2017-10-18 14:49
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I need a little hint. I'm creating thumbnails of images in Go and would like to pass them to jpegoptim for crushing.

jpegoptim has the --stdin and --stdout flags, which I would like to use. Now, I don't want to save the generated image to disk first, but convert my *image.RGBA to something that implements io.Reader, so I can pass it to exec.Cmd.Stdin

I'm a little lost on how I could achieve this, would be great if someone can point me in the right direction.


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我需要一些提示。 我正在Go中创建图像的缩略图,并希望将其传递给jpegoptim进行压缩。

jpegoptim具有--stdin和--stdout标志,我想使用它们。 现在,我不想首先将生成的图像保存到磁盘,而是将我的* image.RGBA转换为实现io.Reader的东西,因此可以将其传递给exec.Cmd.Stdin



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  • dsns47611 2017-10-19 13:31

    In this case, you don't need to implement your own io.Reader. Use io.Pipe and jpeg.Encode, e.g.

    func main() {
        //Prepare image ...
        img := ...
        //Prepare output (file etc.) ...
        outFile := ...
        //Use pipe to connect JPEG encoder output to cmd's STDIN
        pr, pw := io.Pipe()
        //Exec jpegoptim in goroutine
        done := make(chan bool, 1)
        go func() {
            //execute command
            cmdErr := bytes.Buffer{}
            cmd := exec.Command("jpegoptim", "--stdin", "--verbose")
            cmd.Stdin = pr       //image input from PIPE
            cmd.Stderr = &cmdErr //message
            cmd.Stdout = outFile //optimize image output
            if err := cmd.Run(); err != nil {
                // handle error
            fmt.Printf("Result: %s
    ", cmdErr.String())
        //ENCODE image to JPEG then write to PIPE
        o := jpeg.Options{Quality: 90}
        jpeg.Encode(pw, img, &o)
        //When done, close the PIPE
        if err := pw.Close(); err != nil {
            // handle error
        //Wait for jpegoptim
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