http://qs1969.pair.com?node_id=229880


in reply to Linear Fractal Generator

Beautiful (just like the original). :) I had a few idle moments, so I sat down and cleaned it up a bit. It started out mainly as a cleanup of the rainbow palette generation (which is now in RAINBOW_PAL and calc_gradient()), but grew to a complete reorganization. It does not, I'm afraid, have the neat update-as-you-calculate effect anymore, but the upside is faster runtime - and it is pretty easy to port to a different windowing system, a console-only version that outputs a PNG via GD or any number of other output possibilities by just changing init_and_make_updater() as well as done().
#!/usr/bin/perl -w use strict; use Tk; ###### SETTINGS ###### use constant EPSILON => 6; use constant SET_NR => 0; use constant INITIAL_LINE => ([100, 240, 540, 240]); use constant POINT_SET => ( [ [ 0, 0], [ 10, 20], [ 90, -20], [100, 0], ], [ [ 0, 0], [ 50, 29], [ 50, -29], [100, 0], ], [ [ 0, 0], [ 50, 0], [ 50, 50], [ 50, 0], [100, 0], ], [ [ 0, 0], [ 30, 0], [ 50, 30], [ 70, 0], [100, 0], ], ); use constant RAINBOW_PAL => ( R => [255 => 255 => 0 => 0 => 255 => 255], G => [ 0 => 255 => 255 => 255 => 0 => 0], B => [ 0 => 0 => 255 => 255 => 255 => 0], ); ###### FUNCTIONS ###### use constant X => 0; use constant Y => 1; use constant PALETTE_GRANULARITY => 255; sub calc_gradient { my %par = @_; my @pal; for(0 .. $#{$par{R}}-1) { my $rlum = $par{R}[$_]; my $glum = $par{G}[$_]; my $blum = $par{B}[$_]; my $rinc = ($par{R}[$_ + 1] - $par{R}[$_]) / PALETTE_GRANULARI +TY; my $ginc = ($par{G}[$_ + 1] - $par{G}[$_]) / PALETTE_GRANULARI +TY; my $binc = ($par{B}[$_ + 1] - $par{B}[$_]) / PALETTE_GRANULARI +TY; push @pal, map sprintf('#%02x%02x%02x', $rlum + $rinc * $_, $glum + $ginc * $_, $blum + $binc * $_, ), 0 .. PALETTE_GRANULARITY; } return \@pal; } my @pt = map [ map $_/100, @$_], @{(POINT_SET)[SET_NR]}; sub iterate_lines { map { my ($X1, $Y1, $X2, $Y2) = @$_; (abs($Y2 - $Y1)>EPSILON or abs($X2 - $X1)>EPSILON) ? map [ $X1+($X2-$X1)*$pt[$_][X] +($Y2-$Y1)*$pt[$_][Y], $Y1+($Y2-$Y1)*$pt[$_][X] -($X2-$X1)*$pt[$_][Y], $X1+($X2-$X1)*$pt[$_+1][X] +($Y2-$Y1)*$pt[$_+1][Y], $Y1+($Y2-$Y1)*$pt[$_+1][X] -($X2-$X1)*$pt[$_+1][Y], ], 0 .. $#pt - 1 : $_; } @_ } sub init_and_make_updater { my @pal = @{+shift}; my $window = Tk::MainWindow->new; my $label = ""; $window->Label(-textvariable => \$label)->pack; my $canvas = $window->Canvas( -width => 640, -height => 480, -background => 'black', )->pack; my $lines; return sub { ($label, $lines) = @_; if(defined $lines) { my $inc = @pal / @$lines; my $idx = -$inc; $canvas->delete('all'); $canvas->createLine(@$_, -fill => $pal[$idx += $inc]) for +@$lines; } $window->update; } } sub done { MainLoop; } ###### MAIN PROGRAM ###### my $update = init_and_make_updater(calc_gradient(RAINBOW_PAL)); $update->("Initializing..."); my @lines = INITIAL_LINE; my $lines_previously = 0; my $iter = 0; until($lines_previously == @lines) { $lines_previously = @lines; $iter++; @lines = iterate_lines @lines; $update->("Iteration $iter...", \@lines); } $update->("Done."); done(\@lines);

Makeshifts last the longest.