comment on

I usually use something like this to generate colors for sections of histogram or pie charts.

sub getColor
{

    my $index = shift;         # Numerical index (integer from 0 to ..
+.)
    my @color;                 # Color components
    my @hue_matrix = (
        #
        #   R    G    B   Component to modify(0=R, 1=G, 2=B)
        #   |    |    |    |
        #   V    V    V    V    Add or subtract the offset
        #                       |     from (r,g,b) triplet
        #                       V
        [ 255,   0,   0,   2,   1 ],    # Sector 1   R   -> R+B
        [ 255,   0, 255,   0,  -1 ],    # Sector 2   R+B -> B
        [   0,   0, 255,   1,   1 ],    # ...        B   -> Cyan
        [   0, 255, 255,   2,  -1 ],    # ...        Cyan-> G
        [   0, 255,   0,   0,   1 ],    # ...        ...
        [ 255, 255,   0,   1,  -1 ],
        [ 255,   0,   0,   2,   1 ]
    );

    # Select a "spectrum sector", according to my hue matrix
    my $sector = $hue_matrix[ int($index / 42) % @hue_matrix ];

    # Calculate an offset to be applied to starting color
    my $offset = ($index % 42) * 6;

    @color = @$sector[0..2];

    # Modify selected component to generate a "continuous gradient" 
    $color[$sector->[3]] += ($sector->[4] > 0 ? $offset : -$offset);

    return(@color);
}

# Generate visually distinct colors...
print '<HTML><BODY>', "\n";

# How much distinct you decide with this factor
my $distinct_factor = 10;

for( 1 .. 30 ) 
{
    printf( 
        "<TABLE BGCOLOR=#%02X%02X%02X><TR><TD>" . '&nbsp;' x 20 . "</T
+D></TR></TABLE>\n",
        getColor($distinct_factor * $_)
    );
}
print '</BODY></HTML>';

# Or you can choose getColor() parameter at random...
[download]

The final result is:

... that of course is not perfect, but adjusting the $distinct_factor can provide satisfying results.

Update: Sorry, it was missing the last piece of code...

In reply to Re: Generating Visually Distinct Colors by cosimo
in thread Generating Visually Distinct Colors by japhy

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


Problems? Is your data what you think it is?
	PerlMonks