AWS Lambda GO 和图像响应损坏

Question

currently I'm trying to proxy images through a go lambda function from S3 backend. basically i retrieve the image as []byte from S3 and try to pass it to the browser as image/png

imgData := repository.GetBinary(cType, cId, uuid)

    b64img := base64.StdEncoding.EncodeToString(imgData)

    return events.APIGatewayProxyResponse{
        StatusCode: http.StatusOK,
        Body:       b64img,
        IsBase64Encoded: true,
        Headers: map[string]string{
            "Content-Type":              "image/png",
        },
    }, nil

I tried it as base64 encoded as well as not. The image won't be rendered.

When i do it without lambda as go server it works fine.

    lib.Init()
    // disable validation here
    lib.App.ValidateHeader = false
    b := repository.GetBinary(cType, cId, uuid)

    w.Header().Set("Content-Type", "text/plain")

    img := bytes.NewReader(b)

    w.Header().Set("Content-Type", "image/png")
    w.WriteHeader(http.StatusOK)
    io.Copy(w,img)

I don't know what I'm doing wrong...

Answer 1

I got it working after adding the Content-Length header:

    buf := new(bytes.Buffer)
    if err := png.Encode(buf, image); err != nil {
        return errorResponse(err)
    }

    b64img := base64.StdEncoding.EncodeToString(buf.Bytes())

    return &events.APIGatewayProxyResponse{
        StatusCode: http.StatusOK,
        Headers: map[string]string{
            "Content-Type":   "image/png",
            "Content-Length": fmt.Sprintf("%d", len(b64img)),
        },
        Body:            b64img,
        IsBase64Encoded: true,
    }, nil