# DeAnim FilterProxy Module # Copyright (C) 2000, 2001 Bob McElrath. # See the file COPYING for redistribution and modification terms. # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA package FilterProxy::DeAnim; use strict; no strict 'subs'; use vars qw($VERSION $CONFIG); push @FilterProxy::MODULES, # add myself to FilterProxy's list of known "DeAnim"; # modules $VERSION = 0.01; $CONFIG = {}; $CONFIG->{order} = 4; $CONFIG->{mime_types} = [ # is a list of mime-types that this module "image/gif" # knows how to filter. Can contain an empty ]; # string to specify all mime-types. *logger = \&FilterProxy::logger; sub filter { # The main filtering routine. Does the dirty work. my($req) = shift; # $req is the HTTP::Request object my($res) = shift; # $res is the HTTP::Response object. my($siteconfig) = shift; if(defined $res && defined $res->content_ref) { my $oldsize = length ${$res->content_ref}; my $modified = 0; my $G = { Gifstream => ${$res->content_ref}, Offset => 0, # current parsing offset }; # gif "object" my $newgif = ''; my $readgif = sub { my $len = shift; # logger(DEBUG, "gif_read: offset=$G->{Offset} len=$len"); my $data = substr(($G->{Gifstream}), $G->{Offset}, $len); if ((my $newlen = length($data)) != $len) { logger(ERROR, "gif_read: wanted $len bytes, but could only read $newlen bytes\n"); return; } $G->{Offset} += $len; $newgif .= $data; return($data); }; # GIF89 GRAMMAR: ############### # ::= Header * Trailer(3B) # ::= Logical Screen Descriptor [Global Color Table] # ::= | # ::= [Graphic Control Extension(21F9)] # ::= | Plain Text Extension(2101) # ::= Image Descriptor(2C) [Local Color Table] Image Data # ::= Application Extension(21FF) | Comment Extension(21FE) ############### # HEADER if (length($G->{Gifstream}) < 10) { logger(ERROR, " DeAnim: gif of less than 10 bytes? Whadafuk?\n"); return; } my $header = $readgif->(6); # logger(DEBUG, " DeAnim: HEADER"); unless ($header eq "GIF89a") { return if($header eq "GIF87a"); # GIF87a's cant be animated anyway. logger(ERROR, sprintf(" expected GIF header, found %s\n", $header)); return; } # logger(DEBUG, " DeAnim: LOGICAL SCREEN"); my $ls_desc = $readgif->(7); my ($ls_size, $ls_flag, $ls_misc) = unpack("A4 C A2", $ls_desc); if ($ls_flag & 0x80) { my $size = $ls_flag & 0x07; my $bytes = 3 * 2**($size+1); # logger(DEBUG, " DeAnim: GLOBAL COLOR TABLE (OPTIONAL)"); my $global_color_table = $readgif->($bytes); } while (1) { # logger(DEBUG, " DeAnim: DATA*"); last if (substr($G->{Gifstream}, $G->{Offset}, 1) eq "\x3B"); # TRAILER my $label = $readgif->(1); last if (not $label); # EOF if ($label eq "\x21") { # EXTENSION INTRODUCER my $start_ext = $G->{Offset} - 1; # logger(DEBUG, " DeAnim: EXTENSION INTRODUCER"); $label = $readgif->(1); if ($label eq "\xFF") { # logger(DEBUG, " DeAnim: APPLICATION EXTENSION"); my $size = unpack("C", $readgif->(1)); if ($size != 11) { logger(ERROR, " DeAnim: expected application extension size==11, got $size\n"); return; } my $app_ex = $readgif->($size); while ($size = unpack("C", $readgif->(1))) { # read data sub-block(s) my $sub_block = $readgif->($size); } # $size should be zero -- the data sub-block terminator value } elsif ($label eq "\xFE") { # logger(DEBUG, " DeAnim: COMMENT EXTENSION"); while (my $size = unpack("C", $readgif->(1))) { # read data sub-block(s) my $sub_block = $readgif->($size); } # $size should be zero -- the data sub-block terminator value } elsif ($label eq "\xF9") { # logger(DEBUG, " DeAnim: GRAPHIC BLOCK/GRAPHIC CONTROL EXTENSION (OPTIONAL)"); my $size = unpack("C", $readgif->(1)); if ($size != 4) { # logger(ERROR, " DeAnim: expected graphic control extension size==4, got $size\n"); return; } my $gr_con = $readgif->($size); my $terminator = $readgif->(1); if (defined $terminator && !$terminator) { logger(ERROR, " DeAnim: expected graphic control extension terminator==0, got '$terminator'(len ", length $terminator, ", ", sprintf("%#02x", $terminator), ")\n"); return; } # we allow graphic control extensions, so don't delete them. next; } elsif ($label eq "\x01") { # logger(DEBUG, " DeAnim: PLAIN TEXT EXTENSION"); my $size = unpack("C", $readgif->(1)); if ($size != 12) { logger(ERROR, " DeAnim: expected plain text extension size==12, got $size\n"); return; } my $pl_txt_ex = $readgif->($size); while ($size = unpack("C", $readgif->(1))) { # read data sub-block(s) my $sub_block = $readgif->($size); } } else { logger(ERROR, " DeAnim: expected an extension type\n"); return; } # delete this extension my $len = length($newgif); my $delta = $G->{Offset} - $start_ext; logger(DEBUG, " DeAnim: deleting extension ($delta bytes)"); my $stuff = substr($newgif, $len - $delta, $delta); # logger(DEBUG, " ", map { sprintf("%02x", (ord($_))) } split(//,$stuff)); $newgif = substr($newgif, 0, $len - $delta); $modified = 1; next; } if ($label eq "\x2C") { # logger(DEBUG, " DeAnim: IMAGE DESCRIPTOR"); my $im_desc = $readgif->(9); my ($im_misc, $im_flag) = unpack("A8 C", $im_desc); if ($im_flag & 0x80) { # logger(DEBUG, " DeAnim: LOCAL COLOR TABLE (OPTIONAL)"); my $size = $im_flag & 0x07; my $bytes = 3 * 2**($size+1); $readgif->($bytes); # local color table } # logger(DEBUG, " DeAnim: IMAGE DATA"); my $lzw_min = $readgif->(1); while (my $size = unpack("C", $readgif->(1))) { # read data sub-block(s) my $sub_block = $readgif->($size); } # we are finished since we've extracted the first gif frame last; } else { logger(ERROR, " DeAnim: expected a table based image\n"); return; } } $newgif .= "\x3B"; # add final "trailer" if ($@) { chomp($@); logger(ERROR, " DeAnim: Error parsing GIF: $@"); logger(ERROR, " DeAnim: Current Offset: $G->{Offset}"); $G->{Offset} = $G->{Offset} - 4 if ($G->{Offset} >= 4); my $data = $readgif->(8); logger(ERROR, sprintf(" DeAnim: bytes before/after offset: %x %x %x %x / %x %x %x %x %s", unpack("C8", $data), $data)); return; # return (gif unchanged) } my $newsize = length $newgif; if($modified || $newsize != $oldsize) { $res->content($newgif); logger(DEBUG, " DeAnim: GIF was modified ($oldsize->$newsize bytes), returning new GIF.\n"); } } return; # nothing needs to be returned. } sub Config { my($req, $cgi, $siteconfig) = @_; return "It worked.\n"; }