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Questions tagged [image-processing]

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16 views

Open source tools for extracting hi-res images from video

I found recently an article in which they describe a technique to extract high resolution images from a standard quality videos. The technique exploits the fact that in a typical video the camera ...
1
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1answer
37 views

How to translate the center of an equirectangular projection?

I'm trying to perfectly align two or more equirectangular photos of the same place taken from slightly different positions. Using an example provided by openMVG I managed to get the relative position ...
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0answers
42 views

Lanczos filter implementation issue

I tried to follow Nathan Reed post Antialiasing: To Splat Or Not to implement splat method. The image I am getting thorugh the Lanczos filter is very different than Nathan. I do not understand where ...
3
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1answer
74 views

Tiled Image Palettization Algorithm?

In most cases today, image palettization consists of reducing the overall number of colors in an image to some fixed number globally. This is typically solved as a straightforward but computationally ...
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0answers
58 views

Why don't discretization errors occur with compute-shaded kernel filters?

An efficient compute-shaded image filter would be emitted with (screenX / [kernel width], screenY / [kernel height], 1) groups and one kernel in each group, allowing texels to pass into groupshared ...
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1answer
29 views

Can you generate your own HDRI maps without using photos?

For example, preparing a scene in Maya using standard lights and rendering out a panorama? Could they also be made from scratch in photoshop using 32bit color? Is there a reason why people don’t ...
3
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1answer
74 views

Adding noise to gradient

I found this picture When you zoom in to any part of the image, the background looks a bit noisy/grainy. See pixels around "violent violet" label: I'm trying to understand how to achieve the same ...
1
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1answer
115 views

Convert RGB image to YUV420 using a hlsl shader

I am new to shaders and I need to convert efficiently an RGB image to YUV420. I can convert the RGB image to YUV420 with a simple c++ program that uses the ...
4
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1answer
63 views

How to shift color values of a single RGB channel

I’m a weaver and textile maker with no prior coding or programming experience. In researching and reading through posts on this and other message boards, I was able to find a lot of useful information,...
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1answer
46 views

Resolution issue of generating a PNG icon for macOS menu bar

Wonder if anyone has experienced this. When generating png image icons for macos. its recommended at 19x19 pixels. However, based on that, the icon (shield) that is generated is pixellated compared ...
1
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1answer
37 views

How to blend a segment of an image with another image

I want to put a segment of an image to another image. But to make it realistic I applied poisson blending. But the output is not good at all. Output without poisson blending. The kid was cropped ...
2
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2answers
127 views

Calculate the average color of an image

I want to calculate the average color+opacity of an image. First I thought about just averaging all ARGB values component-wise, but this got really dark on images with a lot of transparency. I also ...
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0answers
45 views

How to ensure that the raytrcing coordinate system is teh same as the projection one?

I have 2 shading models right now, one is using voxels the other one is the standard projection absed renderization method. Putting them side by side I have noticed that no matter what I do one is ...
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1answer
66 views

Difference between Cropping, Scaling, Resizing & Changing Aspect Ration of an Image?

I've got a new task related to image processing in a website. I am too confused in understanding different terms used with sizing of an image. What is the difference between: Cropping an image ...
1
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1answer
68 views

Quick 2-color quantization for small images

So I have a small (8x8 pixel) image in 24-bit color. I want to be able to (quickly) generate a color-quantized version of the image that only has two colors. One naive approach is to cluster a luma ...
2
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2answers
93 views

What blend mode is this?

I asked this on Graphic Design but was unable to get any relevant help from them. I'm trying to reverse engineer a blending mode I've seen on a picture: This image was created by someone else ...
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0answers
46 views

Tanget plane of an image

My problem is about tangent plane. I have an image (m by n). I obtain surface normal vector using machine learning methods. Then i would like to obtain tangent plane for this surface normal. To ...
2
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2answers
185 views

How to generate the stereographic projection of a 3D model

Given a 3D model, is there a way to stereographically project it to a 2D image? In particular, I would only need a little more than half the model (the lower half) to be mapped to the plane (mapping ...
4
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1answer
240 views

Creating depth map from a 2-D image?

My question is oriented towards the generation of depth map using any of the state of the art depth sensor. However, each of these method required the presence of an 3-D object in front of the sensor....
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0answers
67 views

Image Processing: Photogrammetry [closed]

I am new to image processing but I am currently exploring myself in 3D reconstruction during my leisure time. I have decided to use openCV (eg. edge detection, possible?) in C++., maybe with a little ...
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0answers
77 views

Ray Tracer Shadowing

So I'm working on an assignment where we have to design a simple ray tracer. The program has two objects that it can use, sphere and cube. It can render the cube and spheres, it also does shading on ...
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1answer
116 views

why not use hash function image instead of jpeg?

Why don't we just use an hash function to reduce the size of an bitmap,rgb raw image?isn't it more efficient of storage data and it produces lossless image after being decoded?The decoder is also very ...
2
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2answers
700 views

Passing parameters in Metal Compute Kernel using Swift 4

On the CPU side, I have a structure I want to pass to the compute kernel: ...
0
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1answer
50 views

How does image resolution change(process involved in calculation), when a screen on phone is rotated?

What is the process involved in calculating the resolution of image to be displayed when the screen of my phone(android) is rotated? My screen resolution is 1920x1080. It displays some videos only in ...
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2answers
109 views

Can I get numeric data from a color map?

In my class I often need to work with color map images. I would show the image and try to make inferences/observations about different subjects. Often times I need to actually quantify some aspects, ...
2
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1answer
178 views

Histogram of image intensities

I want to create a histogram of intensities 0.1, 0.2, .... 0.9, 1, from an image rendered using OpenGL and C++. How can I do this? Can I access the pixel intensities in the framebuffer somehow? Also, ...
3
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0answers
36 views

Sub-pixel image registration using phase

Currently I'm trying to reproduce the result by the academic papers Sub-pixel Shift Estimation of Image based on the Least Squares Approximation in Phase Region by Fujimoto, Fujisawa and Ikehara (...
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0answers
63 views

How to make Convolved Diffuse and Specular image in C#

I am trying to take either a HDR panoramic or HDR cubeMap and from that create a Lambert Irradiance environment map and a Cook-Torrence Specular environment map. I am stuck at the proper ...
4
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0answers
145 views

Sinc interpolation and Ideal reconstruction example

I am trying to apply sinc interpolation on this data set. The patches in the left image is a snapshot of AutoCAD 3d faces. Lux values are calculated for centre of each patch that are in 0.3m x 0.3m ...
9
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3answers
965 views

What's a proper way to clamp dither noise?

When reducing color depth and dithering with a 2 bit noise (with n=]0.5,1.5[ and output=floor(input*(2^bits-1) + n)), the ends of the value range (inputs 0.0 and 1.0) are noisy. It would be desirable ...
1
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1answer
57 views

How to plot an input signal in image?

Given an input signal(ex. sine) how can one go about plotting an image like below ones(the stripped black and white image)? The images are from these slides on image processing. Or this one:
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1answer
59 views

Matlab scatter hotmap [closed]

I have two columns of data, x(angle) and y(distance), they are my experiment results(figure 1). How can I use these results to make a ‘hotmap diagram’ by matlab? The z axis is the density value of xy ...
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0answers
37 views

3D reconstruction using 2D matched points

I have 2 images, called left and right images. I have some matched points $[c_l,r_l]$ and $[c_r,r_r]$ in both of them (these points are in pixel coordinates). For a 3D point in the real world, they ...
4
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1answer
134 views

Why does an affine transform work only on three of the corners?

I am trying to use a linear transformation to straighten out the camera angle on this image: In other words, I want to transform the image into a head-on view of the whiteboard. I applied an affine ...
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2answers
90 views

How do I do batch conversion (preferably in MATLAB) from .gif images to .off or .stl mesh files? [closed]

I'd like to do a batch converison of 1400 .gif images into .off or .stl format files that'll be meshed images. Two sample .gif images are attached. How can I do this conversion possibly by a free ...
1
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1answer
63 views

Extracting the green-screen region borders

Given a png image with an unknown number of green colored (rgba=0, 65535, 0, 65535) regions 1- How can I find and put the border points of only the separate green boxes to an array like: ...
3
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1answer
261 views

Why is the line from the camera to vanishing point parallel to the other parallel lines?

When trying to find the vanishing point of an image, why is it that the vector from the center of the camera to the vanishing point is parallel to the parallel lines of the image? What's the ...
3
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1answer
86 views

How would I convert a picture of a slanted surface into a straight one? [duplicate]

Suppose I took a picture of a whiteboard at an angle. If I could detect where the corners of the whiteboard are, what algorithms and linear projections could I use to convert this slanted view into a "...
2
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1answer
399 views

How can I combine two filter kernels for image processing to create a single kernel?

Is it possible to create a single kernel which can help us to perform an 2 step image processing? For example, I want to first perform a median filter on my image to remove salt and pepper noise and ...
4
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2answers
361 views

Making low discrepancy sequence noise textures, not LDS sample positions

When making sampling locations, there is a lot of information out there on how to do white noise sampling, uniform sampling, uniform+jittered sampling, low discrepancy sequence sampling (eg halton) ...
4
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1answer
193 views

Was Evans & Sutherland CT5 really created in 1981?

A few days ago I found a video on Twitter showing the Evans & Sutherland CT5 Flight Simulator system. It was labeled as 1981 footage and looked really amazing. The first time I saw similar 3D ...
1
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1answer
368 views

Bilinear Interpolation

I am trying to implement bilinear interpolation as described in the paper Spatial Tranformer Networks by Jaderberg et. al (see link to paper). They describe bilinear interpolation in Equation 5 as: $$...
2
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0answers
137 views

Making an approximately constant color or brightness image

I've been working on implementing the technique from the paper "Designing look-and-feel using generalized crosshatching" which can be found at: http://dl.acm.org/citation.cfm?id=3085054 The paper ...
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0answers
279 views

Getting improper undistorted images for stereo calibration

I am trying to calibrate stereocamera using left and right chessboard images available at github.com->opencv/opencv/tree/master/samples/data After undistorting them, left images seem to look right ...
2
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1answer
136 views

What is a common approach to smooth structures in textures?

I have a screen-aligned texture resulting from multiple rendering passes. It looks about this: I want the edges to appear smoother than they do now (but still keep their characteristic shape). When ...
1
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1answer
68 views

Appropriate filter steps for resolving a droplet pixel

I have a series of images obtained from a microscope as follows I need to create a series of filters that would isolate the centre section on the yellow droplet.(This is highlighted by the bright ...
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0answers
80 views

How to merge multiple exr into a single multilayer exr?

Are there some tools or softwares to merge multiple exr into a single multilayer exr? I only find a tool to split a multilayer exr into multiple exr. And it seems that Blender, Mitsuba, Darktable ...
4
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1answer
45 views

can half of a picture be processed and viewed?

Lets say i have a picture. I send it to a server. While sending it to the server half way the upload gets canceled. Now the server has half or some of the picture. Now is there a way in which this ...
6
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1answer
709 views

Tone Mapping & Gamma Correction

I've been looking up this question on the internet for a while, and I haven't been very successful, so I decided I'll ask it here. Should I apply tone mapping before gamma correction, gamma correction ...
4
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0answers
66 views

Slope Based Texturing

On the main page for Allegorithmic's Bitmap2Material, it mentions that the software uses a Slope Based approach over a Luminance Based approach. What exactly does this mean?