basic jpeg to flac converter

#!/usr/bin/perl -w

### WARNING, arguments are not sufficiently sanitised for untrusted use.
### Requires ImageMagick's 'identify' and the Unix 'file' command

use MIME::Base64;

my $ARGPROBS=0;
my $inimg;
my $outname;
my $desc="";
my $type=0;

while (my $arg = shift @ARGV) {
    if ($arg eq "-i") {
    if (@ARGV < 1) {
        print "$arg requires an argument\n";
        $ARGPROBS=1;
    }
    else {
        $inimg = shift @ARGV;
    }
    }
    elsif ($arg eq "-o") {
    if (@ARGV < 1) {
        print "$arg requires an argument\n";
        $ARGPROBS=1;
    }
    else {
        $outname = shift @ARGV;
    }
    }
    elsif ($arg eq "-desc") {
    if (@ARGV < 1) {
        print "$arg requires an argument\n";
        $ARGPROBS=1;
    }
    else {
        $desc = shift @ARGV;
    }
    }
    elsif ($arg eq "-type") {
    if (@ARGV < 1) {
        print "$arg requires an argument\n";
        $ARGPROBS=1;
    }
    else {
        $type = shift @ARGV;
    }
    }
    else {
    print "$arg not recognised\n";
    $ARGPROBS=1;
    }
}

if (! defined $inimg ) {
    print "Need an input image\n";
    $ARGPROBS=1;
}

if (! defined $outname ) {
    print "Need an output name\n";
    $ARGPROBS=1;
}
elsif ( -e $outname ) {
    print "$outname already exists\n";
    $ARGPROBS=1;
}

if ( $type !~ /^\d+$/ || $type > 20 ) {
    # Regex doesn't allow <0
    print "Type must be in range [0:20]\n";
    $ARGPROBS=1;
}

if ($ARGPROBS) {
    exit 1;
}

my %blockinfo = (
    type => $type,
    mime => "",
    desc => $desc,
    width     =>0,
    height    =>0,
    depth     =>0,
    palette   =>0,
    imagesize =>0
    );

if ( ! -f $inimg ) {
    print "Couldn't find $inimg\n";
    exit 1;
}
my $mimeinfo= `file --mime-type -b $inimg`;
chomp $mimeinfo;
if ( $mimeinfo ne "image/jpeg" ) {
    print "Got MIME info '$mimeinfo' for $inimg, stopping\n";
    exit 1;
}
else {
    $blockinfo{depth}=24;
}
$blockinfo{mime} = $mimeinfo;

my $imggeom= `identify -format %G $inimg`;
chomp $imggeom;
if ( ! defined $imggeom || $imggeom !~ /^(\d+)x(\d+)$/ ) {
    print "Failed getting image geometry for $inimg\n";
    exit 1;
}
$blockinfo{width}  = $1;
$blockinfo{height} = $2;

open FILE, "<", "$inimg" or die $!;
binmode FILE;

my $imgcontents;
my $size=0;
my $chunksize=200*1024;
while ( ! eof(FILE) ) {
    my $read = read FILE, $imgcontents, $chunksize, $size;
    $size += $read;
}
$blockinfo{imagesize}=$size;

if ($blockinfo{imagesize} < 1) {
    print "Couldn't read $inimg\n";
    exit 1;
}
close FILE;

$blockinfo{mimelength}=length ($blockinfo{mime});
$blockinfo{desclength}=length ($blockinfo{desc});

my $packformat = sprintf "(L[2]A[%d]LA[%d]L[5]a[%d])>",
    $blockinfo{mimelength},
    $blockinfo{desclength},
    $blockinfo{imagesize};

my $block = pack (
    $packformat,
    $blockinfo{type},       #32bit
    $blockinfo{mimelength}, #32bit
    $blockinfo{mime},
    $blockinfo{desclength}, #32bit
    $blockinfo{desc},
    $blockinfo{width},      #32bit
    $blockinfo{height},     #32bit
    $blockinfo{depth},      #32bit
    $blockinfo{palette},    #32bit
    $blockinfo{imagesize},  #32bit
    $imgcontents
    );

for my $key (keys %blockinfo ) {
    print "$key $blockinfo{$key}\n"
}


my $encoded = encode_base64( $block, "" );

if ( ! open (OUT, ">", $outname)
     ||
     ! print OUT "$encoded\n"
     ||
     ! close OUT
    )
{
    print "Error writing to $outname\n";
}