diff --git a/examples/keyboard/keyboard/gen.go b/examples/keyboard/keyboard/gen.go
index 08332a9c5..69876ee19 100644
--- a/examples/keyboard/keyboard/gen.go
+++ b/examples/keyboard/keyboard/gen.go
@@ -17,6 +17,7 @@
 package main
 
 import (
+	"bytes"
 	"errors"
 	"image"
 	"image/color"
@@ -24,11 +25,11 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"text/template"
 
 	"github.com/golang/freetype/truetype"
+	"github.com/hajimehoshi/file2byteslice"
 	"golang.org/x/image/font"
 
 	"github.com/hajimehoshi/ebiten"
@@ -237,26 +238,20 @@ func outputKeyboardImage() (map[ebiten.Key]image.Rectangle, error) {
 		y += height
 	}
 
-	f, err := ioutil.TempFile("", "ebiten")
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		return nil, err
+	}
+
+	out, err := os.Create("../../resources/images/keyboard/keyboard.go")
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer out.Close()
 
-	if err := png.Encode(f, img); err != nil {
+	if err := file2byteslice.Write(out, &buf, false, "", "keyboard", "Keyboard_png"); err != nil {
 		return nil, err
 	}
-
-	args := []string{
-		"-package=keyboard",
-		"-input=" + f.Name(),
-		"-output=../../resources/images/keyboard/keyboard.go",
-		"-var=Keyboard_png",
-	}
-	if err := exec.Command("file2byteslice", args...).Run(); err != nil {
-		return nil, err
-	}
-
 	return keyMap, nil
 }
 
diff --git a/examples/resources/generate.go b/examples/resources/generate.go
index 90284dba3..12fa28b54 100644
--- a/examples/resources/generate.go
+++ b/examples/resources/generate.go
@@ -44,3 +44,11 @@
 //go:generate gofmt -s -w .
 
 package resources
+
+import (
+	// Dummy imports for go.mod for some Go files with 'ignore' tags. For example, `go mod tidy` does not
+	// recognize Go files with 'ignore' build tag.
+	//
+	// Note that this affects only importing this package, but not 'file2byteslice' commands in //go:generate.
+	_ "github.com/hajimehoshi/file2byteslice"
+)
diff --git a/examples/resources/images/keyboard/keyboard.go b/examples/resources/images/keyboard/keyboard.go
index 43966cac2..9edc1734c 100644
--- a/examples/resources/images/keyboard/keyboard.go
+++ b/examples/resources/images/keyboard/keyboard.go
@@ -1,5 +1,4 @@
 // Code generated by file2byteslice. DO NOT EDIT.
-// (gofmt is fine after generating)
 
 package keyboard
 
diff --git a/go.mod b/go.mod
index 8abb35abe..fe013cccc 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,7 @@ require (
 	github.com/gofrs/flock v0.7.1
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/hajimehoshi/bitmapfont v1.2.0
+	github.com/hajimehoshi/file2byteslice v0.0.0-20200812174855-0e5e8a80490e
 	github.com/hajimehoshi/go-mp3 v0.3.0
 	github.com/hajimehoshi/oto v0.6.3
 	github.com/jakecoffman/cp v1.0.0
diff --git a/go.sum b/go.sum
index b3e639dfe..3b06d1732 100644
--- a/go.sum
+++ b/go.sum
@@ -7,6 +7,8 @@ github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF0
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
 github.com/hajimehoshi/bitmapfont v1.2.0 h1:hw6OjRGdgmHUe56BPju/KU/QD/KLOiTQ+6t+TJpfSfU=
 github.com/hajimehoshi/bitmapfont v1.2.0/go.mod h1:h9QrPk6Ktb2neObTlAbma6Ini1xgMjbJ3w7ysmD7IOU=
+github.com/hajimehoshi/file2byteslice v0.0.0-20200812174855-0e5e8a80490e h1:4IP7CPObI35+mQShFOYg2JMHDJKciLTW5599inhFfkA=
+github.com/hajimehoshi/file2byteslice v0.0.0-20200812174855-0e5e8a80490e/go.mod h1:CqqAHp7Dk/AqQiwuhV1yT2334qbA/tFWQW0MD2dGqUE=
 github.com/hajimehoshi/go-mp3 v0.3.0 h1:fTM5DXjp/DL2G74HHAs/aBGiS9Tg7wnp+jkU38bHy4g=
 github.com/hajimehoshi/go-mp3 v0.3.0/go.mod h1:qMJj/CSDxx6CGHiZeCgbiq2DSUkbK0UbtXShQcnfyMM=
 github.com/hajimehoshi/oto v0.6.1 h1:7cJz/zRQV4aJvMSSRqzN2TImoVVMpE0BCY4nrNJaDOM=
@@ -53,6 +55,7 @@ golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLL
 golang.org/x/net v0.0.0-20200625001655-4c5254603344/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208 h1:qwRHBd0NqMbJxfbotnDhm2ByMI1Shq4Y6oRJo21SGJA=
 golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
diff --git a/internal/glfw/gen.go b/internal/glfw/gen.go
index fc90df60b..3d82973bb 100644
--- a/internal/glfw/gen.go
+++ b/internal/glfw/gen.go
@@ -24,6 +24,7 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/hajimehoshi/file2byteslice"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -106,18 +107,20 @@ func run() error {
 			return err
 		}
 
-		args = []string{
-			"-input",
-			dll,
-			"-output",
-			fmt.Sprintf("glfwdll_windows_%s.go", arch),
-			"-package",
-			"glfw",
-			"-var",
-			"glfwDLLCompressed",
-			"-compress",
+		in, err := os.Open(dll)
+		if err != nil {
+			return err
 		}
-		if err := execCommand("file2byteslice", args...); err != nil {
+		defer in.Close()
+
+		out, err := os.Create(fmt.Sprintf("glfwdll_windows_%s.go", arch))
+		if err != nil {
+			return err
+		}
+		defer out.Close()
+
+		// As the file name already specified the build environment, buildtags are not requried.
+		if err := file2byteslice.Write(out, in, true, "", "glfw", "glfwDLLCompressed"); err != nil {
 			return err
 		}