How to Efficiently Encode a Resized image.Image to a []byte in Go?

Decoding and Encoding Images Using Go

In Go, converting an image from an image.Image type to a byte slice ([]byte) is essential for storing and transmitting image data. This article presents a common issue encountered during this conversion and provides a solution.

The code snippet provided attempts to download an image from a bucket, decode it into an image.Image, resize it, and then convert the resized image back to a byte slice for uploading to S3. However, the highlighted section of the code is where the issue lies.

// reset format the image.Image to data []byte here
var send_S3 []byte
var byteWriter = bufio.NewWriter(send_S3)
err = jpeg.Encode(byteWriter, new_image, nil)

The issue is that a bufio.Writer is used for caching data before writing it to another writer, but in this case, we need to write directly to a memory buffer. To resolve this, we use a bytes.Buffer instead, which writes to memory.

buf := new(bytes.Buffer)
err := jpeg.Encode(buf, new_image, nil)
send_s3 := buf.Bytes()

By using a bytes.Buffer, the resized image is written directly to memory, creating the byte slice that is suitable for uploading to S3. This allows the code to successfully encode and upload the resized image to the desired bucket.

The above is the detailed content of How to Efficiently Encode a Resized image.Image to a []byte in Go?. For more information, please follow other related articles on the PHP Chinese website!