The hsb color model

[Henrik Skov Midtiby]

Hi

I wondered if it is possible to define colors in the hsv / hsb color model, when making drawings in tikz?

According to the manual (14.2 Specifying a color) the \definecolor command
only implements the rgb and gray color models, but is it possible to bypass
this limitation?

Henrik


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[Kjell Magne Fauske]

On Wed, Oct 22, 2008 at 9:33 PM, Henrik Skov Midtiby
<henrikmidtiby@...> wrote:

> Hi
>
> I wondered if it is possible to define colors in the hsv / hsb color model, when making drawings in tikz?
>
> According to the manual (14.2 Specifying a color) the \definecolor command
> only implements the rgb and gray color models, but is it possible to bypass
> this limitation?
>
> Henrik
>

If I understand the manual correctly, the limitation only applies to
plain TeX. When using LaTeX xcolor is used and I believe xcolor
supports the hsv/hsb color model.

- Kjell Magne Fauske

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[Henrik Skov Midtiby]

> If I understand the manual correctly, the limitation only applies to
> plain TeX. When using LaTeX xcolor is used and I believe xcolor
> supports the hsv/hsb color model.
I have tried the code given below, which renders badly and raises the a warning (see warning after the code snippet).

It seems that tikz doesn't implement the hsb color model. In the manual (14.2 Specifying a Color)
> Because of this, pgf emulates the xcolor package,
> though the emulation is extremely basic...

The goal for my coding is to draw the hsv color cone from this address:
http://en.wikipedia.org/wiki/Image:HSV_cone.png

Henrik

<code>
\documentclass{article}
\usepackage{xcolor}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
% Draws a yellow filled circle
\definecolor{currentcolor}{rgb}{1, 1, 0}
\draw[fill=currentcolor] (0, 0) circle (1cm);

% Draws a black filled circle (it should be red ...)
\definecolor{currentcolor}{hsb}{1, 1, 1}
\draw[fill=currentcolor] (3, 0) circle (1cm);
\end{tikzpicture}

\end{document}
</code>

<warning>
./hsvcolorcone.tex:14:Package pgfbase Error: Unsupported color model `hsb'. Sorry. \draw[fill=currentcolor] (3, 0) circle (1cm);
</warning>



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[Kjell Magne Fauske]

On Wed, Oct 22, 2008 at 11:13 PM, Henrik Skov Midtiby
<henrikmidtiby@...> wrote:

>> If I understand the manual correctly, the limitation only applies to
>> plain TeX. When using LaTeX xcolor is used and I believe xcolor
>> supports the hsv/hsb color model.
> I have tried the code given below, which renders badly and raises the a warning (see warning after the code snippet).
>
> It seems that tikz doesn't implement the hsb color model. In the manual (14.2 Specifying a Color)
>> Because of this, pgf emulates the xcolor package,
>> though the emulation is extremely basic...
>
> The goal for my coding is to draw the hsv color cone from this address:
> http://en.wikipedia.org/wiki/Image:HSV_cone.png
>
> Henrik
>
> <code>
> \documentclass{article}
> \usepackage{xcolor}
> \usepackage{tikz}
>
> \begin{document}
>
> \begin{tikzpicture}
> % Draws a yellow filled circle
> \definecolor{currentcolor}{rgb}{1, 1, 0}
> \draw[fill=currentcolor] (0, 0) circle (1cm);
>
> % Draws a black filled circle (it should be red ...)
> \definecolor{currentcolor}{hsb}{1, 1, 1}
> \draw[fill=currentcolor] (3, 0) circle (1cm);
> \end{tikzpicture}
>
> \end{document}
> </code>
>
> <warning>
> ./hsvcolorcone.tex:14:Package pgfbase Error: Unsupported color model `hsb'. Sorry. \draw[fill=currentcolor] (3, 0) circle (1cm);
> </warning>
>

You are right. A workaround is to set the target color model to rgb.
xcolor will then do the necessary conversions for you:

<code>
\documentclass{article}
\usepackage[rgb]{xcolor}%<- set target model
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
% Draws a yellow filled circle
\definecolor{currentcolor}{rgb}{1, 1, 0}
\draw[fill=currentcolor] (0, 0) circle (1cm);

% Draws a black filled circle (it should be red ...)
\foreach \x in {0,0.05,...,1.1} {
\definecolor{currentcolor}{hsb}{\x, 1, \x}
\draw[fill=currentcolor,xshift=40*\x] (3, 0) circle (1cm);
}
\end{tikzpicture}

\end{document}
</code>

- Kjell Magne Fauske

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[Henrik Skov Midtiby]

> You are right. A workaround is to set the target color model to rgb.
> xcolor will then do the necessary conversions for you:
Great! Thanks for the workaround.

Henrik

PS: My code new looks like
<code>
\documentclass{article}
\usepackage[rgb]{xcolor}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\foreach \x in {0,0.0111,...,1} {
        \definecolor{currentcolor}{hsb}{\x, 1, 1}
        \draw[draw=none, fill=currentcolor]
                (-360*\x+88:2) -- (-360*\x+88:3.8)
                -- (-360*\x+92:3.8) -- (-360*\x+92:2) -- cycle;
}
\draw [draw=none, fill=red] (90:1.5) circle (2cm);
\draw [draw=none, fill=green] (-30:1.5) circle (2cm);
\draw [draw=none, fill=blue] (210:1.5) circle (2cm);
\begin{scope} % red + green = yellow
        \clip (90:1.5) circle(2cm);
        \draw [draw=none, fill=yellow] (-30:1.5) circle (2cm);
\end{scope} % blue + red = purple
\begin{scope}
        \clip (210:1.5) circle(2cm);
        \draw [draw=none, fill=magenta] (90:1.5) circle (2cm);
\end{scope}
\begin{scope} % green + blue = cyan
        \clip (-30:1.5) circle(2cm);
        \draw [draw=none, fill=cyan] (210:1.5) circle (2cm);
\end{scope}
\begin{scope} % red + green + blue = white
        \clip (90:1.5) circle(2cm);
        \clip (210:1.5) circle(2cm);
        \draw [draw=none, fill=white] (-30:1.5) circle (2cm);
\end{scope}
\draw (0, 0) circle (3.9cm);
%\foreach \x/\y in {0/270, 30/300, 60/330, 90/0, 120/30, 150/60, 180/90, 210/120, 240/150, 270/180, 300/210, 330/240}
% \draw (\x:3.8) -- (\x:4.0) (\x:4.4) node {$\y^\circ$};
\foreach \x  in {0, 30, ..., 330}
        \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^\circ$};
\end{tikzpicture}
\end{document}
</code>


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[Kjell Magne Fauske]

On Thu, Oct 23, 2008 at 4:40 PM, Henrik Skov Midtiby
<henrikmidtiby@...> wrote:

>
>> You are right. A workaround is to set the target color model to rgb.
>> xcolor will then do the necessary conversions for you:
> Great! Thanks for the workaround.
>
> Henrik
>
> PS: My code new looks like
> <code>
> \documentclass{article}
> \usepackage[rgb]{xcolor}
> \usepackage{tikz}
>
> \begin{document}
> \begin{tikzpicture}
> \foreach \x in {0,0.0111,...,1} {
>        \definecolor{currentcolor}{hsb}{\x, 1, 1}
>        \draw[draw=none, fill=currentcolor]
>                (-360*\x+88:2) -- (-360*\x+88:3.8)
>                -- (-360*\x+92:3.8) -- (-360*\x+92:2) -- cycle;
> }
> \draw [draw=none, fill=red] (90:1.5) circle (2cm);
> \draw [draw=none, fill=green] (-30:1.5) circle (2cm);
> \draw [draw=none, fill=blue] (210:1.5) circle (2cm);
> \begin{scope} % red + green = yellow
>        \clip (90:1.5) circle(2cm);
>        \draw [draw=none, fill=yellow] (-30:1.5) circle (2cm);
> \end{scope} % blue + red = purple
> \begin{scope}
>        \clip (210:1.5) circle(2cm);
>        \draw [draw=none, fill=magenta] (90:1.5) circle (2cm);
> \end{scope}
> \begin{scope} % green + blue = cyan
>        \clip (-30:1.5) circle(2cm);
>        \draw [draw=none, fill=cyan] (210:1.5) circle (2cm);
> \end{scope}
> \begin{scope} % red + green + blue = white
>        \clip (90:1.5) circle(2cm);
>        \clip (210:1.5) circle(2cm);
>        \draw [draw=none, fill=white] (-30:1.5) circle (2cm);
> \end{scope}
> \draw (0, 0) circle (3.9cm);
> %\foreach \x/\y in {0/270, 30/300, 60/330, 90/0, 120/30, 150/60, 180/90, 210/120, 240/150, 270/180, 300/210, 330/240}
> %       \draw (\x:3.8) -- (\x:4.0) (\x:4.4) node {$\y^\circ$};
> \foreach \x  in {0, 30, ..., 330}
>        \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^\circ$};
> \end{tikzpicture}
> \end{document}
> </code>
>

Nice illustration!

For the record, PGF does support the CMY and CMYK color models. This
means that you can write:

\usepackage[cmyk]{xcolor}
\usepackage[cmy]{xcolor}

- Kjell Magne Fauske

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[Ken Starks]

This is very nice, I agree.

But I was wondering, could you achieve  something similar  using a shading
dictionary ? Yes, if you accept a linear or radial shading, I am sure. Does
Pgf/Tikz allow other kinds of shading, as allowed by the PDF standard ? It
would be nice to make the PDF engine do all the work, and it would certainly
make for a smaller file size ?    



Kjell Magne Fauske wrote:

> On Thu, Oct 23, 2008 at 4:40 PM, Henrik Skov Midtiby
> <henrikmidtiby@...> wrote:
>  
>>> You are right. A workaround is to set the target color model to rgb.
>>> xcolor will then do the necessary conversions for you:
>>>      
>> Great! Thanks for the workaround.
>>
>> Henrik
>>
>> PS: My code new looks like
>> <code>
>> \documentclass{article}
>> \usepackage[rgb]{xcolor}
>> \usepackage{tikz}
>>
>> \begin{document}
>> \begin{tikzpicture}
>> \foreach \x in {0,0.0111,...,1} {
>>        \definecolor{currentcolor}{hsb}{\x, 1, 1}
>>        \draw[draw=none, fill=currentcolor]
>>                (-360*\x+88:2) -- (-360*\x+88:3.8)
>>                -- (-360*\x+92:3.8) -- (-360*\x+92:2) -- cycle;
>> }
>> \draw [draw=none, fill=red] (90:1.5) circle (2cm);
>> \draw [draw=none, fill=green] (-30:1.5) circle (2cm);
>> \draw [draw=none, fill=blue] (210:1.5) circle (2cm);
>> \begin{scope} % red + green = yellow
>>        \clip (90:1.5) circle(2cm);
>>        \draw [draw=none, fill=yellow] (-30:1.5) circle (2cm);
>> \end{scope} % blue + red = purple
>> \begin{scope}
>>        \clip (210:1.5) circle(2cm);
>>        \draw [draw=none, fill=magenta] (90:1.5) circle (2cm);
>> \end{scope}
>> \begin{scope} % green + blue = cyan
>>        \clip (-30:1.5) circle(2cm);
>>        \draw [draw=none, fill=cyan] (210:1.5) circle (2cm);
>> \end{scope}
>> \begin{scope} % red + green + blue = white
>>        \clip (90:1.5) circle(2cm);
>>        \clip (210:1.5) circle(2cm);
>>        \draw [draw=none, fill=white] (-30:1.5) circle (2cm);
>> \end{scope}
>> \draw (0, 0) circle (3.9cm);
>> %\foreach \x/\y in {0/270, 30/300, 60/330, 90/0, 120/30, 150/60, 180/90, 210/120, 240/150, 270/180, 300/210, 330/240}
>> %       \draw (\x:3.8) -- (\x:4.0) (\x:4.4) node {$\y^\circ$};
>> \foreach \x  in {0, 30, ..., 330}
>>        \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^\circ$};
>> \end{tikzpicture}
>> \end{document}
>> </code>
>>
>>    
>
> Nice illustration!
>
> For the record, PGF does support the CMY and CMYK color models. This
> means that you can write:
>
> \usepackage[cmyk]{xcolor}
> \usepackage[cmy]{xcolor}
>
> - Kjell Magne Fauske
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
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> https://lists.sourceforge.net/lists/listinfo/pgf-users
>
>
>  

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[Till Tantau-3]

Hi!


pgf does support the following shading types of the pgf standard:

- axis shadings
- radial shadings
- functional shadings

The last type of shading can, indeed, be used to let the renderer  
produce the color circle. However, someone would have to sit down and  
write and test the necessary shading specification (would take half an  
hour, I presume). If someone has it, please post it, we can put it in  
a lib, other people might like this.


Best regards,
Till



Am 24.10.2008 um 10:12 schrieb Ken Starks:

> This is very nice, I agree.
>
> But I was wondering, could you achieve  something similar  using a  
> shading
> dictionary ? Yes, if you accept a linear or radial shading, I am  
> sure. Does
> Pgf/Tikz allow other kinds of shading, as allowed by the PDF  
> standard ? It
> would be nice to make the PDF engine do all the work, and it would  
> certainly
> make for a smaller file size ?
>
>
>
> Kjell Magne Fauske wrote:
>> On Thu, Oct 23, 2008 at 4:40 PM, Henrik Skov Midtiby
>> <henrikmidtiby@...> wrote:
>>
>>>> You are right. A workaround is to set the target color model to  
>>>> rgb.
>>>> xcolor will then do the necessary conversions for you:
>>>>
>>> Great! Thanks for the workaround.
>>>
>>> Henrik
>>>
>>> PS: My code new looks like
>>> <code>
>>> \documentclass{article}
>>> \usepackage[rgb]{xcolor}
>>> \usepackage{tikz}
>>>
>>> \begin{document}
>>> \begin{tikzpicture}
>>> \foreach \x in {0,0.0111,...,1} {
>>>       \definecolor{currentcolor}{hsb}{\x, 1, 1}
>>>       \draw[draw=none, fill=currentcolor]
>>>               (-360*\x+88:2) -- (-360*\x+88:3.8)
>>>               -- (-360*\x+92:3.8) -- (-360*\x+92:2) -- cycle;
>>> }
>>> \draw [draw=none, fill=red] (90:1.5) circle (2cm);
>>> \draw [draw=none, fill=green] (-30:1.5) circle (2cm);
>>> \draw [draw=none, fill=blue] (210:1.5) circle (2cm);
>>> \begin{scope} % red + green = yellow
>>>       \clip (90:1.5) circle(2cm);
>>>       \draw [draw=none, fill=yellow] (-30:1.5) circle (2cm);
>>> \end{scope} % blue + red = purple
>>> \begin{scope}
>>>       \clip (210:1.5) circle(2cm);
>>>       \draw [draw=none, fill=magenta] (90:1.5) circle (2cm);
>>> \end{scope}
>>> \begin{scope} % green + blue = cyan
>>>       \clip (-30:1.5) circle(2cm);
>>>       \draw [draw=none, fill=cyan] (210:1.5) circle (2cm);
>>> \end{scope}
>>> \begin{scope} % red + green + blue = white
>>>       \clip (90:1.5) circle(2cm);
>>>       \clip (210:1.5) circle(2cm);
>>>       \draw [draw=none, fill=white] (-30:1.5) circle (2cm);
>>> \end{scope}
>>> \draw (0, 0) circle (3.9cm);
>>> %\foreach \x/\y in {0/270, 30/300, 60/330, 90/0, 120/30, 150/60,  
>>> 180/90, 210/120, 240/150, 270/180, 300/210, 330/240}
>>> %       \draw (\x:3.8) -- (\x:4.0) (\x:4.4) node {$\y^\circ$};
>>> \foreach \x  in {0, 30, ..., 330}
>>>       \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^
>>> \circ$};
>>> \end{tikzpicture}
>>> \end{document}
>>> </code>
>>>
>>>
>>
>> Nice illustration!
>>
>> For the record, PGF does support the CMY and CMYK color models. This
>> means that you can write:
>>
>> \usepackage[cmyk]{xcolor}
>> \usepackage[cmy]{xcolor}
>>
>> - Kjell Magne Fauske
>>
>> -------------------------------------------------------------------------
>> This SF.Net email is sponsored by the Moblin Your Move Developer's  
>> challenge
>> Build the coolest Linux based applications with Moblin SDK & win  
>> great prizes
>> Grand prize is a trip for two to an Open Source event anywhere in  
>> the world
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>> _______________________________________________
>> pgf-users mailing list
>> pgf-users@...
>> https://lists.sourceforge.net/lists/listinfo/pgf-users
>>
>>
>>
>
>
> -------------------------------------------------------------------------
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> challenge
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> great prizes
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--
Prof. Dr. Till Tantau <tantau@...>
http://www.tcs.uni-luebeck.de


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[Ken Starks]

Hello,

Here is a version of a HSV ring in which I have used a functional shading.

The main guts of the thing contains code to turn three HSV values on
the stack into three RGB values, which I hope will be useful elsewhere.

I have tried to put in quite a bit of documentation, in terms of stack
listings  on nearly every line.

Bye for now,

Ken.

%%% code starts %%%%%%%%%%



\documentclass{article}
\usepackage[rgb]{xcolor}
\usepackage{colortbl}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}

\pgfdeclarefunctionalshading{HSVsweep}
{\pgfpoint{-2cm}{-2cm}}
{\pgfpoint{2cm}{2cm}}
{}
{ % x y
2 copy % ... x y x y
2 copy 0 eq exch 0 eq and
{ pop pop 0.0 } % silently deal with error: return arbitrary heading of
zero for origin
{atan 360.0 div} % ... x y heading;  heading being in the interval [0, 1.0]
ifelse  % because we will use it for 'Hue'
dup 360 eq { pop 0.0 }{} ifelse % if heading is 360 degrees, make it
zero instead
3 1 roll % ... heading x y
dup mul % ... heading x y*y
exch dup mul % ... heading y*y x*x
add sqrt % ... heading radius_pt (distance from origin in points)
56 div % scale it means a radius of just under 2 cm
dup 1.0 ge % BOOLEAN. ready to clamp to interval [0, 1.0]
  { pop 1.0 }{} ifelse % We shall use the scaled radius as 'Saturation'
  2.5 mul 0.25 sub % now, Radius in [0.1, 0.5] --> Saturation in [0.0,
1.0]. Saturation varies between the two radii
  1.0 % ... H S V ( with 'Value' set to literal constant of 1.0 )
  false % TEST I [ S == 1.0 ]
  { % BLOCK A [ take stack to V V V ] achromatic case
  }
  { % BLOCK B take stack to V T Q P i
    % C version to use as model:
      % H' = H * 6
      % i = floor(H')
      % f = H' - i
      % P = V * (1.0 - S)
      % Q = V * (1.0 - (S*f))
      % T = V * (1.0 - (S * (1.0 - f)))
    3 -1 roll 6.0 mul dup 4 1 roll % H' S V H'
    floor % H' S V i
    dup  5 1 roll % i H' S V i
    3 index sub neg % i H' S V f
    1.0 3 index sub % i H' S V f (1.0 - S )
    2 index mul % i H' S V f P
    6 1 roll % P i H' S V f
    dup 3 index mul neg 1.0 add % P i H' S V f ( 1.0 - (f*S))
    2 index mul % P i H' S V f Q
    7 1 roll % Q P i H' S V f
    neg 1.0 add % Q P i H' S V (1.0 - f)
    2 index mul neg 1.0  add % Q P i H' S V (1.0 - S * (1.0 - f))
    1 index mul % Q P i H' S V T
    7 2 roll % V T Q P i H' S
    pop pop % V T Q P i
    %%%
    % end of BLOCK B. The rest is just stack manipulation
    dup 0 eq % TEST II [ i == 0 ]
    { % BLOCK C [ take stack to V T P ]
    pop exch pop
    }
    { dup 1 eq % TEST III [ i == 1 ]
      { % BLOCK D [ take stack to Q V P ]
    pop exch 4 1 roll exch pop
      }
      { dup 2 eq % TEST IV [ i == 2 ]
        { % BLOCK E [ take stack to P V T ]
        pop 4 1 roll pop
        }
        { dup 3 eq % TEST V [ i == 3 ]
          { % BLOCK F [ take stack to P Q V ]
          pop exch 4 2 roll pop
          }
          { dup 4 eq % TEST VI [ i == 4 ]
            { % BLOCK G [ take stack to T P V ]
            pop exch pop 3 -1 roll
            }
            { % BLOCK H [ take stack to V P Q ]
            pop 3 1 roll exch pop
            }
            ifelse
          }
          ifelse % for V
        }
        ifelse % for IV
      }
      ifelse % for III
    }
    ifelse % for II
    % BLOCK I
  }
  ifelse % for I
  % BLOCK J
  % .. RGB at last
}

% \pgfuseshading{HSVsweep}


\begin{tikzpicture}
  % The shape is the region between two circles, centered at the origin
  % Drawn in opposite directions to allow a non-zero fill to work.
  \def\radius{3.8cm}
  \def\radiusB{1.5cm}
  \def\cveclen{0.55228475*\radius}
  \def\cveclenB{0.55228475*\radiusB}
 
  \pgfpathmoveto{\pgfpoint{\radius}{0cm}};
  \pgfpathcurveto
 
{\pgfpoint{\radius}{\cveclen}}{\pgfpoint{\cveclen}{\radius}}{\pgfpoint{0cm}{\radius}};
 
  \pgfpathcurveto
 
{\pgfpoint{-\cveclen}{\radius}}{\pgfpoint{-\radius}{\cveclen}}{\pgfpoint{-\radius}{0cm}};
 
  \pgfpathcurveto
 
{\pgfpoint{-\radius}{-\cveclen}}{\pgfpoint{-\cveclen}{-\radius}}{\pgfpoint{0cm}{-\radius}};
 
  \pgfpathcurveto
 
{\pgfpoint{\cveclen}{-\radius}}{\pgfpoint{\radius}{-\cveclen}}{\pgfpoint{\radius}{0cm}};
 
  \pgfpathmoveto{\pgfpoint{\radiusB}{0cm}};
 
  \pgfpathcurveto
 
{\pgfpoint{\radiusB}{-\cveclenB}}{\pgfpoint{\cveclenB}{-\radiusB}}{\pgfpoint{0cm}{-\radiusB}};
 
 
  \pgfpathcurveto
 
{\pgfpoint{-\cveclenB}{-\radiusB}}{\pgfpoint{-\radiusB}{-\cveclenB}}{\pgfpoint{-\radiusB}{0cm}};
 
  \pgfpathcurveto
 
{\pgfpoint{-\radiusB}{\cveclenB}}{\pgfpoint{-\cveclenB}{\radiusB}}{\pgfpoint{0cm}{\radiusB}};
 
  \pgfpathcurveto
 
{\pgfpoint{\cveclenB}{\radiusB}}{\pgfpoint{\radiusB}{\cveclenB}}{\pgfpoint{\radiusB}{0cm}};
  \pgfclosepath;
\pgfshadepath{HSVsweep}{0}
\pgfusepath{stroke}


\foreach \x  in {0, 30, ..., 330}
    \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^\circ$};
\end{tikzpicture}



\end{document}


See:
James D FOLEY et al
"Computer Graphics, Principals and Practice"
2nd edition
ISBN 0-204-84840-6

Page 593. Figure 13.34
"Algorithm for converting from HSV to RGB color space"
(This is C. I had to convert it to Postscript. Mostly
lots of nasty stack manipulation)


Till Tantau wrote:

> Hi!
>
>
> pgf does support the following shading types of the pgf standard:
>
> - axis shadings
> - radial shadings
> - functional shadings
>
> The last type of shading can, indeed, be used to let the renderer
> produce the color circle. However, someone would have to sit down and
> write and test the necessary shading specification (would take half an
> hour, I presume). If someone has it, please post it, we can put it in
> a lib, other people might like this.
>
>
> Best regards,
> Till
>
>
>
> Am 24.10.2008 um 10:12 schrieb Ken Starks:
>
>> This is very nice, I agree.
>>
>> But I was wondering, could you achieve  something similar  using a
>> shading
>> dictionary ? Yes, if you accept a linear or radial shading, I am
>> sure. Does
>> Pgf/Tikz allow other kinds of shading, as allowed by the PDF standard
>> ? It
>> would be nice to make the PDF engine do all the work, and it would
>> certainly
>> make for a smaller file size ?
>>
>>
>

<snip>
> --
> Prof. Dr. Till Tantau <tantau@...>
> http://www.tcs.uni-luebeck.de
>
>
>


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[Ken Starks]

Sorry,

Copy and Paste made it not work.
It seems the code got mucked up somewhere in the email software. I
expect the long lines were chopped or something.

Here is hoping it will work as an attached file. I've just sent it to
myself as a private email, and it seemed OK.

Can someone reply to tell me if it worked for them ?

Ken Starks wrote:

> Hello,
>
> Here is a version of a HSV ring in which I have used a functional shading.
>
> The main guts of the thing contains code to turn three HSV values on
> the stack into three RGB values, which I hope will be useful elsewhere.
>
> I have tried to put in quite a bit of documentation, in terms of stack
> listings  on nearly every line.
>
> Bye for now,
>
> Ken.
>
>  

> Till Tantau wrote:
>  
>> Hi!
>>
>>
>> pgf does support the following shading types of the pgf standard:
>>
>> - axis shadings
>> - radial shadings
>> - functional shadings
>>
>> The last type of shading can, indeed, be used to let the renderer
>> produce the color circle. However, someone would have to sit down and
>> write and test the necessary shading specification (would take half an
>> hour, I presume). If someone has it, please post it, we can put it in
>> a lib, other people might like this.
>>
>>
>> Best regards,
>> Till
>>
>>
>>
>> Am 24.10.2008 um 10:12 schrieb Ken Starks:
>>
>>    
>>> This is very nice, I agree.
>>>
>>> But I was wondering, could you achieve  something similar  using a
>>> shading
>>> dictionary ? Yes, if you accept a linear or radial shading, I am
>>> sure. Does
>>> Pgf/Tikz allow other kinds of shading, as allowed by the PDF standard
>>> ? It
>>> would be nice to make the PDF engine do all the work, and it would
>>> certainly
>>> make for a smaller file size ?
>>>
>>>
>>>      
> <snip>
>  
>> --
>> Prof. Dr. Till Tantau <tantau@...>
>> http://www.tcs.uni-luebeck.de
>>
>>
>>
>>    
>
>
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>
>
>  

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[Alain Matthes-2]

Le 26 oct. 08 à 14:04, Ken Starks a écrit :

> Sorry,
>
> Copy and Paste made it not work.
> It seems the code got mucked up somewhere in the email software. I
> expect the long lines were chopped or something.
>
> Here is hoping it will work as an attached file. I've just sent it to
> myself as a private email, and it seemed OK.
>
> Can someone reply to tell me if it worked for them ?

Hi,

It's fine if I  modify the lines that begin  with

\pgfpathmoveto

{ ...etc ...}

with \pgfpathmoveto{..} after it's correct !

Best Regards

Alain



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[Ken Starks]

Thanks Alain,

It seems that the problem is indeed line-lengths.

Here is a copy that should work without editing ( I hope)

%%%%%%%%%%%%
\documentclass{article}
\usepackage[rgb]{xcolor}
\usepackage{colortbl}
\usepackage{tikz}
\usetikzlibrary{calc}
\newcommand{\pgp}{\pgfpoint}

\begin{document}
\pgfdeclarefunctionalshading{HSVsweep}
{\pgp{-2cm}{-2cm}}
{\pgp{2cm}{2cm}}
{}
{ % x y
2 copy % ... x y x y
2 copy 0 eq exch 0 eq and
{ pop pop 0.0 } % silently deal with error: return
               % arbitrary heading of zero for origin
{atan 360.0 div} % ... x y heading;  heading being in
                %the interval [0, 1.0]
ifelse  % because we will use it for 'Hue'
dup 360 eq { pop 0.0 }{} ifelse % if heading is 360
                               %degrees, make it zero instead
3 1 roll % ... heading x y
dup mul % ... heading x y*y
exch dup mul % ... heading y*y x*x
add sqrt % ... heading ra_pt (distance from origin in points)
56 div % scale it means a ra of just under 2 cm
dup 1.0 ge % BOOLEAN. ready to clamp to interval [0, 1.0]
{ pop 1.0 }{} ifelse % We shall use the scaled ra as 'Saturation'
2.5 mul 0.25 sub % now, Ra in [0.1, 0.5] --> Saturation
                % in [0.0, 1.0]. Saturation varies between the two radii
1.0 % ... H S V ( with 'Value' set to literal constant of 1.0 )
false % TEST I [ S == 1.0 ]
{ % BLOCK A [ take stack to V V V ] achromatic case
}
{ % BLOCK B take stack to V T Q P i
   % C version to use as model:
     % H' = H * 6
     % i = floor(H')
     % f = H' - i
     % P = V * (1.0 - S)
     % Q = V * (1.0 - (S*f))
     % T = V * (1.0 - (S * (1.0 - f)))
   3 -1 roll 6.0 mul dup 4 1 roll % H' S V H'
   floor % H' S V i
   dup  5 1 roll % i H' S V i
   3 index sub neg % i H' S V f
   1.0 3 index sub % i H' S V f (1.0 - S )
   2 index mul % i H' S V f P
   6 1 roll % P i H' S V f
   dup 3 index mul neg 1.0 add % P i H' S V f ( 1.0 - (f*S))
   2 index mul % P i H' S V f Q
   7 1 roll % Q P i H' S V f
   neg 1.0 add % Q P i H' S V (1.0 - f)
   2 index mul neg 1.0  add % Q P i H' S V (1.0 - S * (1.0 - f))
   1 index mul % Q P i H' S V T
   7 2 roll % V T Q P i H' S
   pop pop % V T Q P i
   %%%
   % end of BLOCK B. The rest is just stack manipulation
   dup 0 eq % TEST II [ i == 0 ]
   { % BLOCK C [ take stack to V T P ]
   pop exch pop
   }
   { dup 1 eq % TEST III [ i == 1 ]
     { % BLOCK D [ take stack to Q V P ]
   pop exch 4 1 roll exch pop
     }
     { dup 2 eq % TEST IV [ i == 2 ]
       { % BLOCK E [ take stack to P V T ]
       pop 4 1 roll pop
       }
       { dup 3 eq % TEST V [ i == 3 ]
         { % BLOCK F [ take stack to P Q V ]
         pop exch 4 2 roll pop
         }
         { dup 4 eq % TEST VI [ i == 4 ]
           { % BLOCK G [ take stack to T P V ]
           pop exch pop 3 -1 roll
           }
           { % BLOCK H [ take stack to V P Q ]
           pop 3 1 roll exch pop
           }
           ifelse
         }
         ifelse % for V
       }
       ifelse % for IV
     }
     ifelse % for III
   }
   ifelse % for II
   % BLOCK I
}
ifelse % for I
% BLOCK J
% .. RGB at last
}
% \pgfuseshading{HSVsweep}
\begin{tikzpicture}
% The shape is the region between two circles, centered
% at the origin
% Drawn in opposite directions to allow a non-zero
% fill to work.
\def\ra{3.8cm}
\def\raB{1.5cm}
\def\cv{0.55228475*\ra}
\def\cvB{0.55228475*\raB}
\pgfpathmoveto{\pgp{\ra}{0cm}};
\pgfpathcurveto
{\pgp{\ra}{\cv}}{\pgp{\cv}{\ra}}{\pgp{0cm}{\ra}};
\pgfpathcurveto
{\pgp{-\cv}{\ra}}{\pgp{-\ra}{\cv}}{\pgp{-\ra}{0cm}};
\pgfpathcurveto
{\pgp{-\ra}{-\cv}}{\pgp{-\cv}{-\ra}}{\pgp{0cm}{-\ra}};
\pgfpathcurveto
{\pgp{\cv}{-\ra}}{\pgp{\ra}{-\cv}}{\pgp{\ra}{0cm}};
\pgfpathmoveto{\pgp{\raB}{0cm}};
\pgfpathcurveto
{\pgp{\raB}{-\cvB}}{\pgp{\cvB}{-\raB}}{\pgp{0cm}{-\raB}};
\pgfpathcurveto
{\pgp{-\cvB}{-\raB}}{\pgp{-\raB}{-\cvB}}{\pgp{-\raB}{0cm}};
\pgfpathcurveto
{\pgp{-\raB}{\cvB}}{\pgp{-\cvB}{\raB}}{\pgp{0cm}{\raB}};
\pgfpathcurveto
{\pgp{\cvB}{\raB}}{\pgp{\raB}{\cvB}}{\pgp{\raB}{0cm}};
\pgfclosepath;
\pgfshadepath{HSVsweep}{0}
\pgfusepath{stroke}
\foreach \x  in {0, 30, ..., 330}
   \draw (-\x+90:3.8) -- (-\x+90:4.0) (-\x+90:4.4) node {$\x^\circ$};
\end{tikzpicture}
\end{document}


See:
James D FOLEY et al
"Computer Graphics, Principals and Practice"
2nd edition
ISBN 0-204-84840-6

Page 593. Figure 13.34
"Algorithm for converting from HSV to RGB color space"
(This is C. I had to convert it to Postscript. Mostly
lots of nasty stack manipulation)






%%%%%%%%%%%%

Alain Matthes wrote:

>
> Le 26 oct. 08 à 14:04, Ken Starks a écrit :
>
>> Sorry,
>>
>> Copy and Paste made it not work.
>> It seems the code got mucked up somewhere in the email software. I
>> expect the long lines were chopped or something.
>>
>> Here is hoping it will work as an attached file. I've just sent it to
>> myself as a private email, and it seemed OK.
>>
>> Can someone reply to tell me if it worked for them ?
>
>
> Hi,
>
> It's fine if I  modify the lines that begin  with
>
> \pgfpathmoveto
>
> { ...etc ...}
>
> with \pgfpathmoveto{..} after it's correct !
>
> Best Regards
>
> Alain
>
>
>
>

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[Berteun Damman]

On Sun, Oct 26, 2008 at 3:35 PM, Ken Starks <ken@...> wrote:
> Here is a copy that should work without editing ( I hope)

I'd like to add that Apples PDF viewer bugs on this shading,
apparently because of the fact the numbers are not real values
(thankfully the manual knew this). :) It's of course Apples fault, but
it can be worked around, as the manual suggests too, by adding:

 % .. RGB at last
 cvr 3 1 roll cvr 3 1 roll cvr 3 1 roll

At the end.

Berteun

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[Ken Starks]

Berteun Damman wrote:

> On Sun, Oct 26, 2008 at 3:35 PM, Ken Starks <ken@...> wrote:
>  
>> Here is a copy that should work without editing ( I hope)
>>    
>
> I'd like to add that Apples PDF viewer bugs on this shading,
> apparently because of the fact the numbers are not real values
> (thankfully the manual knew this). :) It's of course Apples fault, but
> it can be worked around, as the manual suggests too, by adding:
>
>  % .. RGB at last
>  cvr 3 1 roll cvr 3 1 roll cvr 3 1 roll
>
> At the end.
>
> Berteun
>
> -------------------------------------------------------------------------
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> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/pgf-users
>
>
>  

Thanks for that Berteun.

I was aware of this bug, but thought (mistakedly, it seems) that my  
final values
were already real. That's why I kept putting 1.0 instead of 1 in so many
places.

Oh well, you live and learn.

Thanks again and Goodbye,

Ken


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