# Questions tagged [color]

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75 questions
40 views

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 ...
913 views

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

Here is my function that does interpolation ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 "...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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/...
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 ...
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 ...
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 ...
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 ...
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 ...