I wanted to find the type of an image as a part of upload script I am working on.

instead of having to use a module that is not pre-installed with perl or a module that requires some libraries to be installed on the server, I used this method.

sub imgtype {
    my $file  = shift;
    my %types = (
        'BMP'    => qr/^BM/,
        'GIF'    => qr/^GIF8[79]a/,
        'JPEG'    => qr/^\xFF\xD8/,
        'PNG'    => qr/^\x89PNG\x0d\x0a\x1a\x0a/,
        'PPM'    => qr/^P[1-6]/,
        'SVG'    => qr/^<\?xml/,
        'TIFF'    => qr/^MM\x00\x2a|^II\x2a\x00/,
        'XBM'    => qr/^#define\s+/,
        'XPM'    => qr/(^\/\* XPM \*\/)|(static\s+char\s+\*\w+\[\]\s*=
+\s*{\s*"\d+)/,
        );        
    if (-e $file ) {
        open(my $fh, '<', $file) or die $!;
        read($fh,my $head,11);
        close($fh);
        
        while ( my ($type,$match) = each %types ) {            
            if ( $head=~m/$match/ ) {
                return $type;                
            }
        }
        return undef;
       }else{
           return undef;
       }
}

[download]

You can use it to check against a hash of allowed file types like this

my %ALLOWED = ('GIF' => 1 ,'JPEG' => 1 );
# can be called like this 
my $Type = imgtype('some/location/image');
if ( defined $Type && $ALLOWED{$Type} ) {
   # process image
}else{
   # delete it or do whatever you want with it
}

[download]

In reply to How do I find the type of an image? by ahmad

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