proc read_jpg_comments {file} {
 #: returns a list containing all the comments found in ''file''
    set fh [open $file r]
    fconfigure $fh -encoding binary -translation binary -eofchar {}
    if {[read $fh 2] != "\xFF\xD8"} { close $fh; return }
    set comments {}

    while {[read $fh 1] == "\xFF"} {
        binary scan [read $fh 3] aS type len
        set pos [tell $fh]
        if {$type == "\xFE"} {
            lappend comments [read $fh [expr $len - 2]]
        }
        seek $fh [expr {$pos + $len - 2}] start
    }
    return $comments
 }

 # Test:
  catch { console show }
  puts [ read_jpg_comments "pic.jpg" ]