test_kc.go

package main

import (
	"fmt"
	"image"
	"image/png"
	"math"
	"os"
	"time"

	"github.com/terrascope/scimage"
	"github.com/terrascope/scimage/scicolor"
)

func ComputeKc(im *image.NRGBA) (*scimage.GrayU8, error) {
	out := scimage.NewGrayU8(im.Rect, 0, 100, 255)

	for i := 0; i < im.Bounds().Dx(); i++ {
		for j := 0; j < im.Bounds().Dy(); j++ {
			c := im.NRGBAAt(i, j)
			red, blue, nir, swir1 := float64(c.R)*2e-3, float64(c.G)*2e-3, float64(c.B)*2e-3, float64(c.A)*2e-3

			evi := 2.5 * (nir - red) / (nir + 6*red - 7.5*blue + 1)
			gvmi := ((nir + 0.1) - (swir1 + 0.02)) / ((nir + 0.1) + (swir1 + 0.02))
			rmi := math.Max(0, gvmi-(0.775*evi-0.0757))
			evir := math.Max(0, math.Min(1, evi))

			kc := 0.680 * (1 - math.Exp(-14.12*math.Pow(evir, 2.482)-7.991*math.Pow(rmi, 0.890)))

			out.SetGrayU8(i, j, scicolor.GrayU8{Y: uint8(kc * 100)})
		}
	}

	return out, nil
}

func main() {

	fmt.Println("Hello")

	start := time.Now()
	f, err := os.Open("./refl_DEA_+13_-35_201702_l0.png")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	defer f.Close()

	im, err := png.Decode(f)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	fmt.Printf("Openning file took %s\n", time.Since(start))

	start = time.Now()
	kc, _ := ComputeKc(im.(*image.NRGBA))
	fmt.Printf("Computing Kc took %s\n", time.Since(start))

	start = time.Now()
	out, err := os.Create("./kc_DEA_+13_-35_201702_l0.png")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	err = png.Encode(out, kc)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	fmt.Printf("Saving file took %s\n", time.Since(start))

}