WebProg 初心者の質問 Part3

WebProg 初心者の質問 Part3at PHP

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812:811
 03/06/03 18:19 /P4baUDR
Image::Sizeのソースから 
sub jpegsize 
{ 
    my $stream = shift; 
    my $MARKER      = "\xFF";       # Section marker. 
    my $SIZE_FIRST  = 0xC0;         # Range of segment identifier codes 
    my $SIZE_LAST   = 0xC3;         #  that hold size info. 
    my ($x, $y, $id) = (undef, undef, "could not determine JPEG size"); 
    my ($marker, $code, $length); 
    my $segheader; 
    # Dummy read to skip header ID 
    &$read_in($stream, 2); 
    while (1) 
    { 
        $length = 4; 
        $segheader = &$read_in($stream, $length); 
        # Extract the segment header. 
        ($marker, $code, $length) = unpack("a a n", $segheader);

813:811続き
 03/06/03 18:19 /P4baUDR
# Verify that it's a valid segment. 
        if ($marker ne $MARKER) 
        { 
            # Was it there? 
            $id = "JPEG marker not found"; 
            last; 
        } 
        elsif ((ord($code) >= $SIZE_FIRST) && (ord($code) <= $SIZE_LAST)) 
        { 
            # Segments that contain size info 
            $length = 5; 
            ($y, $x) = unpack("xnn", &$read_in($stream, $length)); 
            $id = 'JPG'; 
            last; 
        } 
        else 
        { 
            # Dummy read to skip over data 
            &$read_in($stream, ($length - 2)); 
        } 
    } 
    ($x, $y, $id); 
}

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