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-rw-r--r--preproc/util.go95
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
+}