diff --git a/admin/sync/themes.go b/admin/sync/themes.go
index f3b9fb7f..a9b5366e 100644
--- a/admin/sync/themes.go
+++ b/admin/sync/themes.go
@@ -3,13 +3,17 @@ package sync
 import (
 	"errors"
 	"fmt"
+	"image"
+	"image/jpeg"
 	"math/rand"
+	"os"
 	"path"
 	"regexp"
 	"strings"
 	"unicode"
 
 	"github.com/julienschmidt/httprouter"
+	"golang.org/x/image/draw"
 	"gopkg.in/russross/blackfriday.v2"
 	"srs.epita.fr/fic-server/libfic"
 )
@@ -31,6 +35,42 @@ func GetThemes(i Importer) ([]string, error) {
 	return themes, nil
 }
 
+// resizePicture makes the given image just fill the given rectangle.
+func resizePicture(importedPath string, rect image.Rectangle) error {
+	if fl, err := os.Open(importedPath); err != nil {
+		return err
+	} else {
+		if src, _, err := image.Decode(fl); err != nil {
+			fl.Close()
+			return err
+		} else if src.Bounds().Max.X > rect.Max.X && src.Bounds().Max.Y > rect.Max.Y {
+			fl.Close()
+
+			mWidth := rect.Max.Y * src.Bounds().Max.X / src.Bounds().Max.Y
+			mHeight := rect.Max.X * src.Bounds().Max.Y / src.Bounds().Max.X
+
+			if mWidth > rect.Max.X {
+				rect.Max.X = mWidth
+			} else {
+				rect.Max.Y = mHeight
+			}
+			dst := image.NewRGBA(rect)
+			draw.CatmullRom.Scale(dst, rect, src, src.Bounds(), draw.Over, nil)
+
+			dstFile, err := os.Create(importedPath)
+			if err != nil {
+				return err
+			}
+			defer dstFile.Close()
+
+			if err = jpeg.Encode(dstFile, dst, &jpeg.Options{100}); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 // getAuthors parses the AUTHORS file.
 func getAuthors(i Importer, tname string) ([]string, error) {
 	if authors, err := getFileContent(i, path.Join(tname, "AUTHORS.txt")); err != nil {
@@ -126,6 +166,10 @@ func SyncThemes(i Importer) []string {
 			if len(btheme.Image) > 0 {
 				if _, err := i.importFile(btheme.Image,
 					func(filePath string, origin string) (interface{}, error) {
+						if err := resizePicture(filePath, image.Rect(0, 0, 500, 300)); err != nil {
+							return nil, err
+						}
+
 						btheme.Image = strings.TrimPrefix(filePath, fic.FilesDir)
 						return nil, nil
 					}); err != nil {