Add -m option to wipe to set minimum content area for wipe to proceed

If content is very light or sparse it may be better to not wipe at all
than wipe almost all of the content leaving a small strip. This is done
now by aborting the wipe if the detected content takes up less than the
minimum % of the page (default is 30%).

1 files changed, 3 insertions, 3 deletions

diff --git a/preproc/cmd/preprocmulti/main.go b/preproc/cmd/preprocmulti/main.go
index eea7ab4..947625e 100644
--- a/preproc/cmd/preprocmulti/main.go
+++ b/preproc/cmd/preprocmulti/main.go
@@ -1,7 +1,6 @@
 package main
 
 // TODO: come up with a way to set a good ksize automatically
-// TODO: add minimum size variable (default ~30%?) for wipe
 
 import (
 	"flag"
@@ -26,7 +25,7 @@ func main() {
 	ksizes := []float64{0.2, 0.3, 0.4, 0.5, 0.6}
 
 	flag.Usage = func() {
-		fmt.Fprintf(os.Stderr, "Usage: preproc [-bt bintype] [-bw winsize] [-wt wipethresh] [-ws wipesize] inimg outbase\n")
+		fmt.Fprintf(os.Stderr, "Usage: preproc [-bt bintype] [-bw winsize] [-m minperc] [-wt wipethresh] [-ws wipesize] inimg outbase\n")
 		fmt.Fprintf(os.Stderr, "Binarize and preprocess an image, with multiple binarisation levels,\n")
 		fmt.Fprintf(os.Stderr, "saving images to outbase_bin{k}.png.\n")
 		fmt.Fprintf(os.Stderr, "Binarises with these levels for k: %v.\n", ksizes)
@@ -34,6 +33,7 @@ func main() {
 	}
 	binwsize := flag.Int("bw", 0, "Window size for sauvola binarization algorithm. Set automatically based on resolution if not set.")
 	btype := flag.String("bt", "binary", "Type of binarization threshold. binary or zeroinv are currently implemented.")
+	min := flag.Int("m", 30, "Minimum percentage of the image width for the content width calculation to be considered valid.")
 	wipewsize := flag.Int("ws", 5, "Window size for wiping algorithm.")
 	thresh := flag.Float64("wt", 0.05, "Threshold for the wiping algorithm to determine the proportion of black pixels below which a window is determined to be the edge.")
 	flag.Parse()
@@ -80,7 +80,7 @@ func main() {
 		}
 
 		log.Print("Wiping sides")
-		clean := preproc.Wipe(threshimg.(*image.Gray), *wipewsize, *thresh)
+		clean := preproc.Wipe(threshimg.(*image.Gray), *wipewsize, *thresh, *min)
 
 		savefn := fmt.Sprintf("%s_bin%0.1f.png", flag.Arg(1), k)
 		log.Printf("Saving %s\n", savefn)