DPI support and detection

diff --git a/scan2pages.sh b/scan2pages.sh
index 45f6215..995c5a6 100755 (executable)
--- a/scan2pages.sh
+++ b/scan2pages.sh
@@ -8,6 +8,7 @@ each with only one page.
 OPTIONS:
        -v: Be verbose.
        -d depth: Use given depth. Default is 1. Unpaper can only handle up to 8.
+       -D dpi: Use given DPI. Colour scans on library scanners are usually 300, bw 400. 
        -s: skip masking/trimming. Overrides -m.
        -f: Forceably redo everything.
        -p: Forceably redo pdf conversion. Implies options below, equivalent to -f.
@@ -34,15 +35,20 @@ forceclean=
 convertflags=
 unpaperflags=
 depthflags="-depth 1"
+dpi=
 skipmask=
+verbose=
 while getopts 'vd:sfpmuc' OPTION
 do
        case $OPTION in
-       v)  convertflags="$convertflags -verbose"
+       v)      verbose=1
+               convertflags="$convertflags -verbose"
                unpaperflags="$unpaperflags -v --time"
                ;;
        d)      depthflags="-depth $OPTARG"
                ;;
+       D)      dpi=$OPTARG
+               ;;
        s)      skipmask=1;
                ;;
        f)      forcepdf=1; forcemask=1; forceunpaper=1; forceclean=1
@@ -88,6 +94,23 @@ pages=$(awk '$1 ~ "%%Pages" {print $2}' $dscname)
 echo "Got $pages page(s)."
 rm $dscname
 
+# guess at DPI, unless it's been set
+# the scans do not seem to accurately reflect their resolution.
+if [[ "$dpi" = "" ]]; then
+       # %k gives the number of colours/shades in the image.
+       # 2 for b/w, and the scanner seems to default to 400 dpi for that
+       # 256 for greyscale, which has to be selected manually (so I'm assuming 300 for no good reason)
+       # 31564 for colour, which defaults to 300
+       if [[ $( convert $file[0] -format "%k" info: || exit 1 ) == 2 ]]; then
+               dpi=400;
+       else
+               dpi=300
+       fi
+       if [[ $verbose == 1 ]]; then
+               echo "DPI guessed at $dpi."
+       fi
+fi
+
 # process pages 1 by 1 to avoid convert gobbling all the memory
 for pg in `$my_seq 1 $pages`; do
        echo "Processing page $pg."
@@ -97,7 +120,7 @@ for pg in `$my_seq 1 $pages`; do
        # convert from pdf
        origpnm=$dir/pg-${pgn}.pnm
        if [[ ! $([ -e $origpnm ]) || $forcepdf ]]; then
-               convert $convertflags $depthflags -density 300 $file[$(expr $pg - 1)] \
+               convert $convertflags $depthflags -density $dpi $file[$(expr $pg - 1)] \
                        $origpnm || exit 1
        fi;