#!/bin/sh -u
#
# Construct a wallpaper image by resizing a source image and padding.
# Pulled from rootbg and updated to use GraphicsMagick.
# Writes new image to a persistent cache in PNG format and prints the pathname.
#	- Cameron Simpson <cs@zip.com.au> 11sep2003
#

: ${BG:=black}
: ${TMPDIR:=/tmp}
: ${WALLPAPER_SHADE:=''}
: ${XINERAMA:=''}
: ${X11_COMPOSITE:=''}

gm=gm
[ -n "${PREFER_IMAGEMAGICK:-}" ] && gm=

cmd=`basename "$0"`
usage="Usage: $cmd [-g geom] [-bg bg-colour] [-sh shade] imagefiles...
        -g geom Use this target geometry instead of the display pixel size.
        -bg bg-colour
                Background colour to use for padding. Default is black,
                overridding by the envvar \$BG.
        -sh shading
                Shade (dim) the wallpaper to this percentage of full brightness.
                Default 100 on \$X11_COMPOSITE displays and 50 on others.
                Overridden by the envvar \$WALLPAPER_SHADE."

badopts=

geom=
shade=$WALLPAPER_SHADE

while [ $# -gt 0 ]
do
  case "$1" in
    -bg)BG=$2; shift ;;
    -sh)shade=$2; shift ;;
    -g)	geom=$2; shift ;;
    --)	shift; break ;;
    -?*)echo "$cmd: unrecognised option: $1" >&2; badopts=1 ;;
    *)	break ;;
  esac
  shift
done

if [ $# = 0 ]
then
  echo "$cmd: missing imagefiles" >&2
  badopts=1
fi

[ $badopts ] && { echo "$usage" >&2; exit 2; }

set -ue

if [ -z "$shade" ]
then
  if [ $X11_COMPOSITE ]
  then  shade=100
  else  shade=50
  fi
fi

if [ $# = 1 ]
then
  # replicate, one per monitor
  imagefile=$1
  set --
  for width in $X11_MONITOR_WIDTHS
  do set -- ${1+"$@"} "$imagefile"
  done
fi

##########################################
# Multiple images - assemble into montage.
if [ $# -gt 1 ]
then
    wide=0
    for width in $X11_MONITOR_WIDTHS
    do
      wide=`expr $wide + $width`
    done
    append="$gm convert +append"  ## -resize '${wide}x${X11_Y}'"
    n=0
    for width in $X11_MONITOR_WIDTHS
    do
      n=`expr $n + 1`
      eval "imagefile=\$$n"
      newimage=`X11_MONITOR_WIDTHS=$width "$0" -sh 100 "$imagefile"`
      append="$append '$newimage'"
    done
    tmpf=$TMPDIR/$cmd$$.png
    eval "$append 'png:$tmpf'"
    imagefile=`filecache "$tmpf"`
    rm "$tmpf"
    exec ls -d -- "$imagefile"
fi

##########################################
# Single image - scale to fit.
imagefile=$1
shift

bgx=`set -- $X11_MONITOR_WIDTHS; echo "$1"`
bgy=$X11_Y

# if stdin-ish name, fetch and convert to PNG
case "$imagefile" in
  X:*|-|*:-|\|* | http://* | ftp://* )
    imagefile=`fileof "$imagefile"` || exit 1
    imagefile=`pngof  "$imagefile"` || exit 1
    ;;
esac

# get image size
ix= iy=
eval `imsize-gm "$imagefile" | awk '{print "ix="$1 " iy="$2}'`
[ -n "$ix" -a -n "$iy" ] \
	|| { echo "$cmd: can't deduce source image size" >&2; exit 1; }

convname=pngof
set -- $gm convert "$imagefile"

convname=$convname/sh$shade
if [ "x$shade" != x100 ]
then
  ## -modulate does the wrong thing ## set "$@" -modulate "$shade"
  case "$shade" in
    [0-9])	mulshade=0.0$shade ;;
    [0-9][0-9]*)mulshade=0.$shade ;;
    *)		echo "$cmd: upsupported shade \"$shade\", expected 0-99" >&2
		exit 1
		;;
  esac
  set "$@" \
      -normalize \
      -operator red Multiply "$mulshade" \
      -operator green Multiply "$mulshade" \
      -operator blue Multiply "$mulshade"
fi

convname=$convname/${bgx}x${bgy}
bx=0 by=0
if [ "x${bgx}x${bgy}" != "x${ix}x${iy}" ]
then
  # must rescale

  # compute width of borders
  awkf="BEGIN { ix=$ix; iy=$iy; bgx=$bgx; bgy=$bgy
       "'       w=bgx; h=bgy
	      }
	END   { if (ix > bgx || iy > bgy)
		  # too big - shrink
		  if (ix/bgx > iy/bgy)
		    # shrink X more than Y
		    h=int(iy * (bgx/ix))
		  else
		    # shrink Y more than X
		    w=int(ix * (bgy/iy))
		else
		# smaller image - scale up
		if (bgx/ix < bgy/iy)
		  # scale X less - use that
		  h=iy*bgx/ix
		else
		  # scale Y less
		  w=ix*bgy/iy

		w+=w%2
		h+=h%2
		bx=int((bgx-w)/2)
		by=int((bgy-h)/2)
		print "bx="bx " by="by
	      }'

  eval `awk "$awkf" </dev/null`

  set "$@" -geometry "${bgx}x${bgy}"
fi

convname=$convname/pad-${bx}x${by}-$BG
if [ "$bx" -gt 0 -o "$by" -gt 0 ]
then
    set "$@" -bordercolor "$BG" -border "${bx}x${by}"
fi

exec convof -C "$convname" -discard "$imagefile" "$@" -quality 100 png:-