#!/bin/sh
#
# Check if an image is black & white (bi-level)
#

MAGIC=/usr/share/misc/magic-mm

[ $# -eq 0 ] && { echo "usage: chkbw file ..." >&2; exit 1; }

for f in "$@"; do
    ts="$(file -m $MAGIC "$f")"; t="${ts#*: }"
    case "$t" in
    TIFF\ image\ data*)
	pnmcmd=tifftopnm;;
    GIF\ image\ data*)
	pnmcmd=giftoppm;;
    PNG\ image\ data*)
	pnmcmd=pngtopnm;;
    PC\ bitmap\ data*)
	pnmcmd=bmptopnm;;
    IFF\ data,\ ILBM*)
	pnmcmd=ilbmtoppm;;
    *)
	case "$1" in
	*.[Jj][Bb][Gg])
	    pnmcmd=jbgtopbm;;
	*.[Pp][Cc][Xx] | *.[Pp[Cc][Cc])
	    pnmcmd=/usr/local/netpbm/bin/pcxtoppm;;
	*)
	    echo "chkbw: Unsupported file format" >&2
	    exit 1;;
	esac
    esac
    hist=$($pnmcmd "$f" 2>/dev/null | ppmhist | wc -l)
    [ $hist -gt 4 ] && echo "$f: Not B/W" >&2
done
.