get & save picture size, width and height

picture.go

package main

import (
	"database/sql"
	"flag"
	"fmt"
	_ "github.com/go-sql-driver/mysql"
	"github.com/go-yaml/yaml"
	"image"
	_ "image/gif"
	_ "image/jpeg"
	_ "image/png"
	"io/ioutil"
	"os"
)

var db *sql.DB
var config *Configuration
var dir string

type Configuration struct {
	Dir string `yaml:"dir"`
	DSN string `yaml:"dsn"`
}

type Picture struct {
	Id       string
	Hash     string
	MimeType string
	Width    int
	Height   int
	Size     int64
}

func init() {
	config = &Configuration{}
	var configFile string
	flag.StringVar(&configFile, "c", "settings.yaml", "config file name")
	flag.Parse()
	if ctx, err := ioutil.ReadFile(configFile); err != nil {
		panic(err)
	} else {
		if err := yaml.Unmarshal(ctx, &config); err != nil {
			panic(err)
		}
	}
}

func main() {
	var err error
	db, err = sql.Open("mysql", config.DSN)
	if err != nil {
		panic(err)
	}
	stmt, err := db.Prepare("SELECT picture_id, hash, mime_type FROM picture WHERE size=0 OR width=0 OR height=0")
	if err != nil {
		panic(err)
	}
	rows, err := stmt.Query()
	if err != nil {
		panic(err)
	}
	for rows.Next() {
		picture := Picture{}
		rows.Scan(&picture.Id, &picture.Hash, &picture.MimeType)
		err := picture.Process()
		if err != nil {
			fmt.Println(err)
		} else {
			if _, err := db.Exec("UPDATE picture SET size=?, width=?, height=? WHERE picture_id=?", picture.Size, picture.Width, picture.Height, picture.Id); err != nil {
				fmt.Println(err)
			}
		}
	}
}

func (picture *Picture) Process() error {
	path := config.Dir + fmt.Sprintf("/%s/%s/%s/%s/%s", picture.Hash[0:2], picture.Hash[2:4], picture.Hash[4:7], picture.Hash[7:10], picture.Hash[10:])
	switch picture.MimeType {
	case "image/jpeg":
		path += ".jpg"
	case "image/png":
		path += ".png"
	case "image/gif":
		path += ".gif"
	}
	file, err := os.Open(path)
	if err != nil {
		return err
	}
	fileInfo, err := file.Stat()
	if err != nil {
		return err
	}
	picture.Size = fileInfo.Size()
	imageConfig, _, err := image.DecodeConfig(file)
	if err != nil {
		return err
	}
	picture.Height = imageConfig.Height
	picture.Width = imageConfig.Width
	return nil
}