diff --git a/ebitenutil/internal/assets/png2rgba.go b/ebitenutil/internal/assets/png2rgba.go
deleted file mode 100644
index 0e588ad66..000000000
--- a/ebitenutil/internal/assets/png2rgba.go
+++ /dev/null
@@ -1,90 +0,0 @@
-// Copyright 2018 The Ebiten Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build ignore
-// +build ignore
-
-package main
-
-import (
-	"compress/gzip"
-	"flag"
-	"image/png"
-	"io"
-	"os"
-)
-
-var (
-	inputFilename  = flag.String("input", "", "input file name")
-	outputFilename = flag.String("output", "", "output file name")
-)
-
-func run() error {
-	var in io.Reader
-	if *inputFilename != "" {
-		f, err := os.Open(*inputFilename)
-		if err != nil {
-			return err
-		}
-		defer f.Close()
-		in = f
-	} else {
-		in = os.Stdin
-	}
-
-	var out io.Writer
-	if *outputFilename != "" {
-		f, err := os.Create(*outputFilename)
-		if err != nil {
-			return err
-		}
-		defer f.Close()
-		out = f
-	} else {
-		out = os.Stdout
-	}
-
-	img, err := png.Decode(in)
-	if err != nil {
-		return err
-	}
-
-	b := img.Bounds()
-	w, h := b.Dx(), b.Dy()
-	rgba := make([]byte, w*h*4)
-	for j := 0; j < h; j++ {
-		for i := 0; i < w; i++ {
-			r, g, b, a := img.At(i, j).RGBA()
-			rgba[4*(w*j+i)] = byte(r >> 8)
-			rgba[4*(w*j+i)+1] = byte(g >> 8)
-			rgba[4*(w*j+i)+2] = byte(b >> 8)
-			rgba[4*(w*j+i)+3] = byte(a >> 8)
-		}
-	}
-
-	cw := gzip.NewWriter(out)
-	defer cw.Close()
-
-	if _, err := cw.Write(rgba); err != nil {
-		return err
-	}
-	return nil
-}
-
-func main() {
-	flag.Parse()
-	if err := run(); err != nil {
-		panic(err)
-	}
-}