Questions tagged [image-processing]
The image-processing tag has no usage guidance.
158
questions
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44 views
35 mm equivalent focal length but with a different aspect ratio
I am doing some image processing and am a little bit confused about reporting a 35 mm equivalent focal length. I am working with a 640x360 image which has an aspect ratio of 1.7777. A 35 mm film is 36 ...
3
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1answer
56 views
Compute Shader shared average value
Short Question:
How can i integrate a buffer variable in a compute shader over each pixel i.e. how can i ensure memory coherence in such a case?
Long Question:
I've written a deferred renderer with ...
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27 views
Efficient method of mapping any RGB tuple onto a list of RGB indices, is using some kind of partition plane viable?
Suppose we want to convert an RGB image into a paletted image. As an example, we may have a 1024x1024 image, and we want to map it onto 512 unique colors. All the colors are RGB. This is a problem of ...
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1answer
35 views
Difference between Gray-Level and Gray-Scale?
What's the difference between the terms Gray-Level & Gray-Scale ?
I think that Gray-Level refers to the matrix of light-intensities of the Black-White digital image itself whilst Gray-Scale refers ...
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47 views
How to generate a thumbnails index file?
Given a folder full of pictures, how can I generate a thumbnail index file for them? Basically I want to generate a single picture that has thumbnails of everything inside the folder, with a file name ...
3
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1answer
54 views
What's the word for "how noticeable a particular part or pixel of an image is to a human"?
I remember hearing about an algorithm to calculate some property of each pixel of an image which represents how noticeable that pixel is to a human, and so how likely they are to notice if that pixel ...
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1answer
182 views
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25 views
Filling pixels under or above some function
Seems like a simple problem, but I just cant wrap my head around it.
I have a config file in which I declare a few functions. It looks like this:
...
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39 views
Building a higher-res detailed image from a video
I'd like to know if the following technology already exists, and if not, how feasible it would be to create something like this:
I came up with an idea for creating a higher-res image that is put ...
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14 views
Overlaying a specifc color with LinearLight or Multiply -> reverse color maths
We have source images in gray or white color and want to overlay a specific color via imagemagick's composite function.
Currently we generate a solid color area and use composite-overlay to overlay ...
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0answers
27 views
Normalized image for shape from shading
Im going over this paper by Vogel A Direct Numerical Approach to Perspective Shape-from-Shading. I have a problem in the way they define the normalized image brightness I(x) as:
I(x) = E(x)/sigma
...
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34 views
Pinhole Projection & Spheres [duplicate]
Would someone be able to explain why a sphere when projected with the pinhole projection model has its projected 2D image be an ellipsis. IN particular when the sphere is not directly in front of the ...
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32 views
How to extrapolate an object from a photo taken with an iPhone
First off, this may not be the right group, however, it is the closest one I can think of.
I took a few pictures of a computer panel at a known distance, but the angle to a corner would require the ...
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1answer
45 views
How is the multiplication in Gaussian Blur implemented
I have a question regarding how the Gaussian blur works. A pixel consists on the combination of 3 colors: R,G and B. I have read that the Gaussian kernel is multiplied by the input image
by placing ...
0
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1answer
110 views
Calculate the position and rotation of a quad in 3d space given a 2d projection of that quad from a camera
I am trying to build a VR tracking system with a laptop webcam, and I have succeeded in identifying, and tracking paper markers I put in front of my webcam. For context I am using OpenCV with the ...
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29 views
How to render a rotated raster image with lesser aliasing
I am wondering about techniques for rendering a rotated and or scaled raster image. Currently I use the following algorithm
Render everything at double resolution and store the result in ...
1
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1answer
62 views
How to pass only the needed portion of the data calculated in a fragment shader to another fragment shader?
I have an image and I want to draw an arbitrary number of objects on that image. The center coordinates of those objects are calculated inside a fragment shader after series of image processing ...
1
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2answers
36 views
splitting hue & saturating and leaving value behind
In an HSV model, the Hue is the color model. So when we split the image or remove H, should we get an image without rgb colors?
Similarly, saturation is the gray shade. I read that images become more ...
1
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1answer
251 views
How to calculate spatial frequency of an image just in one direction?
FFT spectra is not what is needed; what I need is a histogram showing which frequencies are there in image in horizontal direction, and which one is dominant
Such spatial frequency is usually known ...
2
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3answers
79 views
How to paint onto 3d models
I have searched this topic for very long time and have found basically no information on it.
If we have a 3d model with a uv layout. What is the basic technique for 3d painting on said model with a ...
0
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3answers
119 views
How to remove background text from an image file
I have this image below, I want to get rid of the text 'MSAR IDs' that is in the background. I am extracting the numbers from the image with OCR, the numbers that have a white background get extracted ...
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28 views
Do scanners and scanning software compensate and enhance blurry sources?
I received a pdf from a client containing several invoices. Upon further inspecting, some lines on the invoice seem digitally produced. When I tried selecting the page, copying it then pasting it on ...
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44 views
Are there algorithms besides Canny edge detection that can create consistent width edges?
Sobel edge detection is pretty much the quintessential way to get edges out of an image. It however suffers from certain quirks.
One example is, because it's gradient, based certain surfaces exhibit ...
2
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1answer
41 views
Interpreting Image Processing Math Equation
I am reading "Image Processing and Analysis" by Chan and Shen, c 2005 SIAM. They introduce some notation I'm not 100% sure how to interpret:
$$ u_0(x)=u(x)+n(x), x=(x_1,x_2) \in \Omega $$
They ...
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0answers
47 views
What modern C++ Unit Testing Framework do you use for highly parallel image, 3D and higher dimensional matrix processing workloads? [closed]
Most of the existing open-source libraries such as OpenCV, Tensorflow, and Pytorch use Google Test. I would like to know about strong alternative testing frameworks that thrive under a similar ...
1
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0answers
39 views
HSI color space and RGB color space relationship in Steganography
I need to embed text in an image, research papers say HSI produces better mse and psnr therefore are better for steganography. I have RGB values(69,223,90) and its corresponding HSI is (127.223,0.458 ,...
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47 views
What fast algorithms can generate not-realistic but quite handsome animated landscapes?
I was looking for algorithms that quickly compute quite nice realistic, or not realistic, animated landscapes, in video format ("animated" = the camera moves, or the water is animated, etc.) But all I ...
1
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1answer
61 views
Given a background image B and a composie image of A OVER B, can we somehow recover image A?
I often find myself in the situation where I have some old image where I composed a translucent overlay on top of a background, but then lost (or more likely discarded) the overlay. I still have pre-...
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0answers
129 views
Visualize the variance of an image
Let $h_j$ denote the image reconstruction filter of pixel $j$.
I'm estimating the color value $$I_j=\int h_jf\:{\rm d}\mu$$ of the $j$th pixel (see [Veach, Section 8.2]) by an asymptotically ...
2
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1answer
75 views
Controlling "zoom" and "position" of a cubemap in shaders
I am trying to mimic reflections in image composition using shaders.
I have gotten this far:
In this image the floor is "reflecting" the back wall, however the reflection is uncanny because the ...
3
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0answers
117 views
Upscaling screenshots with subpixel rendered text
Upscaling a screenshot with subpixel antialiased text produces unpleasant color fringes, e.g. why does black text have orange and blue pixels This is especially annoying when trying to show an ...
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0answers
33 views
Extract object from image and apply it to different image
SHORT BACKGROUND:
I am developing a neural network based model to differentiate benign and malignant ovarian tumors. I am working with transvaginal ultrasound images, some of which contains yellow ...
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35 views
Convolution of multiple gaussian filters with different sizes
What is the size of the final filter after implement convolution of multiple gaussian filters with different sizes?
1
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1answer
194 views
Extracting information from EXR Files
I am relatively new to computer vision and image processing. I have a single EXR file with 7 channels: 1-3 give me the RGB values, 4-6 give me the surface normals coded as RGB values and 7th channel ...
1
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1answer
548 views
How do you add text dynamically to an image and export it?
Apologize for crossposting, but I posted this in Stack Overflow and thought it might be a better post here.
Recently, Spotify released their 2019 Spotify wrapped web application, which is essentially ...
1
vote
1answer
62 views
What kind of denoising must follow locally adaptive binarization?
I am experimenting with local (adaptive) grey threshold for the binarization of B&W photographs of yellowed manuscripts:
I got adaptive thresholding working in both scikit-image and cv2. In both ...
0
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1answer
247 views
How RGB images are formed when normalized between 0 and 1
There is a popular technique of normalising images by dividing each pixel with 255 so that it comes in the range of 0 and 1.
But, then how the same colours are formed when we normalize images.
for ...
3
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2answers
564 views
What does texture resolve mean?
In the context of render targets or textures, what does "resolve" mean?
For example: To resolve a color texture.
From my understanding, it seems to mean, "copy but process/convert at the same time", ...
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0answers
37 views
Fuse 3D-Points in Bundle Adjustment? [closed]
(Crossposting from here: https://softwareengineering.stackexchange.com/questions/399331/fuse-3d-points-in-bundel-adjustment)
I'm actually implementing my own Pose-Estimation/- and -Refinement ...
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1answer
84 views
How to create static alpha masks of an image
I have an image of following type-
I want to create mask of the following type where the inside area is white and rest of it is black. How to do it?
1
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1answer
114 views
Artificially increase the region of interest of an image
I am solving an image segmentation problem. To increase the accuracy of the model, I came across the following preprocessing step-
First, the set of pixels of the exterior border of the ROI is de-
...
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2answers
101 views
Is there way for polygon decomposition by thickness?
Here is an example
dots representing coordinates of pixels
added more representative example
added real example
added main problem
1
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3answers
575 views
Blurring image with RGB values without convolving it with a kernel
I'm using an app for face redaction that doesn't allow access to the source code but only allows me to pass pixel values for red, green and blue channel upon which it creates a matrix with the same ...
2
votes
1answer
101 views
Estimating the position of vertexes in a 3D model
Introduction to my project:
We are machine learning scientists and working on a biomedical system for tracking tongue for speech pathology using a technology called EMA (Electromagnetic ...
0
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2answers
132 views
How RGB images are formed
I have a noob level question about RGB images-
Pixels in RGB images are in the range of (0-255), so technically each channel ranges from 0(black) to 1(white), then why we say that each image has a Red,...
0
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1answer
137 views
Want to study computer graphics
I want to study computer graphics but I don't have a strong foundation in mathematics. I am doing a computer science degree that doesn't cover computer vision, image processing or computer graphics, ...
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0answers
52 views
Deskewing and Cropping Scans using ImageMagick
Attempting to deskew and crop scans of a CD booklet using ImageMagick.
Here's one image which I've been using as an example on which to build my one-liner - https://mega.nz/#!jIQD3aqC!PbjG4_Xaq-...
2
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1answer
445 views
Downscaling texture via mipmap [DirectX 11]
I am implementing a post-processing effect in my DirectX 11 pet renderer. The post-processing pass is implemented by rendering a full-screen quad covered with texture containing original rendered ...
3
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0answers
75 views
How to separate, modulate, and reassemble spatial frequencies?
Background
I am trying to create a node in Blender that would allow me to do what you would do with an audio equalizer but on the spatial frequencies of an image: A sort of panel with eight ...
3
votes
1answer
91 views
Origin of blurring and colour distortion in monochrome diagrams
I am analysing a large number of PDF files from scientific articles, all of which contain images which (I think) were originally monochrome ( black/white).
The images have been extracted with Apache ...
