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.
469
questions
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20 views
Transforming large size kernel (filter) into equivalent small size kernels(filters)
I have a problem where I want to convert kernel of large size, i.e., 64x64, into the number of 3x3 size kernels that convolving them with the same input image results in the equivalent output. (It ...
1
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0answers
19 views
Red Color selection in Python and Skimage
I'm trying to load an image from the disk and then to extract just the red channel of it and display it in grayscale with grey colormap but I don't know what I'm doing wrong.. The image should be ...
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0answers
13 views
How to convert this maze photograph into simple black white maze image [closed]
I have several similar ones. It is so pink that it is hard to see for many people. Focusing on the image doesn't help. I want black lines with white gaps- how can I do it? I tried replace color on the ...
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1answer
81 views
+100
Noise Power Spectrum calculation
I want to compute the 1-D noise power spectrum (NPS) for a uniform CT image. The equation of the 2D NPS is as following:
$$
NPS(f_x, f_y) =\frac{1}{N}\sum_{i=1}^N|DFT_{2D}[I_i(x,y)-\bar{I}_i]^2\frac{\...
2
votes
1answer
56 views
2D Frequency Domain Convolution Using FFT (Convolution Theorem)
In the time domain I have an image matrix ($256x256$) and a gaussian blur kernel ($5x5$). I've used FFT within Matlab to convert both the image and kernel to the frequency domain as zero padded $...
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0answers
24 views
What does the HEX output of FF from start to end mean for my .jpg file? Can I still recover my .jpg file? [closed]
I am unable to view a .jpg file I transferred from the external SD card of my cell phone to my Windows 10 laptop. After repeated futile attempts to properly view ...
1
vote
2answers
68 views
Coordinate system in digital image processing
I am trying to understand image coordinate system where I read that it is reversed (http://www.ece.northwestern.edu/local-apps/matlabhelp/toolbox/images/intro28.html) SO if f(x,y) is actually f(y,x) ...
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0answers
25 views
Zero Padding in image reconstruction
I need to zero-pad the image for a better reconstruction but according to my project details, I will be given a Fourier-transformed image so can someone tell me how to pad the image in such a ...
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0answers
19 views
Fourier coefficients of images?
For a continuous function $f$, it is well-known that the decay of $f$'s Fourier coefficients $\hat f_n$ is related to the differentiability of $f$. Some examples:
for a smooth periodic function $f$, ...
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0answers
8 views
Python, Is there a way to find the properties of a subregion within a larger image region?
The goal: I have images with particles that I need to find the area of. Each particle also has four to five sub-regions that I need to know the area of. Think of a bunch of stripped shirts in a ...
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0answers
32 views
Solving for a convolved function inside an integral
I have an imaging system that produces a signal in a pixel, in part, by responding to incident radiance $L(\lambda)$ that passes through a filter with transmission $T(\lambda)$. Lumping all the other ...
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1answer
22 views
MATLAB: Prepare an RGB image for digit and letter recognition
I need a Matlab function that prepares an image for digit and letter recognition.
What I need now is to convert the original RGB image to a binary image that every pixel in it is white except the ...
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0answers
30 views
Spatial frequency and video frequency of an image
in my lecture notes about image sensors (CCD, precisely) I have read the following statement:
The transfer function $F(\omega)$ of the image sensor is related to its spatial resolution function $F(\...
1
vote
1answer
33 views
Is it okay to interpolate between overlapping areas obtained using a sliding window?
I am using a 50x50 pixel sliding window which moves left to right every pixel so that it covers a whole binary image which is about 2000x2000 pixels. In the window, the ratio value of black to white ...
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vote
3answers
150 views
What does this paragraph mean?
I'm reading this paper about about an algorithm to measure image sharpness, and am confused by these sentences in the 6th paragraph:
It is well known that the attenuation of high-frequency content ...
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0answers
16 views
Standard Deviation of Character Gradients in a Document Image
I have the paper titled "CG-DIQA: No-reference Document Image Quality Assessment Based on Character Gradient". It is all about assessing the quality of the document image based on its blurriness. To ...
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0answers
16 views
What is Maximally Stable Extremal Regions (MSER)?
In the paper , MSER is being defined. Please help me understand what is MSER and how to implement it.
The paper says,
The regions are defined solely by an extremal property of the
intensity ...
0
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1answer
20 views
Comparision between SSIM and MAD Image Quality Assessment Algorithms
I have been working with Most Apparent Distortion(MAD) tool to evaluate the quality of images. I have read a paper that compares SSIM, PSNR, FSIM, etc. with MAD. I am uncertain about some calculations ...
0
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1answer
33 views
Image Processing [closed]
I have an image and I am trying to find its rows and columns.
A = imread('lena.jpg');
nrows = size(A,1)
ncols = size(A,2)
This is 3 dimensional matrix. Output ...
0
votes
1answer
22 views
Regarding the nature of white noise in images
I have just started learning the very basics of noise.
I have come to understand what white noise is in sound samples, but I do not understand the meaning of white noise in images.
In sound samples, ...
0
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2answers
40 views
Average image over $N$ frames with one frame buffer
Can you give some filter that is averaging an image over $N$ samples in a recursive way that only needs one frame buffer?
$\frac{1}{N} \sum_{k=1}^{N} y_{k}(m,n)$
I can only imagine filters that need ...
0
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0answers
21 views
How do you apply DCT steganography on an RGB image?
I am working on a DCT-based steganography program in Python and I found a working model in Github. The program, however, can only encode on one of the RGB channels. Resulting in a discolored image. ...
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0answers
52 views
Maximally Stable Extremal Regions (MSER) Implementation in Document Image Character Patch Identification
My task is to identify character patches within the document image. Consider the image below:
Based from the paper titled "CG-DIQA: No-reference Document Image Quality Assessment Based on ...
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0answers
23 views
Why is my Fourier descriptor not rotation invariant?
I am trying to implement a simple contour based Fourier descriptor to classify some MNIST images. Nothing fancy.
As expected, if I discard the first coefficient, I achieve translation invariance. ...
1
vote
1answer
30 views
Identify if a Specific Edge Pixel Belongs to Horizontal, Vertical or Diagonal Edge Line
I have a code below that identifies the edge of the text image. Input image is:
Output display is:
I want to select random points near the edge border of the text. I was thinking to identify if the ...
0
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1answer
39 views
How is downsampling and low-pass filtering done in MS-SSIM?
I am just studying the Multiscale Strutural Similarity measure for image quality and going through the original paper [1].
I think I understood the basic ides and "regular" structural similarity, but ...
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0answers
10 views
Need to calculate the VARIANCE of GLCM matrix of an image in MATLAB
I have calculated by Matlab the four characteristics of texture derived from the GLCM or co-occurrence matrix (entropy, contrast, correlation, energy) but in what way can the VARIANCE be calculated ...
0
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1answer
39 views
Measure how Straight/Smooth the Borders are Rendered in an Image
I have two images:
I want to measure how straight/smooth the text borders are rendered.
First image is rendered perfectly straight, so it deserves a quality measure ...
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0answers
23 views
Dirty Image Quality Assesment Measure
I was looking for a way to measure how dirty is the document in image processing. Example images below:
a. Dirty Backgrounds
b. Dirty Backgrounds with Text
Can someone give me an initial idea to ...
0
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0answers
72 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 ...
0
votes
1answer
26 views
Modifying sizes and thickness of letters to “embed” an image in text
I am wondering if this is defined, names and possibly solved - suppose I have a grayscale image and about one page worth of text. I would like to attempt to give the text an appearance of an image ...
0
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1answer
46 views
Why we need Laplacian for edge detection?
I am studying some trivial computer vision processing techniques and I came across edge detection algorithms. IMO sharp changes in the gradient are enough indications to detect the edges in an image ...
1
vote
1answer
48 views
How to compute an old style shore line drawing?
I wish to represent a shore line, old-style, as in the following image (city on the left, water on the right):
UPDATE: new image for another example of what I'm after, namely the thin lines (given ...
2
votes
1answer
26 views
Describing a certain quality of an image
Generally I guess Iām asking for a source of image processing terminology.
Specifically here Iām trying to find the word for the quality that would identify the main difference between the Mondriaan ...
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0answers
15 views
Grading Images According to the Noise It Contains
I have collected a lot of dirty blank pages and each image is varied in the noise it contains. How will I grade images according to the noise it contains in terms of amount, and other aspects? What ...
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0answers
13 views
Overlaying A Distorted Text According to its Background
I have several dirty background images, sample image is below:
I want to overlay a text on it but I want the text to be as distorted as the background. Example, if the background is a bit wavy, I ...
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0answers
11 views
Measure that Compares an Actual Old Document from a Synthetic Old Document
I have collected dirty background images, below is the sample:
I have also a collection of an actual image of a dirty document with text on it, just like below:
My problem with my actual image of a ...
0
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0answers
11 views
active contour without edges
i am new to image segmentation.i am studying chanvese ACWE paper1.This is level set equation of chan vese paper ACWE.
Above, Ī¼,Ī½,Ī»1,Ī»2 are real parameters, c1,c2 are constants determined for ...
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1answer
41 views
Comparing spectra from hyperspectral images
I extracted the mean spectra of regions of interests of different tissues from hyperspectral images. How to compare those spectra by the difference of their reflectance and their spectral behavior (...
0
votes
1answer
33 views
Fixing edge/pixel defects in image
I have a large number of images that are supposed to look something like the top part of the image:
Instead, some have defects in them, as in the bottom part of the image. As you can see, there are 2 ...
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0answers
74 views
How to improve interpolation for chroma upsampling (4:2:0 to 4:4:4)?
I am trying to perform the best possible interpolation in order to perform proper chroma upsampling from 4:2:0 YCbCr to 4:4:4 YCbCr. I have implemented the improved interpolation proposed at this ...
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0answers
19 views
Finding Duplicate Pixel/Objects along Image seams
I have a seam of two photos joined by a seam alignment algorithm that on occasion generates duplicated pixels/objects/artifacts on both sides of the seam in the final, aligned photo. The images are ...
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0answers
192 views
What is the definition of the bsd68 dataset?
If I just google "bsd68 dataset", I find this page which allows to download the whole BSD dataset, with all 300 images (potentially 500).
However, I have no idea which of the 100 test images are ...
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vote
2answers
2k 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
1answer
381 views
Generating Kawase Blur Kernels to Approximate a Gaussian Blur on an Image
Is there an algorithm to generate the Kawase Blur Kernels to approximate the actual Gaussian Blur (of a specific kernel size, and if possible, a sigma)?
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0answers
51 views
Randomly Generate Synthetic Noise in an Image Text Document
I'm working on denoising dirty image document. I want to create a dataset wherein synthetic noise will be added to simulate real-world, messy artifacts. Simulated dirt may include coffee stains, faded ...
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0answers
34 views
What does dynamic range values in SSIM image quality technique refers and how to calculate?
http://en.wikipedia.org/wiki/Structural_similarity
Below is java implementation of SSIM.
...
2
votes
2answers
63 views
What are the measurable factors of image sharpness?
I need a way to present data on an essay written about image sharpening algorithm. So I've thought that if I measure a factor of sharpness from image or relative sharpness (between test img and ...
2
votes
1answer
200 views
Estimate Variance of Additive White Gaussian Noise (AWGN) Given Multiple Realizations with Different Mean
Given $ N $ images of the same scene, where each image is corrupted by additive white Gaussian noise of the same variance $ {\sigma}^{2} $. How can $ {\sigma}^{2} $ be estimated?
So we have an Image $...
3
votes
1answer
201 views
Strong (0,0) pixel among an otherwise normal cross correlation peak
I am working on an imagery registration problem via cross-correlation and am seeing a weird phenomena sometimes. First, I am pre-processing each image by subtracting the mean image brightness from ...
