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image.go
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image.go
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package lib
import (
"bytes"
"encoding/base64"
"fmt"
"html/template"
"image"
"image/gif"
"image/jpeg"
"image/png"
"io/ioutil"
"net/http"
"os"
"path"
"regexp"
"strconv"
log "github.com/inconshreveable/log15"
. "github.com/netsec-ethz/scion-apps/webapp/util"
)
var regexImageFiles = `([^\s]+(\.(?i)(jp?g|png|gif))$)`
var imgTemplate = `<!doctype html><html lang="en"><head></head><body>
<a href="{{.ImgUrl}}" target="_blank"><img src="data:image/jpg;base64,{{.JpegB64}}">
</a></body>`
// Handles writing jpeg image to http response writer by content-type.
func writeJpegContentType(w http.ResponseWriter, img *image.Image) {
buf := new(bytes.Buffer)
err := jpeg.Encode(buf, *img, nil)
CheckError(err)
w.Header().Set("Content-Type", "image/jpeg")
w.Header().Set("Content-Length", strconv.Itoa(len(buf.Bytes())))
_, werr := w.Write(buf.Bytes())
CheckError(werr)
}
// Handles writing jpeg image to http response writer by image template.
func writeJpegTemplate(w http.ResponseWriter, img *image.Image, url string) {
buf := new(bytes.Buffer)
err := jpeg.Encode(buf, *img, nil)
CheckError(err)
str := base64.StdEncoding.EncodeToString(buf.Bytes())
tmpl, err := template.New("image").Parse(imgTemplate)
if CheckError(err) {
return
}
data := map[string]interface{}{"JpegB64": str, "ImgUrl": url}
err = tmpl.Execute(w, data)
CheckError(err)
}
// Helper method to find most recently modified regex extension filename in dir.
func findNewestFileExt(dir, extRegEx string) (imgFilename string, imgTimestamp int64) {
files, _ := ioutil.ReadDir(dir)
for _, f := range files {
fi, err := os.Stat(path.Join(dir, f.Name()))
CheckError(err)
matched, err := regexp.MatchString(extRegEx, f.Name())
CheckError(err)
if matched {
modTime := fi.ModTime().Unix()
if modTime > imgTimestamp {
imgTimestamp = modTime
imgFilename = f.Name()
}
}
}
return
}
// FindImageInfoHandler locating most recent image and writing text info data about it.
func FindImageInfoHandler(w http.ResponseWriter, r *http.Request) {
filesDir := "."
imgFilename, _ := findNewestFileExt(filesDir, regexImageFiles)
if imgFilename == "" {
return
}
fileText := imgFilename
fmt.Fprintf(w, fileText)
}
// FindImageHandler locating most recent image formatting it for graphic display in response.
func FindImageHandler(w http.ResponseWriter, r *http.Request, browserAddr string, port int) {
filesDir := "."
imgFilename, _ := findNewestFileExt(filesDir, regexImageFiles)
if imgFilename == "" {
fmt.Fprint(w, "Error: Unable to find image file locally.")
return
}
log.Info("Found image file:", "imgFilename", imgFilename)
imgFile, err := os.Open(path.Join(filesDir, imgFilename))
CheckError(err)
defer imgFile.Close()
_, imageType, err := image.Decode(imgFile)
CheckError(err)
log.Info("Found image type: ", "imageType", imageType)
// reset file pointer to beginning
imgFile.Seek(0, 0)
var rawImage image.Image
switch imageType {
case "gif":
rawImage, err = gif.Decode(imgFile)
case "png":
rawImage, err = png.Decode(imgFile)
case "jpeg":
rawImage, err = jpeg.Decode(imgFile)
default:
panic("Unhandled image type!")
}
CheckError(err)
url := fmt.Sprintf("http://%s:%d/%s/%s", browserAddr, port, "images", imgFilename)
writeJpegTemplate(w, &rawImage, url)
}