From 699634be83582c47075db8520ab262669990a325 Mon Sep 17 00:00:00 2001
From: Nick White <git@njw.name>
Date: Thu, 13 Feb 2020 09:04:38 +0000
Subject: Add experimental and partial splittable tool

---
 cmd/splittable/main.go | 139 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 cmd/splittable/main.go

diff --git a/cmd/splittable/main.go b/cmd/splittable/main.go
new file mode 100644
index 0000000..1029db1
--- /dev/null
+++ b/cmd/splittable/main.go
@@ -0,0 +1,139 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"image"
+	"image/draw"
+	_ "image/jpeg"
+	"image/png"
+	"log"
+	"os"
+
+	"rescribe.xyz/preproc/integralimg"
+)
+
+const usage = `Usage: splittable [-t thresh] [-w winsize] inimg outbase
+
+splittable is an experimental program to split a table into individual
+cells suitable for OCR. It does this by detecting lines. At present it
+just detects vertical lines and outputs images for each section
+between those lines.
+
+`
+
+// returns the proportion of the given window that is black pixels
+func proportion(i integralimg.I, x int, size int) float64 {
+	w := i.GetVerticalWindow(x, size)
+	return w.Proportion()
+}
+
+// findbestvline goes through every vertical line from x to x+w to
+// find the one with the lowest proportion of black pixels.
+func findbestvline(img integralimg.I, x int, w int) int {
+	var bestx int
+	var best float64
+
+	if w == 1 {
+		return x
+	}
+
+	right := x + w
+	for ; x < right; x++ {
+		prop := proportion(img, x, 1)
+		if prop > best {
+			best = prop
+			bestx = x
+		}
+	}
+
+	return bestx
+}
+
+// findvlines finds vertical lines, returning an array of x coordinates
+// for each line. It works by moving a window of wsize across the image,
+// marking each place where there is a higher proportion of black pixels
+// than thresh.
+func findvlines(img integralimg.I, wsize int, thresh float64) []int {
+	maxx := len(img[0]) - 1
+	var lines []int
+
+	for x := 0; x < maxx-wsize; x+=wsize {
+		if proportion(img, x, wsize) >= thresh {
+			l := findbestvline(img, x, wsize)
+			lines = append(lines, l)
+		}
+	}
+
+	return lines
+}
+
+func drawsection(img *image.Gray, x1 int, x2 int) *image.Gray {
+	b := img.Bounds()
+	width := x2-x1
+	new := image.NewGray(image.Rect(0, b.Min.Y, width, b.Max.Y))
+
+	for x := 0; x < width; x++ {
+		for y := b.Min.Y; y < b.Max.Y; y++ {
+			new.SetGray(x, y, img.GrayAt(x1 + x, y))
+		}
+	}
+
+	return new
+}
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintf(flag.CommandLine.Output(), usage)
+		flag.PrintDefaults()
+	}
+	thresh := flag.Float64("t", 0.85, "Threshold for the proportion of black pixels below which a window is determined to be a line. Higher means fewer lines will be found.")
+	wsize := flag.Int("w", 1, "Window size for mask finding algorithm.")
+	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)
+
+	integral := integralimg.ToIntegralImg(gray)
+	vlines := findvlines(integral, *wsize, *thresh)
+
+	for i, v := range vlines {
+		fmt.Printf("line detected at x=%d\n", v)
+
+		if i+1 >= len(vlines) {
+			break
+		}
+		section := drawsection(gray, v, vlines[i+1])
+
+		fn := fmt.Sprintf("%s-%d.png", flag.Arg(1), v)
+		f, err = os.Create(fn)
+		if err != nil {
+			log.Fatalf("Could not create file %s: %v\n", fn, err)
+		}
+		defer f.Close()
+		err := png.Encode(f, section)
+		if err != nil {
+			log.Fatalf("Could not encode image %s: %v\n", fn, err)
+		}
+	}
+
+
+	// TODO: find horizontal lines too
+	// TODO: do rotation
+	// TODO: output table cells
+	// TODO: potentially send cells straight to tesseract
+}
-- 
cgit v1.2.1-24-ge1ad