Open jamesbikes opened 7 years ago
The gist is disabled in China. Can you paste the gist code?
And any PR are welcome.
Thanks for your feedback!
Sure! Sorry, a bit tight on time right now. May be able to make a PR later if you don't get to it first.
package main
import (
"image"
"image/color"
"image/draw"
"image/jpeg"
_ "image/png"
"log"
"os"
_ "github.com/chai2010/webp"
)
func main() {
if len(os.Args) != 3 {
log.Fatal("pass file")
}
in, _ := os.Open(os.Args[1])
defer in.Close()
img, _, _ := image.Decode(in)
r := image.NewRGBA(img.Bounds())
draw.Draw(r, img.Bounds(), &image.Uniform{color.White}, image.ZP, draw.Src)
draw.Draw(r, img.Bounds(), img, image.ZP, draw.Over)
out, _ := os.Create(os.Args[2])
defer out.Close()
jpeg.Encode(out, r, nil)
}
Ran into this problem too. Decoded webp with alpha channel has damaged edges and colors. @chai2010 please can you look into?
A simple test to load webp and encode it to png fails:
import (
"bytes"
_ "embed"
_ "github.com/chai2010/webp"
"image"
"image/png"
"os"
)
//go:embed sticker.webp
var data []byte
func main() {
img, _, err := image.Decode(bytes.NewReader(data))
if err != nil {
panic(err)
}
f, err := os.Create("out.png")
if err != nil {
panic(err)
}
defer f.Close()
if err := png.Encode(f, img); err != nil {
panic(err)
}
}
Expected result is:
Actual:
The webp libraries return non-premultiplied alpha values. This library wraps those values in RGBA structs which represent premultiplied values.
Everywhere
RGBA{}
is created with data returned by the webp decoder, it should beNRGBA{}
.e.g. this fixes one of them: https://github.com/chai2010/webp/compare/master...jamesshoebox:nrgba?expand=1
Here's a (very) simple program that illustrates the problem. If you pass in a webp with alpha, you'll see that it doesn't blend correctly with the white background. https://gist.github.com/jamesshoebox/30ca5beada606842f98328481bf17f8d