http://www.perlmonks.org?node_id=146130


in reply to On-demand single-pixel GIFs

I worked out a slighlty modified version of the great and really useful code above. I added support for 3 hex colors and changed default behavior to exit if no $rgb is matched. 
use strict;

my($rgb) = $ENV{PATH_INFO} =~ m|/([0-9A-F]+)(?:\.gif)?$|i;

grep {length $rgb == $_} (3, 6) || exit;

$rgb = join '', map { $_ x 2 } $rgb =~ /./g if length( $rgb ) == 3;

my $gif = pack("H*",
               '47494638396101000100B30000' . $rgb .
               'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' .
               'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' .
               'FFFFFFFFFFFFFFFFFFFFFFFFFF2C0000' .
               '0000010001000004021044003B'
              );

binmode(STDOUT);
print "Content-type: image/gif\r\n";
print "Content-length: ", length($gif), "\r\n";
print "\r\n";
print $gif;

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$|=$_='1g2i1u1l2i4e2n0k',map{print"\7",chop;select$,,$,,$,,$_/7}m{..}g

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Output a GIF file with Perl, set width, height and color
by true (Pilgrim) on Oct 15, 2002 at 22:49 UTC
    Here's another take on the same idea.
    I often find myself wanting to output
    temporary color spacer gif's for html design
    and layout purposes.
    Adjust the width, height and color of
    a gif file and output without an image module (ie ImageMagick, GD).
    #!/usr/bin/perl -w
# this script outputs a gif 
# set color, width, and height
use strict;

&printGIF("0000FF","33","10");
######################################
sub printGIF{
my $color = $_[0];
my $WH = sprintf("%lX",$_[1]);
my $HH = sprintf("%lX",$_[2]);
$color =~ s/(..)(..)(..)/$1\|$2\|$3/;
my($RH,$GH,$BH)=split(/\|/,$color);
print STDOUT "Content-type:image/gif\n\n";
my @gif=(
"47", "49", "46", "38", "37", "61", "$WH", "00", 
"$HH", "00", "A1", "01", "00", "$RH", "$GH", "$BH",
"FF", "FF", "FF", "00", "00", "00", "00", "00", 
"00", "21", "F9", "04", "05", "00", "00", "01", 
"00", "2C", "00", "00", "00", "00", "$WH", "00", 
"$HH", "00", "40", "02", "$HH", "84", "8F", "A9", 
"CB", "ED", "0F", "A3", "9C", "B4", "DA", "8B", 
"B3", "DE", "9C", "17", "00", "3B"
);
binmode (STDOUT); # if needed
foreach my $bit(@gif){
my $bita = hex($bit);
$bita = pack("C",$bita);
print STDOUT $bita;
}
}#################################### end printGIF

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