Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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66 views

Determining Parameters of S Function for Image Global Contrast Enhancement

I know that S-function (membership function from fuzzy set theory) is a commonly used function for image enhancement. I am reading a paper titled - A Novel Fuzzy Image Enhancement Using S-Shaped ...
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3answers
40 views

Does decoding jpeg images uncompresses them?

I train a convolutional neural network on compressed jpeg images. I noticed that my code takes pretty much the same amount of space in memory whether I use high quality jpeg images or the same jpeg ...
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1answer
12 views

Different type of padding in image?

I want to implement a gradient operator on an image in Matlab. Should I have to pad the image before its implementation? How do I decide which padding to use e.g. whether to use zero-padding or ...
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20 views

Removing the effects of camera motion in a video

I have frames of a video consisting of both a moving camera(translation, rotation, zooming in and out) as well as moving objects. I need to recover only the trajectory of objects which means I need to ...
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1answer
55 views

Zone Plate Reconstruction

I am trying to reconstruct the Zone Plate image and am struggling to remove the last remaining aliasing. ShaderToy: https://www.shadertoy.com/view/wdGGWK In the shader above you can see that I am ...
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0answers
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Significance of outer product in structure tensor / second moment matrix

How does one interpret the outer product $\mathbf{M} = \nabla I \otimes \nabla I = \begin{bmatrix}\left(\frac{\partial I}{\partial x}(x)\right)^2 & \frac{\partial I}{\partial x}(x) \cdot \frac{\...
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2answers
2k views

JPEG DCT padding

Since the JPEG DCT block used is 8x8, how does the method deal with images with dimensions that are not multiples of 8? What kind of padding does it use? How are the 8x8 blocks of the image chosen?
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11 views

Dataset suggestion: video dataset with accurate depth and pose info

Please suggest some datasets (can be synthetic, like rendered in blender or so) which have video frames (30fps preferred) with accurate ground truth depth maps and pose (rotation and translation for ...
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9 views

Where to place origin when warping an image using 3D rotation and translation?

Suppose, I've two images taken by a camera at two different locations. The two locations are related by a Rotation and Translation. So, points $X1$ in first frame will be at $M \cdot X1$ where $$ M = \...
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1answer
24 views

CT Slices to Planar XRay

I have axial slices of chest CT scans. Now, I want to use all these slices to construct a planar structure like an X-ray with a coronal view (Posterior to Anterior or Anterior to Posterior view). I ...
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1answer
107 views

Detect valve position without colors

I can't find a solution for my problem and I need your help. I have to create an application to detect if a valve is open or close like this : https://www.youtube.com/watch?v=VY92fqmSdfA Some ...
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3answers
69 views

Reversing the Order of Operators for Edge Detection?

Usually, for edge detection, we perform smoothing and then pass it through difference filter. What if application of difference filter happens first and then smoothing. How the math behind the same ...
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1answer
33 views

How does DCT decorrelate images?

I've read in multiple places that DCT decorrelates Toeplitz matrices and images usually have Toeplitz structure. Can you explain with an example how DCT decorrelates a Toeplitz matrix? Example for DFT:...
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1answer
28 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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1answer
3k views

How to understand the de-correlation property of DCT? What does de-correlation mean?

Here are three problems that I can't understand: Usually what does de-correlation mean in image-processing? What's the benefit of de-correlation when it comes to image splicing? Is there some ...
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2answers
68 views

1D DCT matlab code

I was writing MATLAB code to compute 1D DCT of sample y. On computing DCT for y=[0,1,2], code generates coefficient ...
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1answer
25 views

Intuition about tag pose estimation accuracy

I have some difficulties to have a correct intuition about expected pose accuracy when dealing with planar pose estimation (e.g. pose estimation from AprilTag detection) and perspective camera model. ...
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4answers
13k views

Best way to remove unwanted region from image

I am finding the techniques to remove unwanted regions (small dots) from image. I have an image that includes object and some unwanted region (small dots- see first image). I want to remove it. Hence, ...
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2answers
40 views

How Does Color Conversion and Downsampling work When JPEG compressing a grayscale image?

For color images I know you have to convert to YCbCr format, and then for downsampling is based on the fact that human beings see differences in Y more than differences in Cb or Cr. How do I do these ...
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1answer
13 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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1answer
30 views

What Is an Oriented Gaussian Second Derivative Filter

In the paper: Detecting and Localizing Edges Composed of Steps, Peaks and Roofs, the authors refer to an image filter as an oriented second-derivative Gaussian filter. I'm trying to figure out what ...
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0answers
83 views

Converting very short “motionless” video frames to single, better-resolved, images

I made a mistake with my newly bought compact camera, before a trip to Japan. Instead of taking single pictures, I ended up with a few short "MP4" video files (1 second, 2-3 frames). I could ...
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1answer
34 views

linear-expansion filter for image (2D array)

I am working in python analyzing 2D arrays and I am looking for a filter or some other routine that would provide a linear expansion of an region boundaries in a 2D array with binary regions (i.e. a ...
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2answers
54 views

What does it mean to rotate an image by 0.1 degrees?

In the old Tangent Prop paper (you don't need to know this paper), the tangent vector of the rotation transformation (think of this as a vector-valued function) at some input image is approximated by (...
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2answers
21 views

MRI K-space to image: why track frequencies in two dimensions?

While trying to better understand how an MRI goes from k-space to an image, I came across this wonderful website that explains how you would represent an image as a collection of rows of pixels where ...
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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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1answer
1k views

How can I detect pipeline cracks using OpenCV and Python?

I have developed a robot that captures images of the pipeline interior as it moves. The requirement was to be able to detect cracks inside. So far i tried several OpenCV codes that find the crack ...
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3answers
7k views

Count objects in the image

How an algorithm can be developed to count numbers and bolts in the image below.
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2answers
761 views

Gaussian pyramid: why needs the image to be downsampled

In the context of a gaussian pyramid, why is the image downsampled separately although the numbers of pixels are decreased through smoothing already? In my understanding, the number of pixels will ...
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2answers
32 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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3answers
146 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
21 views

What is Bottom-Hat transformation?

I am reading the Digital Image Processing book by Gonzalez and i can't seem to understand Bottom-hat transformation. Can anyone explain it to me in easy terms?
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1answer
28 views

Selecting a Digital Signal Processor for a Specific Image Sensor

I am working on developing a camera and I am trying to select hardware for the camera. I believe that I may need a digital signal processor to compress image data before it is transmitted to a ...
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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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1answer
38 views

Detect lines transitioning to blobs in images

I have the following images (in high resolution, uncompressed). When the process starts, the left image is displayed and it ends something similar to the right image. The first image shows labyrinth-...
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2answers
586 views

CLAHE - Redistributing excess pixels among histogram bins

In order to clip an image's histogram to a maximum value, according to the CLAHE algorithm, the excess pixels (above the clip limit) will be distributed equally among all the histogram bins (While ...
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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
111 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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2answers
58 views

Binary image? Only black and white? [closed]

By name, a binary image is one that has two levels. But is it essential that those two colors are black and white? Or any other combination also allowed as shown in attached snap. Snap is output image,...
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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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1answer
17 views

Noise problem when transforming and quantizing difference between images

I have a program which does forward and inverse DCT and quantization and dequantization using JPEG matrix. If I apply it to a single image it works fine, but if I try to apply it to a difference ...
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1answer
16 views

Bilinear Interpolation on A Subsection Of An Image

Is it possible to do bilinear interpolation on each 8 by 8 block of an image one at a time until you cover the entire image rather than doing it on the entire image? What are the consequences of this?
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34 views

What is the gradient of fft?

I have a time-series of length N generated by the following equation: ...
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0answers
23 views

Compressing sparse vectors based on compressive sensing

I have a sparse vector $x$ of size $N$x$1$ which is sparse with number of non-zeros values are $m$, it means $m$ out of $N$ values are non-zeros, the non-zeros locations are distributed randomly. ...
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0answers
21 views

security in biometrics

I read the following in one of the research papers: Cancelable biometrics using random projections can be implemented by multiplying a random matrix with a feature vector. The result is a cancelable ...
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1answer
264 views

Image watermarking in wavelet domain (data hiding in images)

I am working and researching on Image watermarking/steganography and I'm stuck at a point and want to know which technique is better in image processing for data hiding. Bit Plane Complexity ...
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2answers
846 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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1answer
22 views

What happens when you wrap a 3x3 kernel at the corners of an image?

I am puzzled by what actually happens when you process border cases when applying an image filter. For instance if I apply a 3x3 Gaussian kernel to the top left pixel[0][0], the remaining pixels that ...
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0answers
12 views

Computing White Speckle Metric in a Document Image

The paper 'Metric-based No-reference Quality Assessment of Heterogeneous Document Images', discusses about measuring the quality of characters in a document image. I'm having difficulty to understand ...

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