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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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/...
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Why do red, green, and blue make up all the colors?
Why do red, green, and blue combinations can make up all the visible colors?
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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 ...
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For shader math, why should linear RGB keep the gamut of sRGB?
sRGB is often contrasted with "linear RGB."
Images are stored on disk and passed to displays in sRGB, which is approximately perceptually uniform in intensity.
Shader math is done in linear RGB, ...
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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 ...
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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 "...
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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 ...
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What is the most physically accurate representation of color possible in computer graphics?
I am looking for theoretical and implemented models to represent color in software that strives for physical accuracy.
I know that "color only exists in the mind" and that it sort of does not make ...
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Understanding Jump Flooding Algorithm (JFA) for Voronoi Diagrams
I'm having trouble understanding the JFA. As far as I understood the algorithm, it walks log(n) times through every pixel (no matter if it is a seed or not) and looks at that pixel's neighbors in $(x+...
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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 ...
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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 ...
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Why does checkerboard pattern on a computer screen appear with a yellowish tint?
This question was originally asked on Physics, then moved to Cognitive Sciences.
Consider the following image:
You might want to display the image in a new page, in case it gets resized for mobile ...
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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 ...
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Encode two R11G11B10F buffers into one using Y'CbCr?
We are trying to optimize Lighting in fillrate. Integrated graphics chips are very slow in memory access.
There are two Light Buffers: one for Diffuse and one for Specular. Both use format R11G11B10F....
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How much precision (half, float, double, etc) is enough for a Color class?
While doing some reading on how real-time applications handle color under OpneGL, I noticed that some examples implemented Color as a collection of 4 floats, while ...
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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 ...
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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 ...
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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 ...
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How to correctly render visible spectrum with uniform intensity?
I'm trying to get the correct representation of visible spectrum to render on the screen. My current progress is with using CIE 1931 standard observer color matching functions analytically ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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What determines the color gamut of a display?
I’m not sure if I’m posting this question in the right area but, I’m wondering what determines the color gamut of a display?
Is or hardware down to the RGB filter built into a display like a monitor ...
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How do I calculate average hue, since the numbers loop around?
If I calculate the average (mean) hue of a set of colours naively, I will get silly answers sometimes.
For example, in HSB/HSL, the average of hue=10 (slightly orange red) and hue=350 (slightly blue ...
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Color transform algorithm (that also works on saturation and value/lightness)?
To change particular colors in an image, generally you multiply the RGB by a transformation matrix. Image manipulation programs such as gimp & photoshop have a selective color change function that ...
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Calculate an equally bright grey to a linear RGB colour
I'm trying to get a grey linear-RGB-triple that is equally bright as another (colorful) RGB-triple.
I have to admit, that there is great confusion for me with all the color stuff, even though I read a ...
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Is there a way to interpolate color across the line with only integer calculation ?`
Here is my function that does interpolation
...
user3437
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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 ...
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Confusion between usages of linear RGB and sRGB
Suppose you have generated an image using linear values for RGB channels. E.g. you linearly interpolated it when doing blending, etc.. When you're going to present this on the screen, should the ...
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"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 ...
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How do you deal with clipping when rendering to a limited colorspace?
In my naïve raytracer experiment I work internally with RGB values, and after all the tracing has been done, I end up with raw RGB triplets that I need to write down to some image format with a ...
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Generating and Combining Spectral Colors
I have two somewhat related questions to ask:
What is the most accurate way to get the colors of a spectrum, without having to go deep into physics and simulating the universe? ;) Right now, I'm ...
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Getting contrast color to a given color in RGB or ARGB or HEX
I am looking for a stable way to find a contrast/inverted/opposite color to a given one.
Application of this is to find best possible color for foreground to give background.
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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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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 ...
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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 ...
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How can you interpolate over an array of say 5 colors?
I have an array of color values. I have an interpolating parameter, t, which varies from 0 to ...
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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 ...
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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, ...
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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 ...
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What is the purpose of this cube in color quantization?
So, I go to install GMIC for Gimp via the package manager and landed myself upon the demo program. I have discovered things such as Hough transform and color quantization. So, I get the number of ...
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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 ...
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Color of the Sky [closed]
What is the color of the sky depending on the time?
I'm looking for a set of colors (HTML-Code), the sky has during sunrise, morning, forenoon, noon, afternoon, evening and sunset. A formula to ...
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How to properly color particles in N body sim?
In my n-body simulation I would like to color the particles in way which corresponds to the magnitude of the net force acting on them.
This is so that I can confirm visually that the particles ...
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Why would a 4d texture be used for color conversion?
You can perform color conversion as a post process step to convert a rendered frame's colors to a different set of colors.
You might make darker colors more blue for instance, to give it a night time ...
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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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RGB nonlinear, what does it mean?
What does it mean and why is it not well suited for describing colors by human?
Is CMYK nonlinear also?
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What are the advantages of having two chroma channels and a luma channel vs. three chroma channels?
RGB has the advantage over schemes like YPBPR in that it's more intuitive to understand, so why use the latter? The only advantage I can think of right now is that it allows you to encode greyscale ...
