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
votes
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
votes
1answer
22k 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.
10
votes
5answers
979 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, ...
9
votes
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 ...
1
vote
2answers
3k views

white noise in images

For digital images, noise is assumed to be additive gaussian white noise. I remember noise in images is considered as high frequency. However, from the link https://en.wikipedia.org/wiki/White_noise, ...
0
votes
0answers
55 views

IQ to RF conversion

I appreciate any help: I wanna convert IQ data to its RF data, representing an image. The centre frequency and sampling rate are available. What I do is: First I do up-sampling in MATLAB by ...
14
votes
3answers
30k 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, ...
3
votes
2answers
1k views

Poisson noise and curve fitting - denoise first?

If I have an image that is severely corrupted by Poisson noise, and I want to fit a function to the image, is it "better" to attempt to denoise the signal first before fitting, or should I move ...
9
votes
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 (...
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. ...
6
votes
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 ...
4
votes
3answers
2k views

Gradient Domain Reconstruction - Scaling Problem

I am implementing reconstruction of image from gradient domain. This requires solving the following partial differential equation (a Poisson equation) on a 2D grid: $$\nabla^{2}I=\mathbb{div} G$$ $\...
3
votes
1answer
7k views

What does zero-mean noise mean?

I don't know where to start from. and this question might be very silly, I have found such as comment from someone at here, "I think if you noise is zero-mean it doesn't matter, if not it does (...
3
votes
1answer
5k views

Which method to remove small unwanted region and fill holes

I have a hard problem that need your help. I have a binary image that maintains some unwanted region (small white dot) and hole regions (in figure 1).My idea is that the first I will remove unwanted ...
1
vote
2answers
367 views

Why does gamma correction of image use two different definitions of gamma?

I've noticed that the gamma value used in level adjustment of Photoshop and Canvas is 'opposite' of gamma values defined in Wikipedia or MATLAB imadjust ...
1
vote
1answer
2k views

OFDM transmitter data rate

i am simulating OFDM transmitter in matlab....As u all know OFDM consists of different sub systems such as FEC coding, Bit interlever , Modulator , IFFT block and Adding cyclic prefix.... i have ...
1
vote
2answers
1k views

Running the BM3D Denoising Algorithm in Python

I am looking for a strong baseline in image denoising and therefore wanted to have the BM3D algorithm in my benchmark. These 2 python implementations: https://github.com/ericmjonas/pybm3d https://...
1
vote
2answers
89 views

maximum contrast using linear gery-level trasformation

this was a question i found online. given an image with values between [0,1]. how can I get the maximum contrast using linear gray-level transformation? something like I(x,y)=A*I(x,y)+B , where I is ...
1
vote
0answers
35 views

What should I know about Morphological processing [duplicate]

i'm studying my first year as technical student , and we are studying image processing, so last week we got delivered a topic to work on : Morphological processing /opening , i'm trying to dig deeper ...
1
vote
2answers
448 views

relation between luminance and eigen values of an image

There are some research papers in the literature which apply Singular Value Decomposition (SVD) on an image to decompose the image matrix into U, ...
1
vote
1answer
305 views

Which Approach Is Better for Decomposing an Image into High Frequency and Low Frequency Components?

Which approach is better or there is mathematical justification for using Bilater filter and Fourier Transform to decompose a image into High Frequency and Low Frequency Component. Both Bilateral ...
0
votes
1answer
62 views

How to calculate x and y of any object inside an image when stretched?

Suppose a image has Height = 200px; Width = 100px; A point in that image which has Y axis = 40px X axis = 30px Now if I ...
0
votes
2answers
67 views

How to represent a given equation more clear, profressional and short form?

I have a image $U_{m \times n}:\Omega \to \mathbb R^2$, the output $P$ can be define as $$P=\mu J_{m \times n} - U$$ where $\mu = \max \{ u_{ij} : 1 \leq i \leq m, 1 \leq j \leq n\}$, $J_{m \times n}$...
0
votes
1answer
3k views

How to transform SoundWave Picture to sound?

I would like to recreate a sound from a picture of a soundwave. But i see a lot of theorical question. And im not sure its possible.... I mean, it is possible to create a sound... But to make ...
0
votes
1answer
227 views

What is the difference between domain and range filtering?

In the context of image processing, I have heard the expressions "domain filtering" and "range filtering". What do these terms refer to? What is the difference between them?