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package main
import (
"image"
"math"
)
type integralwindow struct {
topleft uint64
topright uint64
bottomleft uint64
bottomright uint64
width int
height int
}
func integralimg(img *image.Gray) [][]uint64 {
b := img.Bounds()
var oldy, oldx, oldxy uint64
var integral [][]uint64
for y := b.Min.Y; y < b.Max.Y; y++ {
newrow := []uint64{}
for x := b.Min.X; x < b.Max.X; x++ {
oldx, oldy, oldxy = 0, 0, 0
if x > 0 {
oldx = newrow[x-1]
}
if y > 0 {
oldy = integral[y-1][x]
}
if x > 0 && y > 0 {
oldxy = integral[y-1][x-1]
}
pixel := uint64(img.GrayAt(x, y).Y)
i := pixel + oldx + oldy - oldxy
newrow = append(newrow, i)
}
integral = append(integral, newrow)
}
return integral
}
func integralimgsq(img *image.Gray) [][]uint64 {
b := img.Bounds()
var oldy, oldx, oldxy uint64
var integral [][]uint64
for y := b.Min.Y; y < b.Max.Y; y++ {
newrow := []uint64{}
for x := b.Min.X; x < b.Max.X; x++ {
oldx, oldy, oldxy = 0, 0, 0
if x > 0 {
oldx = newrow[x-1]
}
if y > 0 {
oldy = integral[y-1][x]
}
if x > 0 && y > 0 {
oldxy = integral[y-1][x-1]
}
pixel := uint64(img.GrayAt(x, y).Y)
i := pixel * pixel + oldx + oldy - oldxy
newrow = append(newrow, i)
}
integral = append(integral, newrow)
}
return integral
}
// this gets the values of the four corners of a window, which can
// be used to quickly calculate the mean of the area
func getintegralwindow(integral [][]uint64, x int, y int, size int) integralwindow {
step := size / 2
minx, miny := 0, 0
maxy := len(integral)-1
maxx := len(integral[0])-1
if y > (step+1) {
miny = y - step - 1
}
if x > (step+1) {
minx = x - step - 1
}
if maxy > (y + step) {
maxy = y + step
}
if maxx > (x + step) {
maxx = x + step
}
return integralwindow { integral[miny][minx], integral[miny][maxx], integral[maxy][minx], integral[maxy][maxx], maxx-minx, maxy-miny}
}
func integralmean(integral [][]uint64, x int, y int, size int) float64 {
i := getintegralwindow(integral, x, y, size)
total := float64(i.bottomright + i.topleft - i.topright - i.bottomleft)
sqsize := float64(i.width) * float64(i.height)
return total / sqsize
}
func integralmeanstddev(integral [][]uint64, integralsq [][]uint64, x int, y int, size int) (float64, float64) {
i := getintegralwindow(integral, x, y, size)
isq := getintegralwindow(integralsq, x, y, size)
var total, sqtotal, sqsize float64
sqsize = float64(i.width) * float64(i.height)
total = float64(i.bottomright + i.topleft - i.topright - i.bottomleft)
sqtotal = float64(isq.bottomright + isq.topleft - isq.topright - isq.bottomleft)
mean := total / sqsize
variance := (sqtotal / sqsize) - (mean * mean)
return mean, math.Sqrt(variance)
}
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