A hidden feature: dynamically resize image.

Adding width=xxx or height=xxx, or both, can dynamically resize a
gif,jpg,png. But the performance is bad. So, not recommending, but you
can use it if you insist. :)

go/weed/weed_server/volume_server_handlers.go

@@ -1,11 +1,17 @@
 package weed_server
 
 import (
+	"bytes"
 	"code.google.com/p/weed-fs/go/glog"
 	"code.google.com/p/weed-fs/go/operation"
 	"code.google.com/p/weed-fs/go/stats"
 	"code.google.com/p/weed-fs/go/storage"
 	"code.google.com/p/weed-fs/go/topology"
+	"github.com/disintegration/imaging"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
 	"mime"
 	"net/http"
 	"strconv"
@@ -118,6 +124,36 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request,
 			}
 		}
 	}
+	if ext == ".png" || ext == ".jpg" || ext == ".gif" {
+		if srcImage, _, err := image.Decode(bytes.NewReader(n.Data)); err == nil {
+			width, height := 0, 0
+			if r.FormValue("width") != "" {
+				width, _ = strconv.Atoi(r.FormValue("width"))
+			}
+			if r.FormValue("height") != "" {
+				height, _ = strconv.Atoi(r.FormValue("height"))
+			}
+			if width != 0 || height != 0 {
+				bounds := srcImage.Bounds()
+				var dstImage *image.NRGBA
+				if width == height && bounds.Dx() != bounds.Dy() {
+					dstImage = imaging.Thumbnail(srcImage, width, height, imaging.Lanczos)
+				} else {
+					dstImage = imaging.Resize(srcImage, width, height, imaging.Lanczos)
+				}
+				var buf bytes.Buffer
+				switch ext {
+				case ".png":
+					png.Encode(&buf, dstImage)
+				case ".jpg":
+					jpeg.Encode(&buf, dstImage, nil)
+				case ".gif":
+					gif.Encode(&buf, dstImage, nil)
+				}
+				n.Data = buf.Bytes()
+			}
+		}
+	}
 	w.Header().Set("Content-Length", strconv.Itoa(len(n.Data)))
 	if isGetMethod {
 		if _, e = w.Write(n.Data); e != nil {