encoding.go

package main

import (
	"bytes"
	"encoding/base64"
	"image"
	"image/jpeg"
	"image/png"
)

type ImageEncoding string

var (
	PNG  ImageEncoding = "PNG"
	JPEG ImageEncoding = "JPEG"

	imageEncoders = map[ImageEncoding]ImageStringEncoder{
		PNG:  &PngImageStringEncoder{},
		JPEG: &JpegImageStringEncoder{},
	}
)

type ImageStringEncoder interface {
	encodeImage(i image.Image) (string, error)
}

type PngImageStringEncoder struct{}

func (e *PngImageStringEncoder) encodeImage(image image.Image) (string, error) {
	var buf bytes.Buffer
	err := png.Encode(&buf, image)
	if err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(buf.Bytes()), nil
}

type JpegImageStringEncoder struct{}

func (e *JpegImageStringEncoder) encodeImage(image image.Image) (string, error) {
	var buf bytes.Buffer
	err := jpeg.Encode(&buf, image, &jpeg.Options{Quality: 100})
	if err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(buf.Bytes()), nil
}