Androidのscreenshotの上部のnotificationエリアと下部のボタンエリアを削除したPNGを作る

main.go

package main

import (
	"fmt"
	"image"
	"image/png"
	_ "image/png"
	"os"
)

func main() {

	for _, name := range os.Args[1:] {
		f, err := os.Open(name)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			continue
		}
		defer f.Close()

		m, _, err := image.Decode(f)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			continue
		}
		fmt.Printf("%v\n", name)

		// copy image
		w := m.Bounds().Max.X - m.Bounds().Min.X
		h := m.Bounds().Max.Y - m.Bounds().Min.Y
		subImage := image.NewRGBA(image.Rectangle{image.Point{0, 0}, image.Point{w, h}})
		for y := 0; y < h; y++ {
			for x := 0; x < w; x++ {
				subImage.Set(x, y, m.At(x+m.Bounds().Min.X, y+m.Bounds().Min.Y))
			}
		}

		var trimTop int
		for y := 0; y < h; y++ {
			isBlack := isBlackLine(subImage, y)
			if !isBlack {
				trimTop = y
				break
			}
		}
		var trimBottom int
		for y := h - 1; y >= 0; y-- {
			isBlack := isBlackLine(subImage, y)
			if !isBlack {
				trimBottom = y
				break
			}
		}

		if trimTop == 0 && trimBottom == h-1 || trimBottom == 0 {
			fmt.Printf("skip\n")
			continue
		}

		fmt.Printf("trimTop=%v tripBottom=%v\n", trimTop, trimBottom)

		trimmedImage := subImage.SubImage(image.Rectangle{image.Point{0, trimTop}, image.Point{w, trimBottom + 1}})

		fmt.Printf("sub=%v\n", trimmedImage.Bounds())

		fout, err := os.OpenFile(name+".trimmed.png", os.O_WRONLY|os.O_CREATE, 0666)
		if err != nil {
			panic(err)
		}
		defer fout.Close()
		err = png.Encode(fout, trimmedImage)
		if err != nil {
			panic(err)
		}

	}
}

// 横一列にblackが50%以上入っている場合true
func isBlackLine(m image.Image, y int) bool {
	nblack := 0
	for x := m.Bounds().Min.X; x < m.Bounds().Max.X; x++ {
		r, g, b, _ := m.At(x, y).RGBA()
		if r == 0 && g == 0 && b == 0 {
			nblack++
		}
	}
	if nblack >= (m.Bounds().Max.X-m.Bounds().Min.X)/2 {
		return true
	} else {
		return false
	}

}