blob: dfff8b6aa8fcc39851096ea8a7ece553b793cda9 [file] [log] [blame]
// Copyright 2020 The Wuffs 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
//
// https://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
// draw-with-mask.go draws one image using a second image as an alpha mask
// (scaled to the size fo the first image). The resultant image is PNG-encoded
// to stdout.
//
// The result isn't necessarily beautiful, but it is an easy way to generate
// test images containing an alpha channel.
//
// Usage: go run draw-with-mask.go color.png alpha.png > foo.png
import (
"bufio"
"errors"
"image"
"image/png"
"os"
"golang.org/x/image/draw"
_ "image/gif"
_ "image/jpeg"
)
func main() {
if err := main1(); err != nil {
os.Stderr.WriteString(err.Error() + "\n")
os.Exit(1)
}
}
func main1() error {
if len(os.Args) != 3 {
return errors.New(`bad arguments: usage: "go draw-with-mask.go color.png alpha.png"`)
}
color, err := decode(os.Args[1])
if err != nil {
return err
}
alpha, err := decode(os.Args[2])
if err != nil {
return err
}
b := color.Bounds()
mask := makeMask(b, alpha)
dst := image.NewRGBA(b)
draw.DrawMask(dst, b, color, b.Min, mask, mask.Bounds().Min, draw.Src)
w := bufio.NewWriter(os.Stdout)
defer w.Flush()
return png.Encode(w, dst)
}
func decode(filename string) (image.Image, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close()
m, _, err := image.Decode(f)
return m, err
}
func makeMask(bounds image.Rectangle, src image.Image) *image.Alpha {
dst := image.NewGray(bounds)
draw.CatmullRom.Scale(dst, dst.Bounds(), src, src.Bounds(), draw.Src, nil)
return &image.Alpha{
Pix: dst.Pix,
Stride: dst.Stride,
Rect: dst.Rect,
}
}