# 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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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 ...
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.
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 ...
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?
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, ...
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 ...
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 ...
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 ...
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 ...
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: ...
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, ...
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 ...
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 ...
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 ...
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 ...
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 (...
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 ...
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!
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 ...
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 ...
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 ...
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 ...
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 ...
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: ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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.
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 ...
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] ?
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. Šefore, I have used OpenCV face detection with my own cascades, but I'm ...
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 ...
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 ...
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 ...
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. ...
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 ...
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 ...
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 ...
469 views

### Denoise images with wavelets

I try to understand what following algorithm from this gimp plugin does to denoise an image: ...
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 ...
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 ...
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 ...
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 ...
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 ...
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. ...