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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2
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1answer
157 views

Obtaining the size of objects from an image

My objective is to be able to obtain the size, in pixels, of objects in images I'm receiving from a camera. I've tried two approaches thus far, both working to some extent, and I'm wondering if there'...
0
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1answer
160 views

convolve to differentiate black and white colors

a figure for instance of size 500*500 has half above part with black and below half white should result in a white line where the white meets the black (something like a single line at line 250 with ...
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2answers
810 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 ...
0
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1answer
223 views

How to detect the maximum resolvable spatial frequency of camera?

I am trying to calculate the minimum line pixel width that can be distinguished from noise as shown in the camera test chart in Figure 1 where the thinner lines on the left are getting more and more ...
0
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2answers
39 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 ...
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0answers
29 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(\...
0
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1answer
25 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 ...
1
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1answer
30 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 ...
0
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1answer
14 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 ...
16
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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.
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3answers
147 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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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://...
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1answer
41 views

What principles to use, in order to create field that will be read by OCR?

I currently have an invoice, where some numbers are written by hand, and I would need to read them automatically. My past experience is that people who write numbers will them write in so many ...
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0answers
15 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
116 views

Algorithm that Fills the White Holes Within the Character Image

I have this degraded image : Using paintbucket tool in Paint.NET Windows application, I fill the character image black. My ...
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 ...
1
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2answers
854 views

Generate a nonuniform illumination (bias field) 2D image

I am creating a nonuniform illumination in MATLAB R2015. The nonuniform illumination (known as bias field) is defined as Nonuniform Illumination (intensity inhomogeneity) which manifests itself as ...
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0answers
15 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 ...
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0answers
45 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 ...
0
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1answer
32 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
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1answer
20 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, ...
3
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1answer
943 views

DCT Steganograhy

I'm trying to implement a simple steganography algorithm (similar to JSteg algorithm) for hiding data in LSB of DCT coefficients in Matlab, and I ran into a problem. a. I apply DCT. b. modify LSB ...
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0answers
18 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. ...
12
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3answers
986 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 ...
-1
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1answer
197 views

Comparing Computation Time of Applying Separable 2D Convolution: 2D Direct Convolution, 2 1D Convolutions, Frequency Domain

Consider filtering square n*n images by square,separable m*m filters. What are the general computation time for the following approaches 1) FFT 2) by 2-D convolution 3) by two 1-D convolutions. (...
0
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1answer
291 views

Brightness equalization between different images

I am dealing with a proprietary whole slide image format from 3DHistech, namely MRXS. This image is produced by scanning a glass slide biopsy. The scanner takes pictures at certain positions which ...
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1answer
337 views

Compression ratio for 4x4 block

Say I have the following 4x4 block: [ 120 121 125 119 120 120 118 117 122 121 117 118 122 122 120 120] If this block is intra coded the ...
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3answers
787 views

How to select the specific frame with object

I am detecting the object from the live camera through feature detection with svm , and it read every frame from camera while predicting which affect its speed , i just want that it should select the ...
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0answers
18 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
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1answer
28 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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2answers
508 views

Segment highly packed nuclei with dotted high intensity signal inside each object

I collected high magnification images on cell nuclei and I need to segment them (red circle in the image). The edges of the nuclei are visible but inside each nuclear object there are bright spots of ...
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4answers
266 views

How to see the amplitude of each frequency?

do you know software that exports spectrograms to images of 500x22000 pixels? all the spectrograms that I know show diffused frequencies and it does not look very good I just want to see the amplitude ...
0
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1answer
31 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 ...
0
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0answers
8 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 ...
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2answers
1k views

Estimating the Variance of Noise Using Median Function Applies on the Gradient of the Image

By investigating the implemented code of an accepted paper, I encounter with following relation to estimate the variance of noise in an image: $$ \sigma = \frac{median (|\nabla^hx-median(\nabla^hx)|)}...
2
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1answer
655 views

The Kernel of the Guided Image Filter

I am trying to understand how to calculate kernel matrix for guided image filter. Following is the formula for kernel calculation. where k is window withing pixels i and j belong i assumed that ...
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 ...
3
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2answers
5k 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 ...
4
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2answers
523 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 ...
0
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3answers
22k views

How to apply a 2D -2D homography matrix to an image?

I have a mini project to do about homography, but I am really a beginner in Matlab. I have calculated the homography matrix easily by taking a set pixels from both images but the problem is how to ...
0
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1answer
1k 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 ...
2
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1answer
25 views

Describing a certain quality of an image

Generally I guess I’m asking for a source of image processing terminology. Specifically here I’m trying to find the word for the quality that would identify the main difference between the Mondriaan ...
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0answers
22 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
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 ...
1
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1answer
86 views

Generating spectrogram for band-pass filtered wav file python

I have some .wav files of heart sounds. I want to apply band-pass filter [20Hx 100 Hz]. Then generating PCG images size of 560x420 pixels and RGB format. How could i do this? Any help will be highly ...
2
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1answer
64 views

Localized Gamma Correction

Question: Is there an algorithm that does (what I would call) "localized" gamma correction? That is, applying different gamma corrections on different parts of an image, using a masking filter or ...
0
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1answer
166 views

Algorithm/Code for finding surface shape of an image?

Is it possible to find the surface shape of an image as mentioned in the reference question ? If I find the unknowns of the equation , then what should be my next step in determining the shape of the ...
0
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1answer
42 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
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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 ...
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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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