调整图像大小

Question

I am using the Go resize package here: https://github.com/nfnt/resize

1. I am pulling an Image from S3, as such:

   image_data, err := mybucket.Get(key)
   // this gives me data []byte
   

2. After that, I need to resize the image:

   new_image := resize.Resize(160, 0, original_image, resize.Lanczos3)
   // problem is that the original_image has to be of type image.Image
   

3. Upload the image to my S3 bucket

   err : = mybucket.Put('newpath', new_image, 'image/jpg', 'aclstring')
   // problem is that new image needs to be data []byte
   

How do I transform a data []byte to ---> image.Image and back to ----> data []byte?

Answer 1

Read http://golang.org/pkg/image

// you need the image package, and a format package for encoding/decoding
import (
    "bytes"
    "image"
    "image/jpeg"

    "github.com/nfnt/resize"

    // if you don't need to use jpeg.Encode, import like so:
    // _ "image/jpeg"
)

// Decoding gives you an Image.
// If you have an io.Reader already, you can give that to Decode 
// without reading it into a []byte.
image, _, err := image.Decode(bytes.NewReader(data))
// check err

newImage := resize.Resize(160, 0, original_image, resize.Lanczos3)

// Encode uses a Writer, use a Buffer if you need the raw []byte
err = jpeg.Encode(someWriter, newImage, nil)
// check err