# Tag Info

Accepted

### Why do red, green, and blue make up all the colors?

Let's reminds ourselves what light is. Radio waves, micro waves, X rays and gamma rays are all electromagnetic radiation and they only differ by their frequency. It just so happens that the human eye ...
• 4,420

### Why do red, green, and blue make up all the colors?

They don't. The problem with the diagrams representing the visible and RGB gamuts is that they're presented on RGB displays. They obviously cannot show you what they cannot show you : the area inside ...
• 301

### Why do red, green, and blue make up all the colors?

Humans are trichromatic, which means we have 3 different kinds of color receptors (better known as cone cells), each sensitive to a different set of wavelengths: Image source: wikipedia So it only ...
• 5,970
Accepted

### "Light intensity" of an RGB value

The short answer: no, but if you are interested in details, please keep reading (: About lighting units Light “brightness” is indeed quite poor/ambiguous layman’s definition for brightness of a ...
• 3,666
Accepted

### How much precision (half, float, double, etc) is enough for a Color class?

Colors shown on your display or saved to standard image file formats use 8 bits per component. So to store these colors it suffices to use four bytes (unsigned char)...
• 25.1k
Accepted

### Applying correct light physics to gaussian blur formulas for glow

Yes, your theory is correct. A gamma-correct blur entails converting the input pixels to linear color space, performing the blur weighting and accumulation in that space, and then converting back to ...
• 25.1k
Accepted

### What is the most physically accurate representation of color possible in computer graphics?

The most physically accurate way would be to have a $l(\theta)$ which for each possible color frequency has a certain value. Converting to RGB would then need a frequency responce function for each ...
• 5,970

### What is the most physically accurate representation of color possible in computer graphics?

There is spectral rendering, where you can quantize the visible wavelengths from ~390nm to ~700nm to N discrete wavelengths instead of the standard 3 for RGB. Then if you had to model say a prism, you ...
• 3,666
Accepted

### Generating and Combining Spectral Colors

Your way of calculating XYZ functions is probably the most efficient way to go about calculating accurate colors from a spectrum. It is standard practice afaik, for examples the books Physically Based ...
• 1,566
Accepted

### Calculate an equally bright grey to a linear RGB colour

The easiest way to get the perceived brightness of a color is to calculate the Luma. Finding the grey color with the same luma is easy - just set all of the RGB components to the desired luma value. ...
• 434

### What wavelengths(dominant) the primary RGB colors are supposed to be in sRGB color space in nanometers?

The primaries of sRGB are not pure wavelengths, they are color mixtures. Their true definition is in terms of CIE chromaticity coordinates. That said, for sRGB, the red primary is close-ish to 610nm, ...
• 25.1k

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

You are focusing far too much on the number of color codes in common implementations. There is no reason that RGB must have 256 values per component, and no reason that CMYK must have 101 values per ...
• 1,245

### Why are RGB tertiary colors so similar to RGB primary colors?

Likely a gamma correction issue. Tertiary colours are some permutation of (1, 0.5, 0) in RGB, right? So the issue arises because without applying gamma, 0.5 appears less than half as bright as 1, so ...
• 2,402
Accepted

### What determines the color gamut of a display?

The physical imaging elements of your monitor define your gamut. So things like how bright the elements can be as well as the color spectra of the color elements define the gamut. But, thats quite the ...
• 8,447

### Why do red, green, and blue make up all the colors?

They don't. Aside from what others have said about the physical reasons not, from a practical computer graphics standpoint, representing either surface pigments or light sources with RGB color is ...

### Why do red, green, and blue make up all the colors?

One more thing: "violet" and "purple" are not the same color. Violet is a pure color around 400 nm; but purple is a combination of red and blue. To our not-quite-perfect human eyes they look the ...
• 141

### Strange stripes on the gradient

The non smooth appearance, or visual stripes you see, is called color banding. (Wikipedia) It is produced since the medium, in this case your screen, is only capable of producing a finite array of ...
Accepted

### Strange stripes on the gradient

The 'jumps' to 'a bit darker' are an optical illusion due to how human perception works. Check out Mach bands in wikipedia. Now as for why you get a step function even though you have a smooth ...
• 2,226

### Can someone explain this formula for parse RGB to HSL?

First it converts the red, green, and blue values from the 8-bit unsigned integer range to floating point values between 0 and 1. It then figures out which component is the maximum, which is the ...
• 3,431

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

The XYZ and xyY models are extremely useful for certain operations such as manipulating RGB colour spaces to another RGB encoded colour space. However, XYZ and xyY fail quite quickly in other ...
• 318
Accepted

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

Correct, the missing curvy section in the green-cyan-blue area represents where the red component would have to go negative to express those colors in CIE RGB coordinates. RGB and XYZ are, at one ...
• 25.1k
Accepted

### splitting hue & saturating and leaving value behind

Removing hue and saturation ("desaturating") leads to a grayscale image with the same luminance as the original colors, for instance: (source: my own photo) It is not possible to remove hue ...
• 25.1k

### Why are YCbCr transforms defined in terms of gamma-corrected RGB?

Report ITU-R BT.2246-8 discusses this in extensive detail, starting in section 2.3 of Annex 2. The authors discuss the advantages of a YCbCr model operating on linear color (referred to as CL, or ...
• 151

### Pixel density / color channel depth ratio for dithered gradients

There has been quite some research into this using Barten contrast sensitivity function. It is the current formula behind the Dolby Perceptual Quantizer as featured in SMPTE 2084 and HDR10. This, ...
• 318
Accepted

### How do I calculate average hue, since the numbers loop around?

How do I calculate average hue, since the numbers loop around? I will get silly answers sometimes. For example, in HSB/HSL, the average of hue=10 (slightly orange red) and hue=350 (slightly blue red) ...
• 256

### Would there be a point in creating monitors that have more than the regular RGB color channels?

Has such a thing been considered? Can it be done? Would it be useful? Has it already been done? The answer, I believe, would be YES | YES | Not really | YES. You can search for Sharp AQUOS Quattron - ...
• 1,142
1 vote

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

The real story here is actually very interesting and can be enlightening. So I offer this alternate answer to help better answer this question. Also, my answer below is a very specific to this ...
• 3,344
1 vote
Accepted

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

Several reasons. Im listing them in random order There are entire industries that do other things than display things on computer screens. If you were to print a booklet, make a package, movie ...
1 vote
Accepted

### Determine paint color from a photo

In theory yes, but practically speaking, I doubt it would be very easy. First, the color may not be representable by the color space that your camera of choice produces images in. We've recently ...
• 3,431
1 vote

### YUV to HSV to RGB issues

Think about it this way. To calculate YCbCr of (1, 0, 0), you'll end up with Y = 0.299, Cb = -0.16873, Cr = 0.5. If you take the magnitude of the chroma channels (...
• 3,431

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