What's the deal with Deno? We talk with a major contributor to find out. Listen now.

# 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.

465 questions
Filter by
Sorted by
Tagged with
495 views

### Confirming what a compression ratio is

I have looked at various sources, but still have not been able to answer the question: what is compression ratio? I have come to the understanding that this is the definitive answer: compression ...
88 views

### Using morphological operations for color images processing

Have you ever seen any articles about using morphological-like technique for denoising color images?
176 views

### Quadtree decomposition of Discrete Wavelet Transform using bio4.4/CDF wavelet

My problem is pretty basic but fundamental. It relates to the way discrete wavelet transform behaves for biorothognal 4.4 or CDF wavelets. When using most wavelets (e.g., CDF 9/7 or bio4.4 or ...
752 views

### Is there a difference between Image Alignment and Stereo Rectification for stereo correspondence or matching?

As far as I know, Image alignment just finds the best fit given two images of the same scene. Whereas Image rectification, with regards to stereo vision, warps the images so that the epipolar lines ...
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. ...
207 views

### Super- resolution: Warp Matrix

The super resolution model is as such: Y_k = DHFX + N , where Y_k is one of the N measured low resolution image, D is the Decimation Matrix, H is the blur matrix , F is the warp matrix, N is the noise ...
116 views

### In filtered back-projection, what does the $z$-axis in the reconstructed cross-sections represent?

The MATLAB code below is used for filtered backprojection (for $x$-rays). In this example program, it reconstructs an image of a simulated checker board, generated by the program. It uses Fourier ...
342 views

### How to predict next image in a sequence, or predict the deblurring of an image?

I have 3 versions of an image at lower resolutions - 480p, 720p, and 1080p. Is it possible to use those 3 images to predict the next highest resolution image (the 4k image)? My first guess was that ...
281 views

### How to generate sinusoidal images that shift over time

I try to generate an image using this code. ...
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 ...
186 views

### Are the HOG features of the images good enough to do image classification alone? Why are their variances low?

I've also asked this question here:https://cs.stackexchange.com/questions/77884/are-the-hog-features-of-the-images-good-enough-to-do-image-classification-alone I've been working on classifying human ...
301 views

### How to remove weak edges in a binary photo?

See attached photos for reference. I tried watershedding, it breaks apart the main body and doesnt even touch the part I want disconnected! morphology is no good, the holes in the main body easily ...
70 views

### What is the optimal way to select by color?

I need to select all pixels in a image that are similar in color to a given one. My current approach is to get the hsv values for this pixel and calculate the distance to each pixel in the image ...
2k views

### How to make color balance of photoshop using opencv

I want to make the same thing programmatically like Color balance in Photoshop , like in below image if we have same bar ...
923 views

### pixels in the same image are correlated but how can I visualize it?

I am new in image processing.I know that pixels in the same image are correlated with each other but I don't know how can I draw the relationship b/w these pixels in the form of graph?.
822 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 ...
456 views

### How do I properly do gamut mapping for an image?

I asked this question earlier. To summarize, dithering an image with a specific palette was causing the image to look smeared and very discolored. Thanks to Olli Niemitalo, I found out my issue was ...
639 views

### Simple way to replicate bloom (glow) effect in image using Matlab?

I have some simulated images of light bulbs in Matlab. What I want to do is replicate the bloom (glow) effect on these images. The degree of the effect (i.e. how much the light bulbs bloom) should be ...
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 ...
576 views

### Uncorrelated and zero mean image noise

Consider a noisy image g(x,y) formed by the addition of noise n(x,y) to an original image ...
429 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-...
1k views

### Easy PSNR and SSIM calculation? [closed]

I searched around the internet for a ready implementation/library for estimating 2 images by PSNR and SSIM, but found no real implementations for either. Are there really none or am I maybe missing ...
1k views

### How does Jpeg encoding affect the final file size of 24BPP RGB and 8BPP grayscale image?

The reason I'd like to know this is because of a file size problem. I am trying to reduce an image's file size from converting it from TIFF to JPEG. A user challenge me that he notice a RGB TIFF image ...
289 views

### How to use Principal component Analysis(PCA) to extract feature from images [closed]

How can use principal component Analysis to extract feature from image that is been acquired by the camera?
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, ...
43 views

### Looking for a file format for lane detection

I am trying to extract lane boundary lines from two recorded video cameras on the sides of the vehicle. I would ultimately like to calculate lane position from those boundaries. My thought process is:...
36 views

### Filter an image based on subset

I try to filter an image using this equation: $$I_f(x_j, y_k, t)=\sum_{p=-q}^q\sum_{r=-q}^q I(x_{j+p}, x_{k+r}, t)$$ where $I$ is the original image in grayscale, $I_f$ is the filtered image and \$...
309 views

### Parallel Processing Gigapixel Images

Parallel programming is often used to accelerate image processing methods (e.g. Eklund et al., 2013); however, there doesn't appear to be the same level of discussion about using parallel processing ...
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 ...
3k views

### Power spectrum of 2D image: result interpretation

Let's say I have an image, which is NxN pixels in size. If I calculate the fourier power spectrum of this image, I get NxN values, with the highest distinguishable frequency at +- N/2 in each ...
153 views

### How many 8x8 JPEGs exist with distinct DCT given a quality level?

For a given quality of image (or quality of compression), Multiple 8x8 JPEG images can have the same DCT (Discrete cosine transform) matrix, for a given quality of JPEG compression. I want to find the ...
976 views

### Python: How to calculate image perimeter orientation histogram?

I would like to find the perimeter orientation histogram of an object inside an image. The object is returned into an array but I don`t know how to find the orientation of its perimeter. I think the ...
8k views

### How to verify if two images have the same object/content?

I am truly new to computer vision field, but it is fascinating me! I have now a challenge in my hands and I am seeking for mentors/advisers to give me some follow up. My project is: From a picture of ...
43 views

### Image Geometry Terms

I getting confused over some basics of image geometry terms due to different definitions, implementations and different outputs in the internet, here is an example. The terms are: Image derivative ...
192 views

### Whether Poisson noise will be dominant source of noise in low light conditions? [closed]

I have one paper saying that that the Poisson noise will be dominant source of noise in low light conditions and the other one says the opposite way(Poisson noise will be dominant except in low light ...
84 views

### 'imread' function in MATLAB gives image data.what this image data is?is that intensity of pixels?and how MATLAB computes this data? [closed]

i checked imread function code but couldnt understand how it is calculating the data from given image.Please explain.
379 views

### Measuring distance of periodic structure in biological sample with FFT in MATLAB

I have pictures, taken with a microscope, of biological samples that exhibit a periodic pattern. Previously, I have used ImageJ to manually rotate the image perpendicular to the pattern and plot its ...
1k views

### Decompose video frames into slices

I am working on a video motion feature implementation. I am implementing a work in a research paper. What I want to implement is this: The frames contained in a video clip can be thought of as a ...
238 views

### How can I get the uncertainties for peaks on an image?

When pick the peak points on an image, e.g. the matrix made by peak in matlab as this one, I can use max to get the index of ...
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 ...
364 views

### How to apply dictionary learning to several images?

I'm implementing a dictionary learning algorithm for doing sparse coding on images and I have a problem how to learn a dictionary corresponding to several iamges. Letās say X is the data matrix. If I ...
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 ...
7k views

### Radon Transform Implementation In Matlab

I know MATLAB has a built in Radon function, but I am working on implementing the radon transform in order to perform filtered back projection. As I started, my idea was multiple nested for loops for ...
496 views

### Which image for DoG filter?

I am studying computer vision and have some trouble with difference of Gaussian filter. We apply Gaussian filters with different values of sigma on original image then subtracting from them. However,...
257 views

### what is the difference among noise,blurring and contrast? [closed]

I want to know the following what is the difference among noise,blurring and contrast ?
104 views

### Contrast Enhancement for subjects under Flash

For a machine vision application, we take short duration (50uSec) monochrome pictures with IR flash. The images we get are decent quality however the light color subjects (light blue, light green, ...
2k views

### Image compression using SVD in MATLAB

I have to compress an image using SVD. I did a few things, but all of them produced a black & white image. However, the output must be RGB. How can I compress an image without changing its ...
180 views

### Wavelet image denoising: dual-tree versus double-density

What is the main difference between the dual-tree DWT and the double density DWT image denoising techniques? How does the combination of them improve the quality of the denoised image?
205 views

### Estimation of CCD/CMOS sensor noise

I would like to know what is the basic procedure to estimate the noise level of a CCD/CMOS sensor from an image/sequence of images acquired. I am going to use MATLAB to perform this operation. What I ...