| Extracted from Pike v7.8 release 700 at 2013-06-08.

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Image.Colortable

# Method Image.Colortable()->cubicles()

Method cubicles

  `object cubicles()`
  `object cubicles(int r, int g, int b)`
  `object cubicles(int r, int g, int b, int accuracy)`

Description

  Set the colortable to use the cubicles algorithm to lookup the closest color. This is a mostly very fast and very accurate way to find the correct color, and the default algorithm.

  The colorspace is divided in small cubes, each cube containing the colors in that cube. Each cube then gets a list of the colors in the cube, and the closest from the corners and midpoints between corners.

  When a color is needed, the algorithm first finds the correct cube and then compares with all the colors in the list for that cube.

  example: `colors=Image.Colortable(img)->cubicles();`

  algorithm time: between O[m] and O[m * n], where n is numbers of colors and m is number of pixels

  The arguments can be heavy trimmed for the usage of your colortable; a large number (10×10×10 or bigger) of cubicles is recommended when you use the colortable repeatedly, since the calculation takes much more time than usage.

  recommended values:

      image size  setup
      100×100     cubicles(4,5,4) (default)
      1000×1000   cubicles(12,12,12) (factor 2 faster than default)

  In some cases, the full method is faster.

  original | default cubicles, 16 colors | accuracy=200

Parameter `r`
Parameter `g`
Parameter `b`

  Size, ie how much the colorspace is divided. Note that the size of each cubicle is at least about 8b, and that it takes time to calculate them. The number of cubicles are `r*g*b`, and default is 4,5,4, ie 80 cubicles. This works good for 200±100 colors.

Parameter `accuracy`

  Accuracy when checking sides of cubicles. Default is 16. A value of 1 gives complete accuracy, ie cubicle() method gives exactly the same result as full(), but takes (in worst case) 16× the time to calculate.

Returns

  the object being called

Note

  this method doesn't figure out the cubicles, this is done on the first use of the colortable.

  Not applicable to colorcube types of colortable.