# Questions tagged [color]

Questions about the visual perceptual property deriving from the spectrum of light, usually expressed numerically according to a color model.

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469 views

### How to determine RGB values given a display spectral response curve?

I am reading Physically Based Rendering section 2.2.2 on RGB color. I am trying to understand how, given a display spectral response curves for rgb intensities, we can choose the intensities so that ...
47 views

### value range in CIEXYZ space

When converting from sRGB to CIEXYZ I seem to be off by a factor of 100 I'm trying to convert from sRGB to CIELAB. Calculation First I need to go from sRGB to CIEXYZ. Using this formula I get i.e. ...
24 views

### Normal blend mode math

I have one question. How to calculate source color after blending operation. For example. I have 1 - Background color (r-115, g-94, b-67, a-1) 2 - Foreground color above background color, which ...
209 views

### Determining input color space primaries from spectrum data

If I have an output device, for which I have a known spectrum data for each of it's primaries, I should be able to calculate the CIEXYZ of its primaries using using the integral equations together ...
49 views

### Does CMYK values provide more colors than RGB?

We know that in the RGB system we have three primary colors and each of them has a value from $0$ to $255$ (or $256$ values in total). So all possible colors are $256^{3}=16777216$. But in the CMYK ...
65 views

### Converting ACES ap0 color space into srgb?

I'd like to know the correct when of converting ACES AP0 color space into sRGB. Let's say artists decide to pick colors outside of sRGB in AP0, will ACES handle this situation correctly, meaning no ...
93 views

### With a light source at (0,2,0) and unit cube (from [-1,1]) using a given shading formula, how is the r,g,b for each surface calculated?

The above problem is from a past Computer Graphics exam. I am particularly confused about the explanation given, firstly for the top and bottom planes (since the direction of normal for top plane ...
1 vote
236 views

### Applying Phong illumination to a colored surface

The formula for Phong illumination as given on Wikipedia (see there for the variable definitions) is: I_\text{p} = k_\text{a} i_\text{a} + \sum_{m\;\in\;\text{lights}} (k_\text{d} (\hat{L}_m \cdot \...
25 views

### Is there a way to automatically optimize imags based on predefined marker on image?

Color correction is tricky. It's always a lot of work to make everything look same. I have multiple products (clothing) to take a picture of. One is 100% red, other 100% Orange. Some are multicolor ...
13 views

### What is the color space of Luminosity blend mode and other three blend modes that photoshop use , HSB HSL or LCH

Here is what I have tried: I create a base layer and a blend layer and I choose Luminosity blend mode, so the result suppose to have the hue and Saturation of the blend layer and the Luminosity of the ...
25 views

### What happens when we select lower resolutions on a high-resolution monitor?

I have a monitor with a resolution of 1360x768 (16:9), When I set the resolution to 1280x768 (5:3), 1024x768 (4:3), 800x600 (4:3), even 1920x1080 (16:9) it completely covers the screen and the monitor ...
176 views

### Algorithm to reduce number of colors used on an image. (sRGB)

Introduction: I have a program that receives an image as input and does stuff. The more colors the image has the longer it takes for the program to finish and the less visible the difference between ...
216 views

### Painter's algorithm test 2 and test 3?

TEST #2: Surface S is completely behind the overlapping surface relative to the viewing position. S1 is completely behind/inside the overlapping surface S2 How to check these conditions? i) Set the ...
223 views

### How to find the nearest palette color when dithering in RGB

I maintain an image dithering library and command line tool. When I was initially developing the library, I was trying to figure out how to match dithered RGB values (containing quantization error or ...
152 views

### Why are the HSL and HSV color models not considered "perceptually uniform"?

The HSL/HSV color spaces are not considered "perceptually uniform" despsite being widely used. Is there a detailed reason for this?
36 views

### How to add HemisphereLight to a simple threejs scene?

I'm trying to add light and see its changes in a simple scene in threejs but no matter the intensity or the color I set for the light, I see no change in a scene. Actually, if I don't include the ...
415 views

### Why does my Dell laptop monitor give this weird color banding?

I've noticed some very obvious color banding on the screen of my Dell Precision 7750 laptop while watching video (same in every video program; VLC, built-in Windows video player, etc.) Not only does ...
1 vote
152 views

### What are the main concepts behind building the plasma effect with GSLS?

By the plasma effect I mean an animation that looks like this: I have seen some codes, like these https://www.shadertoy.com/view/Xst3zN https://www.shadertoy.com/view/4tdGWX and messed with the code ...
145 views

### Interpolating HSV color with black

I'm interpolating RGB values by transforming them into HSV space and then back into RGB. I have trouble figuring out how to achieve ...
69 views

### How to visualize color synthesis in HSL diagram

before considering the HSL color space, let's consider the CIE chromaticity diagram to understand what I'm looking for: Unless I am mistaken, I read it that way: Given two points A, B, any color in ...
1 vote
78 views

### Using the Preetham/Shirley/Smits daylight model to get practical (s)RGB values

I have implemented Preetham, Shirley, and Smits’s daylight model using Aubrey Jaffer’s Scheme implementation as a reference and confirmed that my implementation produces the same results in the xyY ...
159 views

### Confusion about HDR image pipeline

I am working on a path tracing renderer, and I want to produce an sRGB image out of the HDR image buffer I get at the end of my rendering algorithm. Up until now I have worked just by clamping values, ...
3k views

### ACES tonemapping confusion

In different sources I see ACES tonemapping, but I see one of two possible sets of formulas: https://www.shadertoy.com/view/XsGfWV this one https://www.shadertoy.com/view/tdffDl or this I compared ...
2k views

### How do I add two color values containing alpha?

I started out writing my Color class as just containing R, G, B triplets. Adding colors in this situation turns out to be fairly simple. ...
181 views

### Why do some texture data formats only have the red channel?

While programming something in Rust with the BevyEngine, I came across TextureFormats. My understanding is that those are used to define how the pixel data is handled. So Rgba8Unorm means that there ...
302 views

### Why do computers more efficiently store black colors than white colors in computer graphics?

I have a question about how colors are stored in computer graphics. I had watched this video previously which had explained about why colors are stored and displayed differently than one would assume ...
1 vote
388 views

### How to change a RGB value using a radiance value?

I am new to this awesome community, I am currently writing a ray tracer but I hit a problem... Let's say I have a surface(material doesn't matter) of colour [1, 0, 0] in RGB, and the radiance reaching ...
3k views

### What is a good color similarity metric?

I have some colors in RGB in [0,1] and want to find a way to rate their similarity, as perceived by a human. I have two ideas in mind, but I am sure there are other options as well, but am unsure ...
1 vote
79 views

### Is spectral response curve and spectral power distribution the same thing?

I'm reading section 5.2 of pbrt 3rd edition and came across the part where they explain the concept of RGB colors. When we display an RGB color on a display, the spectrum that is actually displayed ...
99 views

### Why do materials have both an ambient color and a diffuse color?

One of the first things I learned about computer graphics lighting (and light in general) is that when a ray of light hits a surface, the surface absorbs certain colors and the light retains the rest. ...
234 views

### Question about function for color

I would like a help to understand the following line of code: return float3(pow(color.r, 2.2), pow(color.g, 2.2), pow(color.b, 2.2)); I've seen some places calling ...
51 views

### Animated rainbow distortion wave effect

https://foundation.app/mg/20210227-3lau-makes-history-1790 The link above shows a video animation that has a rainbow wave distortion effect applied to it, that ripples across the video. how, and in ...
62 views

### What is the name of this moving color pixels effect, for animating a painting?

https://superrare.co/artwork-v2/spring-22267 The artwork in the link seems to be based on a painting of a woman, but effects have been added that assign a pixel to each block of the painting that ...
1 vote
64 views

### Name and influence of style used for futuristic line patterns?

What is the name of the style of the line graphics used in the image below? The line patterns seem to envelope the shape of the woman maybe algorithmically somehow, becoming denser and yellow on the ...
226 views

### "whiteness" in center of bright colored lights - what is it called?

When a source of colored light is very bright, it's center appears white. What is the term I need to look for so I can implement this in my shader? I have added an image which is an example of what I ...
1 vote
55 views

### Colour Depth in Hardware

I hope this is the correct place to ask this question. It feels to me that I should ask people who have had to program graphics as there’s a lot of confusion about color depth in general. I’m sure a ...
1 vote
301 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, ...
1 vote
150 views

### Raytracer help - Background color writing over some colors?

I'm implementing Peter Shirley's "Raytracer in a Weekend: The next week" and I'm having some trouble with rendering a scene with a light. I'm not sure if the issue is the background color or ...
1 vote
56 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 vote
177 views

### Weird glColor3f results in framebuffer objects

The code is glColor3f(1, 1, 1); gluSphere(gluq, 0.2, 10, 10); glColor3f(1, 0, 0); glTranslatef(1, 0, 0); gluSphere(gluq, 0.2, 10, 10); In short, when I draw ...
3k views

### Why is there a difference between the CIE XYZ colour gamut vs CIE RGB?

Yet another question about colour space... In my research on CIE XYZ system, I found that it is based on the CIE RGB colour matching experiments, and that because the RGB system needed occasional ...
100 views

### What is the relation between colour spaces and what is actually displayed on our screens?

I am not entirely sure that this is the right stack exchange, but I couldn't find any other suitable one - please redirect me if necessary. There exists mathematically defined colour spaces which help ...
1 vote
322 views

### How could I remove this colour interpolation artefact across a quad?

I've been reading up on a vulkan tutorial online, here: https://vulkan-tutorial.com. This question should apply to any 3D rendering API however. In this lesson https://vulkan-tutorial.com/...
53 views

### Aligning (matching) colors (white balance, brightness) of two scenes based on reference object

What I am trying to do is to become able to compare with reasonable accuracy two real world fabric/textures (colorwise speaking) at two distinct locations. I can't move them into single place to ...
1 vote
46 views

### How to get "Equal" (saturation, brightness) Red and Green Colours in a Web-based Application?

I am looking for a red and a green hue that are equally discernable against a gray background on any PC monitor, using HTML/CSS-based application. There are many possible solutions to balance these ...
1 vote
21 views

### Alpha part of color class or shape class

I am designing a 2D drawing library (it is its very early stages) and I was wondering what to do with Alpha (transparency). I have two trains of thought: A. Implement Alpha in the Color class ...
101 views

### What is the CMYK color profile used by pantone.com

Pantone spot colors are specified in the RGB and CMYK color models on the https://pantone.com website. For example, the Pantone 122 spot color as it appears when printed on coated paper is specified ...
1 vote
3k views

### How can I draw this style of grid?

I'm trying to write code (in any language) to render this 3D grid, matching the look and colors as closely as possible: