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Questions tagged [image-processing]

The tag has no usage guidance.

4
votes
1answer
421 views

How can I remove aliasing in an image without introducing blur?

I am trying to reduce aliasing in an image using some filters. I tried the Gaussian variant of filters to remove the said high frequency patterns in the image, but I feel it's a bit too much of a blur....
1
vote
0answers
107 views

Finding Segments in Continuous line

I'm trying to break a continuous line segment into multiple, straight segments. I've tried using the Hough transform but have found it unreliable for getting the line segments I'm looking for and ...
7
votes
1answer
619 views

Seamless Textures

I understand how an artist would make seamless textures by hand, but how can a computer program automate that process? Software like PixPlant is capable of doing this, but I don't understand how it ...
5
votes
0answers
128 views

CrazyBump Shape Recognition

I've recently been using CrazyBump, and I think I'm starting to understand how it works. But I'm confused about what it calls Shape Recognition. According to this website, that feature attempts to add ...
7
votes
2answers
559 views

Algorithms to Remove High Frequency Noise from Path Tracing

I have been working on my own renderer for a while, and I'm wondering if there's any way to remove the Monte Carlo noise from the rendered image, besides waiting for a long time for it to converge? ...
2
votes
0answers
351 views

how to overcome tracking jitter

I'm working with a object tracking project. Steps: Preprocessing the image and achieve some candidates regions of interest. For each region, test if it is the target by ORB/BF. After the target ...
4
votes
0answers
84 views

Recreating a font from a low-quality printout

I have a JPEG file with a 200 dpi scan of a sample printout from a badly maintained old drum printer. I was able to segment it and to collect all instances of each letter together, for example I ...
6
votes
2answers
870 views

Pixel dispersion (dissolving) algorithms

This YouTube video of a flip-dot display (physical b/w pixels) shows the reverse of an effect that might be called dissolve or dispersion, i.e. a text emerges from noise by pixels moving in to form ...
4
votes
1answer
113 views

Image regeneration with nearest neighbor search

So what I would like to achieve is this: User submits Image 1 - this image is then broken down into X by X sized blocks User submits Image 2 - then the program/algorithm takes all the blocks ...
3
votes
1answer
75 views

What kind of image processing was used in the Facebook “Celebrate Pride” filter?

I am trying to recreate a filter that Facebook released back in 2015 when gay marriage was legalized in the US. Unfortunately, that filter no longer works/exists so people are left with only knockoff ...
1
vote
0answers
152 views

Octave matrix to image pixels too small (do not have 1 pixel per integer)

I am working on a project which plots points over a checkerboard (representing seats for people). I would like each pixel in the image to represent each integer matrix entry. After updating my ...
1
vote
1answer
102 views

How to generate a 2d histogram?

I'm playing around with volume rendering and looking into multi dimensional transfer functions. I keep seeing images like this for 2d transfer functions: I've read numerous papers and articles but ...
1
vote
2answers
117 views

How to count aspect ratio of an image when you have dimensions?

What formula is for counting aspect ratio of the image as in this site: Aspect ratio calculator (ARC) | NinjaUnits For example: ...
5
votes
2answers
187 views

reducing image size increases file size?

When I download this image: then its total size is 341,0 kB. The image has a width of 2880 pixels and height of 1100 pixel and 1 X/Y resolution pixel/in. I opened the image with gimp and pressed ...
1
vote
1answer
152 views

How to count DPI of an image (challenge)?

a) I have used an online service where you can upload an image. b) Afterwards, you can select a print size and it gives you information on what is actual DPI based on that print size. c) When it ...
4
votes
2answers
493 views

How linear interpolation works between mipmaps?

Nearest interpolation between 2 texels mean to take the texel whose center is nearest to a given coordinate to draw or, in other words, the texel the coordinate is matching. Linear interpolation ...
1
vote
1answer
700 views

Why thumbnail shows just another pic?

Download this picture and see it as a thumbnail, like in whatsapp or your phone gallery and you'll find that it shows another picture in the thumbnail. If you can't see the thumbnail: You can simply ...
1
vote
0answers
114 views

image warping, given the rotations/translations

in OpenCV there is functions to warp any 2D image using a homography matrix (3x3), e.g. cv2.warpPerspective. These matrices are generally constructed using point ...
4
votes
2answers
478 views

How to perform an image normalization after for example adding a constant to it?

I had some magical tasks to do on my lessons. I had to write an app which performs some operations: basic (adding, subtracting, multiplying a constant and a second image), geometric, filtering, ...
1
vote
2answers
251 views

Explanation of a the transparency of an .EXR file

Simply put, what does the transparency data of an EXR file represent?
5
votes
2answers
114 views

Downscaling by skipping rows and columns – any example images?

I'm about to implement downscaling on a microcontroller. Source resolution is e.g. 720x576 (the 576i PAL resolution, other one possible: 480i, NTSC resolution), destination is 32x16. The goal is to ...
3
votes
1answer
176 views

Improved Laplacian smoothing of noisy surface meshes

I have a question regarding Laplacian Smoothing of meshes and in particular the paper "Improved Laplacian smoothing of noisy surface meshes" by J. Vollmer in the early 2000's. What is the reason for ...
1
vote
0answers
28 views

Place images relative to each other based on where they were shot [closed]

Suppose I take multiple 360 photos of a room from various locations but from the same height, how can I place them relative to each other? Ex. 1 - x - 2 x - 3 - x 4 - 5 - x If I shot the photos at ...
1
vote
0answers
62 views

Feature extractions from an image to produce a fingerprint [closed]

Given an image - such as a simple JPEG of a person or a landscape - is it possible to produce an algorithm that extracts certain visual features from the input image to produce a unique fingerprints ...
11
votes
0answers
237 views

Why does increasing simplex noise dimension wash it out?

I just tried using this approach to create a tiling 2d simplex noise function with Gustavson's java implementation. The result tiled, but the texture seemed muddy / washed out. I decided to compare ...
4
votes
1answer
190 views

What graphics techniques can be used to simulate a color nebula effect?

I've been playing around with more advanced graphics these days (beyond the basic 2D UI and image effects that the iOS platform offers), and I'm wanting to implement a visual effect similar to how iOS'...
1
vote
1answer
56 views

Compression-friendly PNG files

How to create PNG files optimized for being compression-friendly? I.e. would it help if image is created (mostly) from 8x8 unicolor blocks?
1
vote
0answers
163 views

Feature detection for embedded platform OpenCV

I'm trying to do object recognition in an embedded environment, and for this I'm using Raspberry Pi (Specifically version 2). I'm using OpenCV Library and as of now I'm using feature detection ...
6
votes
1answer
325 views

Image rescaling algorithm

Suppose I have to use bilinear interpolation to rescale image. I more or less understand how enlargement works in case of integer scale factor. But what to do with non-integer scale and especially ...
4
votes
1answer
115 views

How can I implement a complex sinusoidal function?

The following is the 2d complex sinusoidal function, $u_0$ and $v_0$ represent Fundamental Frequencies in $X$ and $Y$ directions respectively. How can I represent $j$ (imaginary number)? Edit: ...
1
vote
0answers
83 views

Image cleaning - removing all regular shapes ( circles, squares, text, icons etc. )

I'd like an automatic method to clean images. I've been looking at the GIMP, and its command line (cli) interface, in scheme / lisp. It looks very promising, but I'm a complete novice, so I'd be ...
3
votes
1answer
343 views

ping pong between same framebuffer two color attachments

In order to optimize I'm trying to set up a setup which ping pong between same framebuffer two color attachments to apply some postprocess effects. It seems to work (effects are applied) but ...
5
votes
1answer
650 views

Is it better to blur the input or output of an edge detection shader for noise reduction?

To reduce noise of edge detection the norm seems like it is to apply a blur. However, is it generally better to apply the blur to the input of the edge detection. The input in my case being the depth ...
1
vote
0answers
49 views

How do you sample an analogue image and store it in a true-colour frame buffer? [closed]

I really cannot get my head around on this issue - how does an analogue image is sampled and then stored in a ture-colour frame buffer (e.g. in a camera) and how do you prevent noise when you do so? ...
1
vote
0answers
49 views

Removing a darkened caption with text on it in an image

Alright so I'm a complete n00b at image processing so forgive me if my question sounds vague. I'll try to supplement it with what I have learnt until now and also a couple of images. See the caption ...
5
votes
1answer
72 views

DLT algorithm (4+ points) not working, what's missing?

I'm doing a direct implementation of DLT algorithm but I can't figure out why, at the end the matrix H I get doesn't (even remotely) produce x2 = H*x1 The algorithm is not that complicated so I can't ...
8
votes
2answers
2k views

What is bilateral upsampling?

I've worked with various interpolation algorithms including linear, cubic (and bilinear and bicubic), other bezier (and nurbs, etc) based interpolations, lagrange interpolation and some others, but I ...
2
votes
0answers
94 views

SIFT Feature Extraction

I am trying to implement the SIFT feature extraction algorithm. I have a few questions which are not very clear from the paper: When interpolating the extrema with 2nd order functions, do we upscale ...
5
votes
1answer
988 views

Image rotation algorithm

I would like to rotate a raster image by an arbitrary angle. I don't really care for speed: the rotation should be of highest quality possible. Could someone please suggest a suitable algorithm? I'm ...
4
votes
1answer
105 views

How to detect a screen in a photo

Is there a way to make a difference between a photo of an actual object and a photo of an object through a computer or smartphone screen. For example: how can I detect that the second image is taken ...
2
votes
1answer
197 views

Unwinding an image on a spiral to make it long and flat

Here's an odd intellectual puzzle. Something I was daydreaming about on a train - but the maths are somewhat beyond me. How would someone go about un-winding a spiral to produce a long flat image? ...
2
votes
0answers
73 views

Bilinear Transformation not working

I implemented this algorithm to fit given image to specified quadrilateral but the output is blank. I implemented it in C# as follows ...
6
votes
1answer
171 views

Converting raster shape/blob into displacement map

I am a beginner in digital image processing and computer graphics. I would like to program a similar behavior than the Shadermap 3 normal editor (displacement layer more specifically). As shown in ...
5
votes
1answer
90 views

Seamlessly transitioning between nearby environment maps

I'm wondering what is the best way to achieve an effect like here: https://matterport.com/try/ when the camera is traveling between points in space. Apart from simple color crossfade there seems to ...
2
votes
0answers
310 views

Template matching subpixel accuracy

I use template matching to detect a specific pattern in image.The shift determined is very shaky. Currently I apply it to R,G,B channel separately and average the result to obtain float values.Please, ...
5
votes
1answer
200 views

SVG opengl implementation - strokes overlap on transparency

I am trying to implement svg rendering by opengl using meshes. In paths with opacity less than 1, the color of overlapping strokes add up. But it should be like this the opengl calls are: ...
6
votes
2answers
2k views

Rotate image around its center

I'm struggling with a problem with image rotation. I'm using the idea of "Rotation by area mapping" in the following link: http://www.leptonica.com/rotation.html My c# codes are as follows. The idea ...
4
votes
2answers
837 views

How enlarge parts of a video like snapchat lens filter

I writing the this video process app which requires the each video frame to be processed such that parts of the video are enlarged. As a reference, one of the snapchat lens filter enlarges the eyes of ...
6
votes
1answer
156 views

What is the state-of-the-art on using computers to “clean-up” images?

TWO PART QUESTION - We've all seen the movies/TV shows where the police/feds/spies use computer software to take a grainy photo and do a "clean-up" to see a better picture and more details. I assume ...
5
votes
1answer
489 views

Instagram's fade effect

What is the pixel-level explanation of the fade effect, that was first popularized by Instagram? I want to implement this effect programmatically—that is, I want to understand what this effect is ...