#!/usr/local/bin/perl
#
# this is flip.pl
#
# written by Matthew Conroy (doctormatt "at" madandmoonly.com) 
#
# December 1999
#
# do whatever you want to with this program; if you find it
# useful or make improvements I'd love to hear about it
#

print "This is flipbook.pl.\n\n";
### get starting string
print"starting string: ";
$start_string=<STDIN>;
chop($start_string);
$length_start_string = length($start_string);

### get ending string
print("ending string: ");
$end_string = <STDIN>;
chop($end_string);
# note: ending string might not have same length as starting string (due to spaces)
print "\n";
print "The script will now list the initial position of each letter.\n";
print "If that letter only appears once in the ending string, then its\n";
print "ending position is determined; if the letter appears more than\n";
print "once, you will be asked to choose from among the possible ending\n";
print "positions for the letter.   A letter in parenthesis following a \n";
print "position indicates that another of the same letter is in that \n";
print "position initially.\n\n";
### determine/get permutation: the position in the final
### string corresonding to each letter of the starting string
print "initial position / letter / ending position\n";
for($i=0; $i<$length_start_string; ++$i) {
   $letter = substr($start_string,$i,1);
   local @letter_positions;
   if ($letter !~ /\s/) { ### do this if the letter's not a space
      for($j=0; $j < length($end_string); ++$j) {
         push @letter_positions, $j if ((substr($end_string,$j,1) eq $letter)
            && (not $used_positions{$j})); 
      }
      if (scalar(@letter_positions)==0) {
         print "The letter $letter doesn't appear in the ending string!";
         exit;
      }
      elsif (scalar(@letter_positions)==1) {
         print $i," ",$letter," ",$letter_positions[0],"\n";
         $end_pos[$i] = $letter_positions[0];
         $used_positions{$end_pos[$i]} = 1;
      }
      else { ### more than one of $letter in $end_string
         print $i," ",$letter," (";
         foreach(@letter_positions) {
            $lp = $_;
            unless ($used_positions{$lp}) {
               print " ",$lp;
               if (substr($start_string,$lp,1) eq $letter)  {
                  print "($letter)";
               }
            }
         }
         print ") ? ";
         $position_choice = <STDIN>;
         chop($position_choice);
         $end_pos[$i] = $position_choice;  
         $used_positions{$end_pos[$i]}=1;
      }
   }
}


### get number of frames
print"number of frames: ";
$num_frames=<STDIN>;
chop($num_frames);

### ask if frame number wanted
print "\nYou can choose to have the frame number \n";
print "printed in the lower left corner of each frame.\n";
print"This can be helpful if the frames get mixed up after\n";
print "cutting them from the pages.\n\n";
print "print frame number on each frame? ";
$query = <STDIN>;
if ($query =~ /^y/i) {
   $print_frame_number =1;
}
else {
   $print_frame_number =0;
}

### ask if separate page for each frame
print "\nWhen you have the final version, and want to print\n";
print "the frames to paper, you should print on as few pages\n";
print "as possible.  However, to preview the animation of the\n";
print "flipbook, you should give each frame its own page,\n";
print "so that you can step through the pages in your DVI\n";
print "viewer, and see the animation.\n\n";
print "Each frame on its own page? ";
$query = <STDIN>;
if ($query =~ /^y/i) {
   $separate_pages = 1;
}
else {
   $separate_pages = 0;
}

### ask for output file name
print "\nOutput file name (default is flip.tex):";
$query = <STDIN>;
chop($query);
if ($query !~ /\w/) {
   $out_filename = "flip.tex";
}
else {
   $out_filename = $query;
}

###
### Do it
###

print "\nHere we go...\n";

### some settings
$latex_font = "\\ttfamily";

$letter_width = 3;
$latex_letter_size = "\\tiny";

# for tiny, width=3 works well

$box_width=200;
#$box_width = ($length_start_string + 1)*$letter_width*1.1;
$box_height=75;
#$box_height = $box_width;
$enclosing_box = 1; ### 1=yes, 0=no
$x_shift = $box_width - $letter_width*(max($length_start_string,length($end_string))+3) ;
$y_shift = $box_height/2 - $letter_width/2;


### create coordinates for spline -
### what we have here is the signed width and height
### of the 'frame' which defines the spline
### which is the path for each letter
for ($i=0; $i < $length_start_string; ++$i) {
   $width[$i] = $letter_width * ($end_pos[$i]-$i);
   $height[$i] = $width[$i];
   push @heights,abs($height[$i]); 
   $initial_x[$i] = $letter_width * $i;
   $final_x[$i] = $letter_width * $end_pos[$i];
}

if (max(@heights)>0.5*$box_height) {
   $scaling_factor = 0.5*$box_height/max(@heights);
   for ($i=0; $i < $length_start_string; ++$i) {
      $height[$i] *= $scaling_factor;
   }
}

### create the LaTeX file
open(OUT,">$out_filename") || die;

# making LaTeX header
print OUT "\\documentclass[11pt]{report}\n";
print OUT "\\pagestyle{empty}\n";
print OUT "\\addtolength{\\oddsidemargin}{-1.5in}\n";
print OUT "\\addtolength{\\evensidemargin}{-1.5in}\n";
print OUT "\\addtolength{\\textwidth}{2.5in}\n";
print OUT "\\addtolength{\\topmargin}{-1.0in}\n";
print OUT "\\addtolength{\\textheight}{2.0in}\n";
print OUT "\\begin{document}\n";
print OUT "$latex_font\n"; ## use fixed width font
print OUT "$latex_letter_size\n"; ### use a little smaller text

### do the frames
for ($frame=1; $frame<=$num_frames; ++$frame) {
   $t = ($frame-1)/($num_frames-1);
   print  "  Frame $frame  \n";
   print OUT "\\begin{picture}($box_width,$box_height)(0,0)\n";
   if ($enclosing_box) {
      print OUT "\\put(0,0){\\line(0,1){$box_height}}\n";
      print OUT "\\put(0,0){\\line(1,0){$box_width}}\n";
      print OUT "\\put(0,$box_height){\\line(1,0){$box_width}}\n";
      print OUT "\\put($box_width,0){\\line(0,1){$box_height}}\n";
      
     
      $box_height_sub = $box_height-2;
      $box_width_sub = $box_width-2;
      print OUT "\\put(2,0){\\line(0,1){$box_height}}\n";
      print OUT "\\put(0,2){\\line(1,0){$box_width}}\n";
      print OUT "\\put(0,$box_height_sub){\\line(1,0){$box_width}}\n";
      print OUT "\\put($box_width_sub,0){\\line(0,1){$box_height}}\n";

       if ($print_frame_number) {
         print OUT "\\put(4,4){$frame}\n";
       }

   }
   ### calculate coordinates for each letter, and print it
   for ($character=0; $character<$length_start_string; ++$character) {
      $letter = substr($start_string,$character,1);
      $x = $x_shift + &cubic($t,$initial_x[$character],$initial_x[$character],
          $final_x[$character], $final_x[$character]);
      $y = $y_shift + 
         + &cubic($t,0,$height[$character],$height[$character],0);                  
      #print $letter," ",$x," ",$y,"\n";
      $x = int $x;
      $y = int $y;

      ### put the letter in the TeX file
      print OUT "\\put($x,$y){$letter}\n";

   } ### end for (character)
   
   ### end the picture environment
   print OUT "\\end{picture}\n\\hspace{0.25in}\n";

   ### if it was an even frame, start a new "line"
   print OUT "\\bigskip\n\n" if (($frame % 2)==0);
   
   ### if $separate pages is true, start a new page
   print OUT "\\clearpage\n\n" if ($separate_pages);

} ### end for (frame)



# make final statement in LaTeX file
print OUT "\\end{document}\n";

print "Done!\n";

###############################################################################

####################################
#
# Subroutines
#
####################################

sub cubic {
       local $t = @_[0];
       local $z1 = @_[1],$z2 = @_[2],$z3 = @_[3],$z4 = @_[4];
       #print "... $z1 $z2 $z3 $z3 \n";
       return((1-$t)**3*$z1 + 3*(1-$t)**2*$t*$z2 + 3*(1-$t)*($t**2)*$z3+($t**3)*$z4);
}

sub min {
    my $min = shift(@_);
    foreach $foo (@_) { 
       $min = $foo if $foo<$min;
    }
    return $min;
}

sub max {
    my $max = shift(@_);
    foreach $foo (@_) { 
       $max = $foo if $foo>$max;
    }
    return $max;
}

sub abs {
    if ($_>=0) {
       return($_);
	}
    else {
       return(-$_);
    }
}