Color notes - references, links, and unsorted stuff
| 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
Digital sound and processing
- 1 Unsorted
- 2 References and other links
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?).
- 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
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
- StW, I1I2I3
- Retinal Cone
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)
Web gamma: http://hsivonen.iki.fi/png-gamma/
Color pickers / color schemes / color coordination, often for styles
- http://www.degraeve.com/color-palette/ bases colors on image
- http://pourpre.com/colordb/?i=c486A95&l=eng - harmonies and such
- http://www.telecable.es/personales/alberto9/color/index.htm - funky flash app
- http://fugal.net/vim/rgbtxt.html - color name list
(considering color blindness and such):
More links: http://www.tlbox.com/web_designers/color