Re: Convert Hue[] to RGBColor[] and backwards
- To: mathgroup at smc.vnet.net
- Subject: [mg103459] Re: Convert Hue[] to RGBColor[] and backwards
- From: "Alexander Elkins" <alexander_elkins at hotmail.com>
- Date: Wed, 23 Sep 2009 07:23:54 -0400 (EDT)
- References: <h97msg$7fi$1@smc.vnet.net>
?ToColor
ToColor[color, form] converts color to form if form is GrayLevel, RGBColor
or CMYKColor.
Otherwise form[color] is evaluated and the result is expected to be a valid
color directive.
In both v6 and v7 form can also be Hue. For example:
In[1]:= ToColor[Hue[0.1333333, 0.625, 0.8], RGBColor]
Out[1]= RGBColor[0.8, 0.7, 0.3]
In[2]:= ToColor[RGBColor[0.8, 0.7, 0.3], Hue]
Out[2]= Hue[0.133333, 0.625, 0.8]
Of course it is possible to roll one's own ToHue function:
In[3]:= ToHue[color_RGBColor] := Module[{rgb, m, n}, rgb = Clip[#, {0, 1}] &
/@ color;
m = Max @@ rgb + 0.; n = Min @@ rgb;
If[m == n, Hue[0., 0., m],
Hue[Function[{r, g, b},
Which[r == m, Mod[(g - b)/(m - n), 6], g == m, (b - r)/(m - n) + 2,
True, (r - g)/(m - n) + 4]/6] @@ rgb, 1 - n/m, m]]];
In[4]:= ToHue[RGBColor[0.8, 0.7, 0.3]]
Out[4]= Hue[0.133333, 0.625, 0.8]
- Alexander Elkins
"Bob Hanlon" <hanlonr at cox.net> wrote in message
news:h97msg$7fi$1 at smc.vnet.net...
>
> In v7 there is ColorConvert
>
> Table[ColorConvert[Hue[h], "RGBColor"], {h, 0, 1, 0.1}]
>
>
{RGBColor[1.,0.,0.],RGBColor[1.,0.6,0.],RGBColor[0.8,1.,0.],RGBColor[0.2,1.,
0.],RGBColor[0.,1.,0.4],RGBColor[0.,1.,1.],RGBColor[0.,0.4,1.],RGBColor[0.2,
0.,1.],RGBColor[0.8,0.,1.],RGBColor[1.,0.,0.6],RGBColor[1.,0.,0.]}
>
> ColorConvert[#, "Hue"] & /@ %
>
>
{Hue[0.,1.,1.],Hue[0.1,1.,1.],Hue[0.2,1.,1.],Hue[0.3,1.,1.],Hue[0.4,1.,1.],H
ue[0.5,1.,1.],Hue[0.6,1.,1.],Hue[0.7,1.,1.],Hue[0.8,1.,1.],Hue[0.9,1.,1.],Hu
e[0.,1.,1.]}
>
> As can be seen, the conversions are somewhat approximate.
>
>
> Bob Hanlon
>
> ---- Alexey Popkov <lehin.p at gmail.com> wrote:
>
> =============
> Hello,
> I have not found in the Documentation any information on relation
> between Hue[] and RGBColor[] representations of color. How can I
> convert one to another?
>
>
>
>
> --
>
> Bob Hanlon
>
>