image_server.go

package main

import (
    "fmt"
    "net/http"
    "os"
    "strings"
    "strconv"
    "github.com/Terry-Mao/paint"
    "github.com/Terry-Mao/paint/wand"
)

func main() {
    http.HandleFunc("/", handler)

    fmt.Printf("Server ready\n")
    http.ListenAndServe(":8080", nil)
}

func handler(w http.ResponseWriter, r *http.Request) {
    image_path := r.URL.Path[1:]
    size_param := r.URL.Query().Get("size")
    cached_img_name := createImageFileName(image_path, size_param)

    exists, _ := fileExists(cached_img_name)
    fmt.Printf("%v %v \n", cached_img_name, exists)

    if !exists {
      if(size_param != ""){
        resizeImage(w, r, image_path, size_param)
      } else {
        http.ServeFile(w, r, cached_img_name)
      }
    } else {
      // We know it doesnt exists, but this handles 404's well
      http.ServeFile(w, r, cached_img_name)
    }
}

func resizeImage(w http.ResponseWriter,
                 r *http.Request,
                 fileName, size_param string){

    width, height := parseWidthHeight(size_param)
    fmt.Printf("resizing to %d, %d \n", width, height)

    wand.Genesis()
    defer wand.Terminus()
    magick := wand.NewMagickWand()
    defer magick.Destroy()

    err := magick.ReadImage(fileName);
    check(w, err)

    err = paint.Thumbnail(magick, uint(width), uint(height))
    check(w, err)

    cached_img_name := createImageFileName(fileName, size_param)

    err = magick.WriteImage(cached_img_name)
    check(w, err)

    http.ServeFile(w, r, cached_img_name)
}

// exists returns whether the given file or directory exists or not
func fileExists(path string) (bool, error) {
    _, err := os.Stat(path)
    if err == nil { return true, nil }
    if os.IsNotExist(err) { return false, nil }
    return false, err
}

func parseWidthHeight(s string) (int, int) {
    width_height := strings.Split(s, "x")
    width,  _ := strconv.Atoi(width_height[0])
    height, _ := strconv.Atoi(width_height[1])
    return width, height
}

func createImageFileName(imageName, size string) string {
    if size == "" {
      return imageName
    }
    name_split := strings.Split(imageName, ".")
    return name_split[0] + size + "." + name_split[1]
}

func check(w http.ResponseWriter, err error) {
    if err != nil {
      http.Error(w, err.Error(), 404)
      panic(err)
    }
}