Color notes - references, links, and unsorted stuff

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These are primarily notes
It won't be complete in any sense.
It exists to contain fragments of useful information.
This page is in a collection about both human and automatic dealings with audio, video, and images, including


Audio physics and physiology

Digital sound and processing


Image

Video

Stray signals and noise


For more, see Category:Audio, video, images

Unsorted

http://en.wikipedia.org/wiki/Deep_Color

http://en.wikipedia.org/wiki/XvYCC

Grayscale conversion from RGB

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

The easiest conversion to grayscale is a simple average, (r+g+b)/3, but this is not very perception-accurate.


There are various RGB standards that mention grayscale conversion as weighing of the channels. In some cases this is based on perception, in some it correction for RGB primaries used in the standard (probably based on phosphors?).

These include:

  • ITU-601-1 and a few others use nearly identical numbers, 0.298954*R + 0.586434*G + 0.114612*B (apparently originating from CIE-XYZ 1931(verify))
  • EBU/ITU 3213 (PAL(verify))): 0.222*R + 0.707*G + 0.071*B
  • BT/ITU-709 (NTSC(verify))): 0.213*R + 0.715*G + 0.072*B
  • ...more


The best choice depends mostly on what sort of RGB you have.

It can also depend on specicic wishes. Consider how photographers sometimes use specific colored lenses (or nearly-equivalent photoshop filters) for specific effects, such as lessening the visibility of freckles, making skies more contrasted, and such.


Undetailed so far

Mostly colour spaces, colour models, and transforms. Again, these are not necessarily accurate.

  • HSV, HSB, HSL/HLS, HSI - hue, saturation, and brightness/level/luminisity/intensity. * IHS,
  • NTSC YIQ, NTSC CMY
  • YUV, YIQ, YCbCr
  • CMY, CMYK
  • HMMD
  • StW, I1I2I3
  • Retinal Cone
  • Munsell
  • Karhonen-Loeve

And things I've read about them:

  • NTSC RGB seems to refer to the defined conversion from YIQ to RGB inside the TV.
  • SMPTE RGB apparently does the same but matches modern phosphors better.
  • IHS conversions seems inconsistently defined between books.
  • I1I2I3 is defined from an (unspecified?) RGB as I1=(R+G+B)/3, I2=(R-B)/2, I3=(2G-R-B)/4, so seems to be a luminance-and-opposite type of system.
  • CIE L*a*b* apparently agrees with Munsell's colour system well.


File format notes:

  • GIF stores RGB
  • JPG stores RGB, YCbCr, or CMYK (verify)
  • PNG is RGB (sRGB unless it stores an ICC profile)


http://color-management-swicki.eurekster.com/device+independent+color+space/


Web gamma: http://hsivonen.iki.fi/png-gamma/

http://www.libpng.org/pub/png/png-gammatest.html

http://www.libpng.org/pub/png/png-colortest.html

References and other links

Technical

General


CIE stuff


Illuminants


Psycho-ish


Formulae


Other



Websites

Online calculators

Color pickers

Color pickers / color schemes / color coordination, often for styles





Social scheming


Reference lists


Usability

(considering color blindness and such):

Other/unsorted




More links: http://www.tlbox.com/web_designers/color

Software