opusmbptagで入力画像のMIMETYPEを推測する機能を追加

app/opusmbptag.sh

@@ -160,7 +160,6 @@ esac
 if ! expr x"$mime" : x'[] !"#$%&'\''()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\^_`abcdefghijklmnopqrstuvwxyz{|}~-]*$' >/dev/null
 then E invalid mime type string
 fi
-printf %s "$mime" |iconv -t us-ascii >"$tmp/mime"
 
 description_conv_arg="-t utf-8"
 case $have_description_file in
@@ -189,6 +188,17 @@ case $# in
 *) usage ;;
 esac
 
+if [ -z "$mime" ]
+then
+	determine="$(file - <"$tmp/binary")"
+	case "$determine" in
+	*JPEG*|*JFIF*) mime=image/jpeg ;;
+	*GIF*) mime=image/gif ;;
+	*PNG*) mime=image/png ;;
+	esac
+fi
+printf %s "$mime" |iconv -t us-ascii >"$tmp/mime"
+
 # generate packet
 {
 	printf METADATA_BLOCK_PICTURE=