Questions tagged [image]

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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19
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1answer
40k views

Difference Between Correlation and Convolution in the Context of Image Processing

Could you please clearly explain what is the difference between correlation and convolution that is done by a filter on an image? I mean in terms of signal processing definition I know that ...
16
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1answer
23k views

How to Extract High Frequency and Low Frequency Component Using Bilateral Filter?

What does High frequency and low frequency component signify in an image. How to separate out the high frequency as well as low frequency component of an image using Bilateral filter.
16
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2answers
617 views

3D reconstruction of an image based on depth of intensity levels?

Is there anyway of segmenting objects based on how far they are from the viewer? Can color values assess this sort of a thing for us? How will intensity levels help in determining how far the object ...
14
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3answers
902 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?
14
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3answers
31k 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, ...
14
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1answer
4k views

Automatic Cropping of Arbitrary Shapes

I have an arbitrary shape defined by a binary mask (gray = shape, black = background). I would like to find a largest possible rectangle containing only gray pixels (such rectangle is pictured in ...
13
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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 ...
12
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3answers
1k views

Does a simple photograph contain more information than a complex painting?

I hope this question is appropriate for this site. I came across this passage in The Three Body Problem, a novel by Liu Cixin: The professor had put up two pictures: One was the famous Song ...
12
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1answer
4k views

Who is Barbara (test image)

In recent years I've started doing work in image analysis and have used the Barbara and Lena images. Early on I became aware of the interesting history surrounding the Lena image and that got me ...
12
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1answer
976 views

Image Denoising with Better Edge Preservation

I have the input image : and the output of vein detection for the leaf using a Gabor filter, but the output is really noisy: I tried using Total variation denoising however the results are not good: ...
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5answers
1k views

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

I have a task at hand where I need to detect angle of an image like the following sample (part of microchip photograph). The image does contain orthogonal features, but they could have different size, ...
10
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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 ...
9
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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 ...
9
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2answers
5k views

Wavelet Transform

I want to perform 2D haar discrete wavelet transform and inverse DWT on an image.Will you please explain 2D haar discrete wavelet transform and inverse DWT in a simple language and an algorithm using ...
9
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1answer
11k views

3D Position estimation using 2D camera

I have a camera (iPhone), I have a 3D control object in the image that I know its properties very well. (My control object). There is also a secondary object in motion. The ultimate goal is to ...
9
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2answers
7k views

Phase Correlation - Poor Performance on Noisy/Blurred Images?

I have successfully tested 1D phase correlation algorithm to determine vertical shift between two synthetic images. When I moved to real images, however, it is not able to detect translation at all (...
9
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1answer
867 views

Removing Noise from Dental Radiography

I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each ...
9
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4answers
254 views

What is the type of noise in this image?

what reason could make the noise/effect in this image? Below is the original Thanks!
9
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1answer
234 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 ...
8
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3answers
2k views

FFT for line detection

I am trying use the FFT in a different way then most people ask about. I want to be able to take a picture of a graph with regular repeating vertical lines, and to process the image to determine how ...
8
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1answer
2k views

How to remove reflections from images?

I've been playing around with making images better and removing all the unwanted disturbances from it. I found out a major concern would be removing the unwanted reflections that might come. I've ...
7
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1answer
1k views

Is an image a random variable or a random process?

Is an image a random variable, where each pixel is a realization of the same random variable? Or is an image a collection of random variables (if an image is of size mxn, there are mxn distinct random ...
7
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2answers
12k views

Measuring the contrast of an image

For a project, I want to measure the contrast of a global image. I want to compare different images to get the image with the best contrast. I know about the Weber contrast, but I need a normalized ...
7
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2answers
29k views

How to apply watershed to segment images using matlab?

How to segment this image using watershed to retrieve only the people in the image ? I have done the following so far : Calculated a gradient Calculated the watershed transform My code: ...
7
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3answers
250 views

Determining Toy Helicopter Orientation From Image

I am working on developing an autonomous control system for toy IR remote-controlled helicopters (like the Syma s107, for example) using a webcam and an Arduino with some IR LEDs. I am using C++ with ...
7
votes
1answer
509 views

White Road Sign Detection [duplicate]

Possible Duplicate: How to extract traffic signs from a photograph? I am working on a project which involves detecting north american speed signs (black/white) using a 720p HD camera. My problem ...
7
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1answer
1k 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 ...
7
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2answers
834 views

Calculating the SNR of a blurred image

I have a blurred and noisy image $X$, I want to apply the Wiener filter on it and get a deblurred and denoised image $Y$ (i.e apply inverse of blurring filter while at the same time reducing some ...
6
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1answer
3k views

Blending Artifacts in Photo Stitching

I am working on a photo stitching application that uses multi-band blending. I need to get rid of unpleasant edges appearing at some places: Here is the area of overlap (left - new image added to the ...
6
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3answers
3k views

What is the difference between MSE and PSNR of images?

I have some doubts. What is the difference between quality parameters MSE and PSNR? Which is used when? Is there any advantage of PSNR over MSE or vice versa? Also I have heard people saying that ...
6
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2answers
2k views

Random Noise Removal In Images

I'm trying to remove random noise from an image. The noise is arbitrarily random so it must not necessarily follow a certain distribution (Not every pixel has the same chance of being affected by ...
5
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5answers
11k 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.
5
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2answers
2k views

Commonly used test image sets

In the image analysis literature there are a variety of ways people show the usefulness of their method. For example, performance on an ideal signal corrupted by noise, an artificial signal ...
5
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1answer
278 views

Does every 8 by 8 DCT matrix have a valid (in range) IDCT?

For a given quantization level of JPEG compression, are all possible DCT matrices have valid IDCTs. By valid, I mean matrices whose elements are in the range [0,255] ?
5
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1answer
502 views

Online boosting (training on the fly) for face detection

I want to implement an on-the-fly training process for face detection. I'm not sure but it seems it's called online boosting. Вefore, I have used OpenCV face detection with my own cascades, but I'm ...
5
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2answers
848 views

Which 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 ...
5
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1answer
325 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 ...
5
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3answers
1k views

Finding similar pictures in a database

I have large database of pictures, about a few million. I need an algorithm to find pictures which are similar to those in the database, up to a scale factor or a crop and shift (I have only these ...
4
votes
1answer
4k views

8*8 block matrix in JPEG image compression?

In standard JPEG format of a image, Discrete Cosine transform is used. But instead of applying the transform on whole image, we first divide the image in 8x8 block and apply transform on each of them. ...
4
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1answer
2k 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 ...
4
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1answer
2k views

Performing DFT twice on an image. Why am I getting an inverted image? [duplicate]

I was asked to perform DFT on an image twice as a part of my school assignment. Why am I getting a blurry inverted image when I perform DFT on an image twice? Sorry, I'm new to image processing and ...
4
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2answers
571 views

How Can I Remove Flickering Background in a Video?

I have a black and white video taken with a high speed camera and I notice a background flickering coming from my LED light. The images alternate from dim to bright and it makes the videos quite ...
4
votes
1answer
469 views

Denoise images with wavelets

I try to understand what following algorithm from this gimp plugin does to denoise an image: ...
4
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3answers
716 views

Local Image Features Extraction for Road Signs

I'm working on a project to detect a road sign from the Image. Consider the sample image below: I'm using a heuristic search to detect the road sign within an image. Basically, I want some weak ...
4
votes
1answer
312 views

Signal Processing using Fourier Transform

So I'm trying to understand how MRI machines work. I understand all the concepts of it, the parts, what they do, how the machine works, etc. The part I'm having trouble with is the fourier transform ...
4
votes
1answer
2k views

Fourier transform possible on non-rectangular part of an image

Dear Signal Processing readers, I want to introduce 'noise' into parts of images. Until now, I worked with rectangluar images for a similar purpose and did the following, using (inverse) Fourier ...
4
votes
1answer
181 views

Are There Common Values of Standard Deviation for Gaussian Noise of an Image?

For example, it occurs to me that there might be a standard deviation value of Gaussian noise in which the human eye could no longer distinguish an object because the standard deviation is very high ...
4
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4answers
826 views

Upscaling detection approach

I'm trying to implement a solution that would, to some extent, evaluate a picture telling what are the chances that it was upscaled from the smaller image. My approach is as follows: Take a picture ...
4
votes
1answer
13k 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. ...
4
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1answer
2k 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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