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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.
package preproc
import (
"errors"
"image"
"math"
)
type SummableImage interface {
image.Image
Sum(r image.Rectangle) uint64
}
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 - 1
if miny < b.Min.Y {
miny = b.Min.Y
}
minx := x - step - 1
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
}
// BinToZeroInv converts a binary thresholded image to a zero inverse
// binary thresholded image
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
}
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