dice Similarity Coefficient (DSC) for 3D image. I done it for 2D. But I don't know how to apply it or change for 3D. Could you help me to find the way to calculate DSC for 3D ...
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1answer
24 views

How to unify the color and brightness measure of two given camera?

I have two cameras, and I'm up to perform some matching stuff on videos captured by these two cameras since I'm a CV guy. The problem is the two cameras have very different performance in terms of ...
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1answer
37 views

How to get histogram data object from matlab

Lets say I have a matrix x=[ 1 2 1 2 1 2 1 2 3 4 5 ]. To look at its histogram, I can do h=hist(x). Now, ...
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1answer
47 views

What are True Positive and False Positive with reference to image processing

Say for instance, face detection algorithms - I see researchers testing their algorithms and table their results under TP and ...
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0answers
91 views

How do I plot color distribution of HSV image in matlab

I have a dataset of images representing human skin. How do I plot the skin color distribution in HSV color space and YCBCR color space. However, I'd like ignore the "value" or "brightness" in both ...
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1answer
58 views

What's the frequency transform of a random matrix?

Assume the following: img = 255*rand(512); %Generating a 2D matrix with random numbers between 0 to 255. fftimg = abs(fft2(img)); %FFT of the image. The frequency transform of this image is a ...
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1answer
27 views

diffusion filter

I need to know what is iteration and divergence in anisotropic diffusion filter technique. here 't' refers to iteration what is this iteration.how it is related with filtering. I know that iteration ...
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2answers
53 views

concept of image rotation

i am trying to understand how does the image rotation occur? i studied and came to know that we just multiply the image coordinates with rotation matrix which gives us the value of new coordinates. ok ...
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0answers
53 views

Slicing of images

I have used the following command to slice a large image into blocks of 2x2 pixels: convert -crop 2x2 +repage Logo.jpg sl%d.jpg When I attempt to put the blocks ...
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2answers
83 views

What is the difference between a one dimensional and a two dimensional signal?

If a signal depends on only one variable then we call it one dimensional, and if a signal depends on two variable we call it a two dimensional signal. But when we represent an one dimensional signal, ...
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3answers
112 views

What technique can I use to remove useless information from an image?

Is there any way to remove useless information (unimportant details) from an image? If, for example, we have a specific image, so this contains both useful and useless information. If this image can ...
2
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2answers
102 views

How do you interpolate between points in an image (2D), e.g. using splines?

I can understand just fine how to use 1-dimensional interpolation on data points where one coordinate is a function of the other: y = f(x). However, when we have an ...
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3answers
144 views

What does the negative sign mean in the image frequency domain?

When I transform an image from the spatial domain to the frequency domain, some frequencies are negative. What is the meaning of the negative sign? For example:
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2answers
90 views

Inverse Fourier Transform

It's well known that convolution in the spatial domain is equivalent to multiplication in the frequency domain. i have multiplied the Fourier transform of an image F with H. where H is the FT of a ...
4
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1answer
187 views

Understanding Spatial Frequency of Images (using matlab)

I wish to isolate a crosswalk from its surrounding, and I thought that as crosswalks have a repetitive pattern of thick white stripes, I might be able to isolate them by measuring their frequency ...
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4answers
67 views

What is Hue and Saturation?

I have difficulty in understanding what is Hue and Saturation. please explain what is hue and saturation to me with an example or analogy.
2
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1answer
80 views

How to detect quadrilaterals in a point cloud?

How can I detect a quadrilateral in a point cloud that looks almost like a rectangle? How do I set the criteria (i.e orientation, size etc) to get the shape for example in the image below?
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1answer
70 views

How the select the representative frame when detecting vehicles

I am detecting vehicles from the video (taken with a camera), and the vehicle detection part works fine. My problem is that I should always extract only one representative frame per vehicle, and not ...
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0answers
110 views

Removing a sinusoidal artifact from a set of movie frames

I am doing some post-hoc analysis of a dataset consisting of a series of movie frames that are contaminated by a strongly periodic artifact. I would like to remove this artifact from my frames. For ...
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4answers
85 views

What is a labeler?

My computer vision / image processing professor uses the term "Label", to represent part of an image, but cannot explain in a way that makes any sense to me what it is. She says this is a somewhat ...
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0answers
30 views

looking for a way to compare bunch of images

I have about 4000 NxN images. All those images are taken for the same object in the same light background with the same camera but there might be noise so most of the pixel should be about the same ...
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1answer
66 views

Purpose of eigenspace of covariance matrix of a blob?

Given a blob of an image (representing an object), according to Wikipedia, we can compute the co-variance matrix using the image moments. I understand that the eigenvectors of that matrix can be used ...
4
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2answers
251 views

Discrete Fourier Transform: What is the DC Term really?

I am currently toying around with the Discrete Fourier Transform (DFT) in Matlab to extract features from images. I like to fully understand the concepts that I use. I have read several explanations, ...
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0answers
37 views

Shadow removal from gray scale single image and unknown light source

I look for a paper that treat the case of shadow removal from a single grayscale image where the shadow is created by a unknow light source.
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1answer
53 views

Object recognition using color information

I want to use the L*a*b color model for recognition of a particular colored object by calculating the euclidean distance between the desired color in current image and the same color in next image ...
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0answers
26 views

Need to understand how wavelet is applied on Image matrix?

i want to understand ,how to find out Discrete wavelet transform of image 4 by 4 size using Haar wavelet on paper ?
2
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1answer
99 views

calculating SNR of image in blurred image

I have a noisy image $X$, I want to apply the Wiener filter on it and get a deblurred image $Y$. I'd like to measure the SNR in both in order to evaluate the quantity of noise deleted. I know the ...
3
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1answer
1k views

Difference between correlation and convolution on an image?

Could you please clearly explain what is the difference between correlation and convolution that is down by a filter on an image? I mean in terms of signal processing definition I know that ...
2
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1answer
89 views

Histogram evaluation for image quality concerning illumination

I'm currently trying to develop an algorithm to control the camera characteristic of a camera (the camera characteristic can be controlled to adopt it to the different lightning situation which can ...
8
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1answer
124 views

Remove artifact from space probe image

This is a photo of our homeworld, taken by the Juno spacecraft recently, sling-shotting on its way to Jupiter. What it gained in speed, we lost in ours, however thankfully we will not be falling into ...
1
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1answer
97 views

Image Registration and optical flow

Image registration algorithms can be classified into intensity-based and feature-based algorithms, I want to know When and Why should i choose intensity or feature based algorithm? another question ...
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0answers
22 views

Can I use Image entropy in noise removal algorithms, in order to chech their effectiveness?

I am working in digital image restoration field, I have studied number of image noise removal research papers, and all of these papers are using PSNR to check the effectiveness of their algorithms, ...