Continuo da qui, copio dal Reference Manual, PDF scaricabile da qui, sono a p.829.

`palette`

Default value: ** color**.

** palette** indicates how to map gray levels onto color components. It works together with option enhanced3d in 3D graphics, who associates every point of a surfaces to a real number or gray level. It also works with gray images. With

**, levels are transformed into colors.**

`palette`

There are two ways for defining these transformations.

First, palette can be a vector of length three with components ranging from ** -36** to

**; each value is an index for a formula mapping the levels onto red, green and blue colors, respectively:**

`+36`

** 0: 0 1: 0.5 2: 1
3: x 4: x^2 5: x^3
6: x^4 7: sqrt(x) 8: sqrt(sqrt(x))
9: sin(90x) 10: cos(90x) 11: |x-0.5|
12: (2x-1)^2 13: sin(180x) 14: |cos(180x)|
15: sin(360x) 16: cos(360x) 17: |sin(360x)|
18: |cos(360x)| 19: |sin(720x)| 20: |cos(720x)|
21: 3x 22: 3x-1 23: 3x-2
24: |3x-1| 25: |3x-2| 26: (3x-1)/2
27: (3x-2)/2 28: |(3x-1)/2| 29: |(3x-2)/2|
30: x/0.32-0.78125 31: 2*x-0.84 32: 4x;1;-2x+1.84;x/0.08-11.5
33: |2*x - 0.5| 34: 2*x 35: 2*x - 0.5
36: 2*x - 1**

negative numbers mean negative colour component. ** palette = gray** and

**are short cuts for**

`palette = color`

**and**

`palette = [3,3,3]`

**, respectively.**

`palette = [7,5,15]`

Second, ** palette** can be a user defined lookup table. In this case, the format for building a lookup table of length

**is**

`n`

**, where**

`palette=[color_1, color_2, ..., color_n]`

**is a well formed**

`color_i`

**(see option**

`color`

**) such that**

`color`

**is assigned to the lowest gray level and**

`color_1`

**to the highest. The rest of colors are interpolated.**

`color_n`

Since this is a global graphics option, its position in the scene description does not matter.

It works together with option ** enhanced3d** in 3D graphics.

`(%i1) `**draw3d(
enhanced3d = [z-x+2*y, x, y, z],
palette = [32, -8, 17],
explicit(20*exp(-x^2-y^2)-10, x, -3, 3, y, -3, 3))$**

It also works with gray images.

`(%i2) `**im: apply(
'matrix,
makelist(makelist(random(200), i, 1, 30), i, 1, 30))$**
(%i3) */* palette = color, default */*
draw2d(image(im, 0, 0, 30, 30))$

`(%i4) `**draw2d(palette = gray, image(im, 0, 0, 30, 30))$**

`(%i5) `**draw2d(palette = [15, 20, -4],
colorbox = false,
image(im, 0, 0, 30, 30))$**

** palette** can be a user defined lookup table. In this example, low values of

**are colored in red, and higher values in yellow.**

`x`

`(%i6) `**draw3d(
palette = [red, blue, yellow],
enhanced3d = x,
explicit(x^2+y^2, x, -1, 1, y, -1, 1))$**

See also ** colorbox** and

**.**

`enhanced3d`

`point_size`

Default value: ** 1**.

** point_size** sets the size for plotted points. It must be a non negative number. This option has no effect when graphic option

**is set to**

`point_type`

**.**

`dot`

This option affects the graphic object points in either ** gr2d** and

**.**

`gr3d`

`(%i7) `**draw2d(points(makelist([random(20), random(50)], k, 1, 10)),
point_size = 5,
points(makelist(k, k, 1, 20), makelist(random(30), k, 1, 20)))$**

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