Reorganise image manipulation to separate integral image parts

Also unify everything else under preproc/

Note that the UsefulImg interface should be used by the main
functions, to simplify things, but this hasn't been done yet.

1 files changed, 95 insertions, 0 deletions

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
+}