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.

91 questions with no upvoted or accepted answers
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487 views

Box filter approximations for oriented gabor filters

I'm currently working on a library to generate synthetic fingerprints using the SFinGe method (by Maltoni, Maio and Cappelli) link :http://biolab.csr.unibo.it/research.asp?organize=Activities&...
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99 views

Perceptually Corresponding Error Map

Is there any better measurement of error between two images than just taking pixel value differences? The problem I am tackling is stitching images containing "sensitive" objects, such as moving ...
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60 views

Combining two images with different resolutions?

I am attempting to combine two radar images, each of which is a 3-dimensional cube with a range dimension, an azimuth angle dimension, and an elevation angle dimension. One image has high azimuth ...
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244 views

How do 2D DCT basis functions interact to produce 8x8 JPEG tiles?

This section is a bit of an intro. If you want to skip directly to where the problem is explicitly outlined, skip to the bottom of this post. Please note that I'm not hip with mathematical lingo, so ...
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499 views

How do piecewise affine transformation work?

How can piecewise affine transform be used to warp an arbitrary collection of input landmark coordinates to a corresponding set of base coordinates? Can anyone give any physical examples, the book I ...
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57 views

Best focus image of stack

I am trying to find the image which has the optimum focus of a focus stack (10 images). I am able to find the best two images by using the minimum gray intensity values but now the problematic part ...
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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'...
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92 views

Classify areas of an image based on color

I have some tree canopy images that I would like to process, but not sure how to get started as image processing is a little outside my area of expertise. Any help would be appreciated. I have tree ...
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68 views

What filters are used in this picture?

What filters are used to get an image like one on the left? I need to find the body pose of a person in a picture.
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82 views

Log LUT applied before bebayering vs applied to RGB

In order to get more detail when encoding the blacks, a log LUT is going to be applied to the pixel values. Like gamma, the logical place to do it in the image processing pipeline is after ...
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875 views

Determine line rate and frame rate of a system

I have as a homework to determine the line rate and frame rate for a system described above: ...
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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(\...
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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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44 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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28 views

How does phase relate to motions in an image?

There is lots of research based on exaggerating motions by decomposing an image into complex sub-bands using pyramid representations such as the complex steerable pyramid and manipulating phase ...
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19 views

Can an untilted perspective of an object be obtained from a 2D image of a tilted object using angular transformations?

I'm trying to make a height estimation algorithm that works in tandem with a bounding box object detector. The object detector can recognise the objects in images taken at pitch/yaw angular offsets. ...
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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 ...
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44 views

sharpness in DCT domain image

How can we calculate the sharpness of Discrete Cosine Transform domain of an image?Is it worthy in image quality assessment?
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367 views

SSIM index: Clearly explained

I am trying to understand the SSIM index to compare two images for similarity, but I am having difficulties understanding how it is done. Therefore, I would like to ask, if someone can explain it ...
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0answers
46 views

Texture detection

I am looking for good methods, preferably parameterless, to detect textured areas in an image. I mean random textures, not regular patterns. The final goal is to discriminate between significant edges ...
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1answer
340 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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0answers
64 views

Image feature extraction for discrimination

I am using linear/quadratic discrimination to guess who is the artist of a painting. All the images are RGB format and I use matlab. I have used both original image and images that are resize to be ...
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0answers
425 views

Filter image in Fourier space imaginary components after ifft (R)

I want to high-pass filter an image in Fourier space. It works but the retransformed image has an imaginary part, what shouldn't be the case http://math.stackexchange.com/questions/867337/how-to-...
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0answers
50 views

Suggestions for inhomogeneous particle segmentation

I need to detect multiple particles of different colors in an image (see example image). In case of very homogeneous particle coating distributions, i.e. all particles look very similar, I can achieve ...
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2k views

Measuring sharpness/contrast for autofocus

For the implementation of an auto-focus for the raspberry cam I need some measure of image sharpness. I used the following sample picture: The first approach was to compute the shannon entropy of the ...
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0answers
79 views

How to classify images based on the amount of colors in the image?

I have a problem where all images have the same object; however, these objects can either have number_of_colors<=3 OR number_of_colors>3 and images are not labeled. My attempt starts by ...
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0answers
130 views

Image Subtraction using Pre-bayer data (.pgm)

Not sure if this is the best stack exchange but I'll give it a shot. I am performing background subtraction to collect Electroluminescent emission (i.e image w/ emission - image w/o emission = ...
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151 views

Equivalent of the Shepp-Logan phantom for video denoising

The Shepp-Logan phantom is a standard test image used in reconstruction algorithms as well as image denoising. Does an equivalent image sequence exist for testing video denoising algorithms? I know ...
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0answers
2k views

how to get segmented OPTIC DISC from retinal image?

i have been segmented some image of retina. but the result is not good as i hope. for one image i can get good segmentation, like this image my code is from some reference in internet, in below i ...
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0answers
71 views

Affine Parameter Optimization using simulated annealing

I am working on a project to compare images in the database. I use color and gradient orientation as features of the image and these features are not rotation invariance, therefore to compare well I ...
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504 views

Impact of different padding schemes in Frequency domain image filtering

I understand, that image padding is necessary in order to prevent wrap-around effects due to circular convolution. My set of questions are related to different padding schemes. Zero Padding is easy ...
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79 views

Image Compression (JPEG) - Show the Effect of Number of Coefficients on Quality

write an m-file that will take the"cameraman" and produce a image quality or difference matrix for spectral selection method.The image properties are a sfollowings: For spectral selection: image1:DC ...
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57 views

The relationship between zero level set and thickness information

I have one problem that need you help. I am try to find the relationship between active contour and thickness information. For defination of thickness we can find at thickness measuring and active ...
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0answers
9 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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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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120 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 ...
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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 ...
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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. ...
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46 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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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. ...
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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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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 ...
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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 ...
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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 ...
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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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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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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 ...
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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, μ,ν,λ1,λ2 are real parameters, c1,c2 are constants determined for ...
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55 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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16 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 ...