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### Re: Generating Visually Distinct Colors

by cosimo (Hermit)
 on Mar 23, 2005 at 12:18 UTC ( #441747=note: print w/replies, xml ) Need Help??

in reply to Generating Visually Distinct Colors

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...

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...

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