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Questions tagged [color]

The tag has no usage guidance.

1
vote
1answer
40 views

Fading an object in add mode with correct color math

I have a scene rendered entirely with objects with additive blend mode. I have a value that is oscillating from 0, to 1. When it is 1 the object is supposed to be invisible, 0 should be entirely ...
5
votes
1answer
913 views

Is there a way to interpolate color across the line with only integer calculation ?`

Here is my function that does interpolation ...
2
votes
2answers
110 views

Matching an HSV color with a blended color

This is hard to explain but I am going to try, then I will explain it as pure mathematics. Look at this image. So basically this is a moving line, each frame a new segment is added and the previous ...
4
votes
2answers
226 views

What is the effect of the BRDF denominator?

I was reading a paper on BRDF. I've come across this formula : $$ f(\omega_i, \omega_o ) = \frac{FDG}{4(N.V)(N.L)}$$ The (N.L) term can be cancelled by the cosine term which appears in the rendering ...
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 ...
7
votes
5answers
308 views

Why does the 1/r² term appear with point sources?

I'm currently reading some books on radiometry. They mention that radiance is constant along a ray. It doesn't change with distance. However, I've seen some raytracer and they put the 1/r² factor when ...
1
vote
2answers
337 views

Change particular color in an image

Suppose i have a image and I want to convert the portion of image that is red to blue(or any other color). One way to do this is extract red part of image using HSV or other color values and convert ...
1
vote
1answer
587 views

Spectral path tracing - image color/brightness incorrect

I implemented a spectral path tracing using physically base BRDF models such as Oren-Nayar,Specular Reflection and Transmission, Lambertian. All calculation in the path tracer uses standard illuminant ...
4
votes
3answers
671 views

OpenGL - Colours not working properly

I am using a single VBO to store vertices in the follow format: v1X, v1Y, v1Z, v1R, v1G, v1B, v2A, v2X, ... Vertex positioning is fine, shapes show up where expected, however instead of using the ...
11
votes
1answer
519 views

What does “muted” mean in the context of color?

I want to extract colors from images like in Adobe Kuler. When I select colorful or muted corresponding colors are shown. But what is the definition for colorful or muted colors? What do the words "...
7
votes
2answers
493 views

Best technique to draw overlapping colored line segments that follow the same route

I'm not too versed in computer graphics so my question may be vague. I'm given a sequence of GPS coordinates which I draw on an iOS map, and they define bus routes. Some of the bus routes happen to ...
7
votes
1answer
761 views

Function to convert HSV angle to RYB angle

I'm trying to create a RYB color wheel with a smooth-looking gradient across the RYB spectrum. The angles of the HSV wheel are incorrect (yellow at 60deg instead of 120deg etc). If I just do a few ...
12
votes
2answers
797 views

What would be the correct way to calculate saturation in this case?

I'm trying to make a HSV representation of the xyY color space. To calculate hue from an $(x, y)$ color, I use the angle between that color and red (wavelength 745) on the xy chromacity diagram, with ...
4
votes
1answer
147 views

Javascript color extraction library

I have a small project that needs to extract the perceptually-salient colors of an image, in javascript. There are a few libraries out there (color-thief.js, vibrant.js). The trouble is, I'm finding ...
6
votes
1answer
734 views

Actual vs Perceived Brightness of RGB Colour

In this video from about 1:15, it is stated that if you have an RGB value of (0.5,0.5,0.5) it is only 22% as bright as (1,1,1) rather than the expected 50% as bright. Does this mean that RGB is ...
5
votes
1answer
133 views

Is colorized subpixel rendering possible?

Subpixel rendering is used most commonly to anti alias fonts. It works by leveraging the physical layout of the color components of a display to give geometry details to an image that are smaller than ...
7
votes
2answers
179 views

Why is the CMYK space four sided in chromaticity charts

In chromaticity charts the CMYK color space is usually four-sided. I've lately had to read quite a few charts and it suddenly dawned to me that I don't really understand why. It has just not been ...
33
votes
4answers
1k views

Are there common materials that aren't represented well by RGB?

In graphics we use RGB and other color spaces as an approximation to the full spectrum of light wavelengths. This evidently works pretty well in general, but are there any reasonably common objects/...
7
votes
1answer
71 views

Finding a color perceptually similar to an image

I'm working on a program to use randomly-selected images as a desktop background. Now, not all images are the same shape as a computer monitor. One idea I had for dealing with this is to set a ...
3
votes
1answer
82 views

How is an ICC profile embedded or built into an image?

If I were to analyze or change an ICC profile embedded in an image, how should I proceed? I'd also be glad to understand how an "end-user" is able to create these with a tristimulus colorimeter or a ...
7
votes
2answers
153 views

How can I detect edges between different colours of the same brightness?

I'm looking for an algorithm that can identify edges across which colour is changing sharply, rather than just finding changes in brightness. Is this just a matter of using a different colour space ...
6
votes
1answer
231 views

How to do a color separation with more than 3 primary colors

How would one do a color separation if there are more than 3 color primaries, or the primaries are nonstandard. In Standard CMYK conversion K is relatively easy conceptually to figure out. Its just a ...
7
votes
1answer
159 views

Brightness and contrast VS Gamma, is it possible to identify the gamma “correction amount”?

Trichoplax question aroused my curiosity and the answers in this question also reminded me why I sometimes use different gamma "amounts" to enhance images. Therefore, is it possible to determine the ...
16
votes
2answers
431 views

Is gamma still important to take into account?

Do different monitors (including mobile screens) still use significantly different gamma functions when displaying colour images? Is there a standardised way to represent colour that can then be ...
9
votes
1answer
79 views

What are the side effects of biasing brightness in continuous spectrum raytracing?

I want to model rays with a continuous range of frequencies so that I can get raytraced images with colour separation on refraction. I can model a light source with a specified frequency distribution ...