proc read_png_comments {file} {
set fh [open $file r]
fconfigure $fh -encoding binary -translation binary -eofchar {}
if {[read $fh 8] != "\x89PNG\r\n\x1a\n"} { close $fh; return }
set text {}
while {[set r [read $fh 8]] != ""} {
binary scan $r Ia4 len type
set r [read $fh $len]
if {[string length $r] != $len} { close $fh; return }
if {$type == "tEXt"} {
lappend text [split $r \x00]
} elseif {$type == "iTXt"} {
set f [string first \x00 $r]
set keyword [string range $r 0 [expr {$f - 1}]]
set r [string range $r [expr {$f + 1}] end]
binary scan $r cc comp method
set r [split [string range $r 2 end] \x00]
if {$comp == 0} {
eval lappend text [list $keyword] [lrange $r 0 2]
}
}
seek $fh 4 current
}
close $fh
return $text
}Currently only supports uncompressed comments. Todo: add inflate support.
Returns a list where each element is a comment.
Each comment is itself a list. a plain text comment consists of 2 elements: the human readable keyword, and the text data. a unicode (internationl) comment is 4 elements: the human readable keyword, the langauge identifier, the translated keyword, and the unicode text data.
--AF