[adamchalmers#2] Larger images need to be resampled

main.js

@@ -30,18 +30,17 @@ $(function() {
 i = 0; 
 $("#start").on("click", function() {
     // Load the target and approximation images.
-    var targetPrefix = "/remote/img?url=";
-    var approxPrefix = "/approx/img?url=";
-    var imgUrl = $("#imgUrl").val();
+    const targetPrefix = "/remote/img?url=";
+    const approxPrefix = "/approx/img?url=";
+    const imgUrl = $("#imgUrl").val();
     $("#target-image").attr("src", targetPrefix + imgUrl).css("height", "auto").css("width", "auto");
     $("#approx-image").attr("src", approxPrefix + imgUrl + "&" + i++).css("height", "auto").css("width", "auto");
     console.log("Rendering", imgUrl);
-    var startTime = (new Date()).getTime();
+    const startTime = (new Date()).getTime();
 
 
-    // Once the target has loaded, we can check it's within the size limits.
+    // Once the target has loaded, we can display it
     $("#target-image").on("load", function() {
-        // If it is, show the images and stats.
         $("#error").text("");
         $(this).show();
         $("#approx-image").show();
@@ -55,5 +54,4 @@ $("#start").on("click", function() {
             console.log("Took " + Math.round(((new Date()).getTime()-startTime)/1000) + " seconds.");
         });
     });
-
 });

server.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"github.com/nfnt/resize"
 	"image"
 	_ "image/gif"
 	_ "image/jpeg"
@@ -61,13 +62,22 @@ func urlParam(r *http.Request) (string, error) {
 // This allows us to get around CORS issues.
 func remoteHandler(w http.ResponseWriter, r *http.Request) {
 	img, err := getImg(r)
+
 	if err != nil {
 		log.Println(err)
 		w.Write([]byte(err.Error()))
 		return
 	}
+
 	defer img.Close()
-	io.Copy(w, img)
+
+	_target, _, err := image.Decode(img)
+
+	ci := make(chan image.Image)
+	go preprocessImage(_target, ci)
+	preprocessedImage := <-ci
+
+	png.Encode(w, preprocessedImage)
 }
 
 // Serves the image generated by approximate() on the URL in the request.
@@ -98,12 +108,12 @@ func approxHandler(w http.ResponseWriter, r *http.Request) {
 		fmt.Println(err)
 		return
 	}
-	if dx, dy := _target.Bounds().Dx(), _target.Bounds().Dy(); dx > MAXSIZE || dy > MAXSIZE {
-		msg := fmt.Sprintf("Image of size %v.%v is too large (max size is %v)", dx, dy, MAXSIZE)
-		io.Copy(w, strings.NewReader(msg))
-	}
 
-	target := toRGBA(_target)
+	ci := make(chan image.Image)
+	go preprocessImage(_target, ci)
+	preprocessedTarget := <-ci
+
+	target := toRGBA(preprocessedTarget)
 
 	approximation, score := approximate(
 		target,
@@ -120,6 +130,21 @@ func approxHandler(w http.ResponseWriter, r *http.Request) {
 	}}
 }
 
+func preprocessImage(image image.Image, cr chan image.Image) {
+	if dx, dy := image.Bounds().Dx(), image.Bounds().Dy(); dx > MAXSIZE || dy > MAXSIZE {
+		// Resample the image down to MAXSIZE
+		msg := fmt.Sprintf("Image of size %v.%v is too large (max size is %v). Downsampling.", dx, dy, MAXSIZE)
+		log.Println(msg)
+
+		cr <- resize.Thumbnail(MAXSIZE,
+			MAXSIZE,
+			image,
+			resize.NearestNeighbor)
+	} else {
+		cr <- image
+	}
+}
+
 // Serve a static file.
 func fileHandler(w http.ResponseWriter, r *http.Request) {
 	http.SetCookie(w, &http.Cookie{