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// Copyright 2019 Nick White.
// Use of this source code is governed by the GPLv3
// license that can be found in the LICENSE file.
// preproc runs binarisation and wipe preprocessing on an image
package main
// TODO: come up with a way to set a good ksize automatically
import (
"flag"
"fmt"
"image"
"image/draw"
_ "image/jpeg"
"image/png"
"log"
"os"
"rescribe.xyz/preproc"
)
// TODO: do more testing to see how good this assumption is
func autowsize(bounds image.Rectangle) int {
return bounds.Dx() / 60
}
func main() {
flag.Usage = func() {
fmt.Fprintf(os.Stderr, "Usage: preproc [-bt bintype] [-bw winsize] [-k num] [-m minperc] [-nowipe] [-wt wipethresh] [-ws wipesize] inimg outimg\n")
fmt.Fprintf(os.Stderr, "Binarize and preprocess an image\n")
flag.PrintDefaults()
}
binwsize := flag.Int("bw", 0, "Window size for sauvola binarization algorithm. Set automatically based on resolution if not set.")
ksize := flag.Float64("k", 0.5, "K for sauvola binarization algorithm. This controls the overall threshold level. Set it lower for very light text (try 0.1 or 0.2).")
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.")
nowipe := flag.Bool("nowipe", false, "Disable wiping completely.")
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()
if flag.NArg() < 2 {
flag.Usage()
os.Exit(1)
}
f, err := os.Open(flag.Arg(0))
defer f.Close()
if err != nil {
log.Fatalf("Could not open file %s: %v\n", flag.Arg(0), err)
}
img, _, err := image.Decode(f)
if err != nil {
log.Fatalf("Could not decode image: %v\n", err)
}
b := img.Bounds()
gray := image.NewGray(image.Rect(0, 0, b.Dx(), b.Dy()))
draw.Draw(gray, b, img, b.Min, draw.Src)
if *binwsize == 0 {
*binwsize = autowsize(b)
}
if *binwsize%2 == 0 {
*binwsize++
}
log.Print("Binarising")
var clean, threshimg image.Image
threshimg = preproc.IntegralSauvola(gray, *ksize, *binwsize)
if *btype == "zeroinv" {
threshimg, err = preproc.BinToZeroInv(threshimg.(*image.Gray), img.(*image.RGBA))
if err != nil {
log.Fatal(err)
}
}
if !*nowipe {
log.Print("Wiping sides")
clean = preproc.Wipe(threshimg.(*image.Gray), *wipewsize, *thresh, *min)
} else {
clean = threshimg
}
f, err = os.Create(flag.Arg(1))
if err != nil {
log.Fatalf("Could not create file %s: %v\n", flag.Arg(1), err)
}
defer f.Close()
err = png.Encode(f, clean)
if err != nil {
log.Fatalf("Could not encode image: %v\n", err)
}
}
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