18 files changed, 351 insertions, 51 deletions

diff --git a/preproc/cmd/binarize/main.go b/preproc/cmd/binarize/main.go
new file mode 100644
index 0000000..c274f9c
--- /dev/null
+++ b/preproc/cmd/binarize/main.go
@@ -0,0 +1,78 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"image"
+	"image/draw"
+	_ "image/jpeg"
+	"image/png"
+	"log"
+	"os"
+
+	"rescribe.xyz/go.git/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: binarize [-k num] [-t type] [-w num] inimg outimg\n")
+		flag.PrintDefaults()
+	}
+	wsize := flag.Int("w", 0, "Window size for sauvola algorithm. Set automatically based on resolution if not set.")
+	ksize := flag.Float64("k", 0.5, "K for sauvola algorithm. This controls the overall threshold level. Set it lower for very light text (try 0.1 or 0.2).")
+	btype := flag.String("t", "binary", "Type of threshold. binary or zeroinv are currently implemented.")
+	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 *wsize == 0 {
+		*wsize = autowsize(b)
+		log.Printf("Set window size to %d\n", *wsize)
+	}
+
+	if *wsize % 2 == 0 {
+		*wsize++
+	}
+
+	// TODO: come up with a way to set a good ksize automatically
+
+	var thresh image.Image
+	thresh = preproc.IntegralSauvola(gray, *ksize, *wsize)
+
+	if *btype == "zeroinv" {
+		thresh, err = preproc.BinToZeroInv(thresh.(*image.Gray), img.(*image.RGBA))
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	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, thresh)
+	if err != nil {
+		log.Fatalf("Could not encode image: %v\n", err)
+	}
+}
diff --git a/preproc/helpers_test.go b/preproc/helpers_test.go
new file mode 100644
index 0000000..326b59d
--- /dev/null
+++ b/preproc/helpers_test.go
@@ -0,0 +1,56 @@
+package preproc
+
+// TODO: add different pages as test cases
+// TODO: test non integral img version
+
+import (
+	"flag"
+	"image"
+	"image/draw"
+	"image/png"
+	"os"
+)
+
+var update = flag.Bool("update", false, "update golden files")
+
+func decode(s string) (*image.Gray, error) {
+	f, err := os.Open(s)
+	defer f.Close()
+	if err != nil {
+		return nil, err
+	}
+	img, err := png.Decode(f)
+	if err != nil {
+		return nil, err
+	}
+	b := img.Bounds()
+	gray := image.NewGray(image.Rect(0, 0, b.Dx(), b.Dy()))
+	draw.Draw(gray, b, img, b.Min, draw.Src)
+	return gray, nil
+}
+
+func imgsequal(img1 *image.Gray, img2 *image.Gray) bool {
+	b := img1.Bounds()
+	if !b.Eq(img2.Bounds()) {
+		return false
+	}
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			r0, g0, b0, a0 := img1.At(x, y).RGBA()
+			r1, g1, b1, a1 := img2.At(x, y).RGBA()
+			if r0 != r1 {
+				return false
+			}
+			if g0 != g1 {
+				return false
+			}
+			if b0 != b1 {
+				return false
+			}
+			if a0 != a1 {
+				return false
+			}
+		}
+	}
+	return true
+}
diff --git a/preproc/sauvola.go b/preproc/sauvola.go
new file mode 100644
index 0000000..e93ea81
--- /dev/null
+++ b/preproc/sauvola.go
@@ -0,0 +1,55 @@
+package preproc
+
+import (
+	"image"
+	"image/color"
+
+	"rescribe.xyz/go.git/integralimg"
+)
+
+// Implements Sauvola's algorithm for text binarization, see paper
+// "Adaptive document image binarization" (2000)
+func Sauvola(img *image.Gray, ksize float64, windowsize int) *image.Gray {
+	b := img.Bounds()
+	new := image.NewGray(b)
+
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			window := surrounding(img, x, y, windowsize)
+			m, dev := meanstddev(window)
+			threshold := m * (1 + ksize * ((dev / 128) - 1))
+			if img.GrayAt(x, y).Y < uint8(threshold) {
+				new.SetGray(x, y, color.Gray{0})
+			} else {
+				new.SetGray(x, y, color.Gray{255})
+			}
+		}
+	}
+
+	return new
+}
+
+// Implements Sauvola's algorithm using Integral Images, see paper
+// "Efficient Implementation of Local Adaptive Thresholding Techniques Using Integral Images"
+// and
+// https://stackoverflow.com/questions/13110733/computing-image-integral
+func IntegralSauvola(img *image.Gray, ksize float64, windowsize int) *image.Gray {
+	b := img.Bounds()
+	new := image.NewGray(b)
+
+	integrals := integralimg.ToAllIntegralImg(img)
+
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			m, dev := integrals.MeanStdDevWindow(x, y, windowsize)
+			threshold := m * (1 + ksize * ((dev / 128) - 1))
+			if img.GrayAt(x, y).Y < uint8(threshold) {
+				new.SetGray(x, y, color.Gray{0})
+			} else {
+				new.SetGray(x, y, color.Gray{255})
+			}
+		}
+	}
+
+	return new
+}
diff --git a/preproc/sauvola_test.go b/preproc/sauvola_test.go
new file mode 100644
index 0000000..1397a4f
--- /dev/null
+++ b/preproc/sauvola_test.go
@@ -0,0 +1,62 @@
+package preproc
+
+import (
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"testing"
+)
+
+func TestBinarization(t *testing.T) {
+	cases := []struct {
+		name string
+		orig string
+		golden string
+		ksize float64
+		wsize int
+	}{
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.5_w41.png", 0.5, 41},
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.5_w19.png", 0.5, 19},
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.3_w19.png", 0.3, 19},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.5_w41.png", 0.5, 41},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.5_w19.png", 0.5, 19},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.3_w19.png", 0.3, 19},
+	}
+
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("%s_%0.1f_%d", c.name, c.ksize, c.wsize), func(t *testing.T) {
+			var actual *image.Gray
+			orig, err := decode(c.orig)
+			if err != nil {
+				t.Fatalf("Could not open file %s: %v\n", c.orig, err)
+			}
+			switch c.name {
+			case "integralsauvola":
+				actual = IntegralSauvola(orig, c.ksize, c.wsize)
+			case "sauvola":
+				actual = Sauvola(orig, c.ksize, c.wsize)
+			default:
+				t.Fatalf("No method %s\n", c.name)
+			}
+			if *update {
+				f, err := os.Create(c.golden)
+				defer f.Close()
+				if err != nil {
+					t.Fatalf("Could not open file %s to update: %v\n", c.golden, err)
+				}
+				err = png.Encode(f, actual)
+				if err != nil {
+					t.Fatalf("Could not encode update of %s: %v\n", c.golden, err)
+				}
+			}
+			golden, err := decode(c.golden)
+			if err != nil {
+				t.Fatalf("Could not open file %s: %v\n", c.golden, err)
+			}
+			if ! imgsequal(golden, actual) {
+				t.Errorf("Binarized %s differs to %s\n", c.orig, c.golden)
+			}
+		})
+	}
+}
diff --git a/preproc/testdata/pg1.png b/preproc/testdata/pg1.png
index c7c4249..2bcc4b1 100644
--- a/preproc/testdata/pg1.png
+++ b/preproc/testdata/pg1.png
diff --git a/preproc/testdata/pg1_integralsauvola_k0.3_w19.png b/preproc/testdata/pg1_integralsauvola_k0.3_w19.png
new file mode 100644
index 0000000..bdf5712
--- /dev/null
+++ b/preproc/testdata/pg1_integralsauvola_k0.3_w19.png
diff --git a/preproc/testdata/pg1_integralsauvola_k0.5_w19.png b/preproc/testdata/pg1_integralsauvola_k0.5_w19.png
new file mode 100644
index 0000000..5db2d9a
--- /dev/null
+++ b/preproc/testdata/pg1_integralsauvola_k0.5_w19.png
diff --git a/preproc/testdata/pg1_integralsauvola_k0.5_w41.png b/preproc/testdata/pg1_integralsauvola_k0.5_w41.png
new file mode 100644
index 0000000..050d037
--- /dev/null
+++ b/preproc/testdata/pg1_integralsauvola_k0.5_w41.png
diff --git a/preproc/testdata/pg1_sauvola_k0.3_w19.png b/preproc/testdata/pg1_sauvola_k0.3_w19.png
new file mode 100644
index 0000000..bcd595f
--- /dev/null
+++ b/preproc/testdata/pg1_sauvola_k0.3_w19.png
diff --git a/preproc/testdata/pg1_sauvola_k0.5_w19.png b/preproc/testdata/pg1_sauvola_k0.5_w19.png
new file mode 100644
index 0000000..8de596c
--- /dev/null
+++ b/preproc/testdata/pg1_sauvola_k0.5_w19.png
diff --git a/preproc/testdata/pg1_sauvola_k0.5_w41.png b/preproc/testdata/pg1_sauvola_k0.5_w41.png
new file mode 100644
index 0000000..b8f50e0
--- /dev/null
+++ b/preproc/testdata/pg1_sauvola_k0.5_w41.png
diff --git a/preproc/testdata/pg2.png b/preproc/testdata/pg2.png
new file mode 100644
index 0000000..c7c4249
--- /dev/null
+++ b/preproc/testdata/pg2.png
diff --git a/preproc/testdata/pg1_integralwipesides_t0.02_w5.png b/preproc/testdata/pg2_integralwipesides_t0.02_w5.png
index 6b4ccb2..6b4ccb2 100644
--- a/preproc/testdata/pg1_integralwipesides_t0.02_w5.png
+++ b/preproc/testdata/pg2_integralwipesides_t0.02_w5.png
diff --git a/preproc/testdata/pg1_integralwipesides_t0.05_w25.png b/preproc/testdata/pg2_integralwipesides_t0.05_w25.png
index 39dc88d..39dc88d 100644
--- a/preproc/testdata/pg1_integralwipesides_t0.05_w25.png
+++ b/preproc/testdata/pg2_integralwipesides_t0.05_w25.png
diff --git a/preproc/testdata/pg1_integralwipesides_t0.05_w5.png b/preproc/testdata/pg2_integralwipesides_t0.05_w5.png
index 50df855..50df855 100644
--- a/preproc/testdata/pg1_integralwipesides_t0.05_w5.png
+++ b/preproc/testdata/pg2_integralwipesides_t0.05_w5.png
diff --git a/preproc/util.go b/preproc/util.go
new file mode 100644
index 0000000..5f8a9f1
--- /dev/null
+++ b/preproc/util.go
@@ -0,0 +1,95 @@
+package preproc
+
+import (
+	"errors"
+	"image"
+	"math"
+)
+
+// TODO: name better; maybe verb, x-er
+// TODO: implement these for regular image, and use them to make
+//       image functions generic for integral and non- images
+type UsefulImg interface {
+	MeanWindow()
+	MeanStdDevWindow()
+}
+
+func mean(i []int) float64 {
+	sum := 0
+	for _, n := range i {
+		sum += n
+	}
+	return float64(sum) / float64(len(i))
+}
+
+func stddev(i []int) float64 {
+	m := mean(i)
+
+	var sum float64
+	for _, n := range i {
+		sum += (float64(n) - m) * (float64(n) - m)
+	}
+	variance := sum / float64(len(i) - 1)
+	return math.Sqrt(variance)
+}
+
+func meanstddev(i []int) (float64, float64) {
+	m := mean(i)
+
+	var sum float64
+	for _, n := range i {
+		sum += (float64(n) - m) * (float64(n) - m)
+	}
+	variance := float64(sum) / float64(len(i) - 1)
+	return m, math.Sqrt(variance)
+}
+
+// gets the pixel values surrounding a point in the image
+func surrounding(img *image.Gray, x int, y int, size int) []int {
+	b := img.Bounds()
+	step := size / 2
+
+	miny := y - step
+	if miny < b.Min.Y {
+		miny = b.Min.Y
+	}
+	minx := x - step
+	if minx < b.Min.X {
+		minx = b.Min.X
+	}
+	maxy := y + step
+	if maxy > b.Max.Y {
+		maxy = b.Max.Y
+	}
+	maxx := x + step
+	if maxx > b.Max.X {
+		maxx = b.Max.X
+	}
+
+	var s []int
+	for yi := miny; yi <= maxy; yi++ {
+		for xi := minx; xi <= maxx; xi++ {
+			s = append(s, int(img.GrayAt(xi, yi).Y))
+		}
+	}
+	return s
+}
+
+func BinToZeroInv(bin *image.Gray, orig *image.RGBA) (*image.RGBA, error) {
+	b := bin.Bounds()
+	if ! b.Eq(orig.Bounds()) {
+		return orig, errors.New("bin and orig images need to be the same dimensions")
+	}
+	newimg := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			if bin.GrayAt(x, y).Y == 255 {
+				newimg.Set(x, y, bin.GrayAt(x, y))
+			} else {
+				newimg.Set(x, y, orig.At(x, y))
+			}
+		}
+	}
+
+	return newimg, nil
+}
diff --git a/preproc/wipesides.go b/preproc/wipesides.go
index c773054..4806e93 100644
--- a/preproc/wipesides.go
+++ b/preproc/wipesides.go
@@ -7,7 +7,7 @@ import (
 	"image"
 	"image/color"
 
-	"rescribe.xyz/go.git/binarize"
+	"rescribe.xyz/go.git/integralimg"
 )
 
 type IntWindow struct { // TODO: put this in its own package
@@ -126,7 +126,7 @@ func wipesides(img *image.Gray, lowedge int, highedge int) *image.Gray {
 // wipe fills the sections of image which fall outside the content
 // area with white
 func Wipe(img *image.Gray, wsize int, thresh float64) *image.Gray {
-	integral := binarize.Integralimg(img)
+	integral := integralimg.ToIntegralImg(img)
 	lowedge, highedge := findedges(integral, wsize, thresh)
 	return wipesides(img, lowedge, highedge)
 }
diff --git a/preproc/wipesides_test.go b/preproc/wipesides_test.go
index b0ada4e..f66f39b 100644
--- a/preproc/wipesides_test.go
+++ b/preproc/wipesides_test.go
@@ -4,59 +4,13 @@ package preproc
 // TODO: test non integral img version
 
 import (
-	"flag"
 	"fmt"
 	"image"
-	"image/draw"
 	"image/png"
 	"os"
 	"testing"
 )
 
-var update = flag.Bool("update", false, "update golden files")
-
-func decode(s string) (*image.Gray, error) {
-	f, err := os.Open(s)
-	defer f.Close()
-	if err != nil {
-		return nil, err
-	}
-	img, err := png.Decode(f)
-	if err != nil {
-		return nil, err
-	}
-	b := img.Bounds()
-	gray := image.NewGray(image.Rect(0, 0, b.Dx(), b.Dy()))
-	draw.Draw(gray, b, img, b.Min, draw.Src)
-	return gray, nil
-}
-
-func imgsequal(img1 *image.Gray, img2 *image.Gray) bool {
-	b := img1.Bounds()
-	if !b.Eq(img2.Bounds()) {
-		return false
-	}
-	for y := b.Min.Y; y < b.Max.Y; y++ {
-		for x := b.Min.X; x < b.Max.X; x++ {
-			r0, g0, b0, a0 := img1.At(x, y).RGBA()
-			r1, g1, b1, a1 := img2.At(x, y).RGBA()
-			if r0 != r1 {
-				return false
-			}
-			if g0 != g1 {
-				return false
-			}
-			if b0 != b1 {
-				return false
-			}
-			if a0 != a1 {
-				return false
-			}
-		}
-	}
-	return true
-}
-
 func TestWipeSides(t *testing.T) {
 	cases := []struct {
 		name   string
@@ -65,9 +19,9 @@ func TestWipeSides(t *testing.T) {
 		thresh float64
 		wsize  int
 	}{
-		{"integralwipesides", "testdata/pg1.png", "testdata/pg1_integralwipesides_t0.02_w5.png", 0.02, 5},
-		{"integralwipesides", "testdata/pg1.png", "testdata/pg1_integralwipesides_t0.05_w5.png", 0.05, 5},
-		{"integralwipesides", "testdata/pg1.png", "testdata/pg1_integralwipesides_t0.05_w25.png", 0.05, 25},
+		{"integralwipesides", "testdata/pg2.png", "testdata/pg2_integralwipesides_t0.02_w5.png", 0.02, 5},
+		{"integralwipesides", "testdata/pg2.png", "testdata/pg2_integralwipesides_t0.05_w5.png", 0.05, 5},
+		{"integralwipesides", "testdata/pg2.png", "testdata/pg2_integralwipesides_t0.05_w25.png", 0.05, 25},
 	}
 
 	for _, c := range cases {