I think you want to 

  sub {{
    my $ret = [ map {int} @$c ];
    ...

[download]

to stop returning floating point back to the caller. Makes for funny HTML otherwise.

Update: Actually, you're rounding too early. 
  $w = [ map {
       my $v = $f + $s*$_/$i;
       $f = $v - int($v);
       $v # not int $v
     } @$w ];
     $w->[-1] += $f;

[download]

The problem is that it works fine for linear gradients, but when you use non-linear gradients the round-off adds up and your iterator poops out before it gets to the end.

Why would you want to use a non-linear gradient? Because the (in)?famous Netscape Color Cube(TM) is a terrible thing: it lends to much emphasis to highly saturated colors, and as a result there are too few colors to represent the many subtle hues the eye is capable of distinguishing.

So what I attempted to do was to create a sinusoidal curve, peaking at 1 in the middle of the gradient and dropping to 0 at the ends. That's where I uncovered the int problem. Once I had my weight array the way I wanted it, I plugged it into the iterator, but for some reason that escapes me, I'm not seeing the behaviour I expect. The numbers should climb away quickly from first value in the interval move slowly around the midpoint, and then drop quickly down to the end value.

It may be that I have completely misunderstood what the weights' purpose. Whatever, here's the code. No, I didn't use CGI, this is a quick hack, not production code.

use constant PI => 4 * atan2(1,1);

my $intervals = 40;
my $iterlin = range( [  0,255,255] => [  0,255,  0],
    [(1) x $intervals],
    $intervals );
my $itersin = range( [  0,255,255] => [  0,255,  0],
    [ map {sin(($_/$intervals)*PI) } 0..$intervals],
    $intervals );

print qq{<html><head><title>Gradient</title></head>
<body bgcolor="#ffffff"><table>\n};

while (my ($rgb_lin, $width) = $iterlin->()) {
    my ($rgb_sin, $widthsin) = $itersin->();

    my $lin = join '', '#',
        map { sprintf '%02x',$_ } @$rgb_lin;
    my $sin = join '', '#',
        map { sprintf '%02x',$_ } @$rgb_sin;

    print qq{<tr>
<td bgcolor="$lin"><tt>$$rgb_lin[0]</tt></td>
<td bgcolor="$lin"><tt>$$rgb_lin[1]</tt></td>
<td bgcolor="$lin"><tt>$$rgb_lin[2]</tt></td>
<td bgcolor="$sin"><tt>$$rgb_sin[0]</tt></td>
<td bgcolor="$sin"><tt>$$rgb_sin[1]</tt></td>
<td bgcolor="$sin"><tt>$$rgb_sin[2]</tt></td>
</tr>};
}
print "</table></body></html>\n";

[download]

In reply to Re: RGBgradient by grinder
in thread RGBgradient by japhy

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