From 6816585d613a6df4ae10eadcb8e8af9b81666d03 Mon Sep 17 00:00:00 2001
From: CrispyBaguette <alexandre.bruyant@gmail.com>
Date: Sat, 11 Dec 2021 17:54:15 +0100
Subject: [PATCH] Handle images as Blobs

---
 client/src/App.tsx | 10 ++++++----
 src/wasm.go        | 17 ++++++++++++-----
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/client/src/App.tsx b/client/src/App.tsx
index 37eadfb..2c1d49c 100644
--- a/client/src/App.tsx
+++ b/client/src/App.tsx
@@ -10,7 +10,6 @@ function App() {
       return;
     }
     const workerProxy: any = await wasmWorker("main.wasm");
-
     setImageSrc("");
 
     // Check if a file was selected
@@ -23,9 +22,12 @@ function App() {
     reader.onloadend = async (evt) => {
       if (evt.target!.readyState === FileReader.DONE) {
         const imageData = new Uint8Array(evt.target!.result as ArrayBuffer);
-        const ditheredImage = await workerProxy.DitherNord(imageData);
-        const outputValue = `data:image/png;base64,${ditheredImage}`;
-        setImageSrc(outputValue);
+        const ditheredImageArray = await workerProxy.DitherNord(imageData);
+        const imageBlob = new Blob([ditheredImageArray.buffer], {
+          type: "image/png",
+        });
+        const url = URL.createObjectURL(imageBlob);
+        setImageSrc(url);
       }
     };
   };
diff --git a/src/wasm.go b/src/wasm.go
index 67524c8..0df7edf 100644
--- a/src/wasm.go
+++ b/src/wasm.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	b64 "encoding/base64"
 	"encoding/hex"
 	"image"
 	"image/color"
@@ -69,7 +68,7 @@ func decodeImage(imageData []byte) (image.Image, error) {
 }
 
 // DittherNord returns a Promise that takes a UintArray containing a Jpeg or png image,
-// and resolves to a string containing a base64 encoded png image.
+// and resolves to a UintArray containing the dithered image.
 func DitherNord() js.Func {
 	return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 		imageBytes := make([]byte, args[0].Length())
@@ -96,12 +95,20 @@ func DitherNord() js.Func {
 				log.Printf("Image dithered in %v\n", t2.Sub(t1))
 
 				// Encode as PNG
+				log.Println("Encoding image...")
+				t1 = time.Now()
 				buf := new(bytes.Buffer)
 				png.Encode(buf, ditheredImage)
+				t2 = time.Now()
+				log.Printf("Image encoded in %v\n", t2.Sub(t1))
 
-				// Encode as img src b64 string and resolve
-				encodedImage := b64.StdEncoding.EncodeToString(buf.Bytes())
-				resolve.Invoke(js.ValueOf(encodedImage))
+				log.Println("Copying image to JS...")
+				t1 = time.Now()
+				encodedImage := js.Global().Get("Uint8ClampedArray").New(len(buf.Bytes()))
+				js.CopyBytesToJS(encodedImage, buf.Bytes())
+				t2 = time.Now()
+				log.Printf("Image copied in %v\n", t2.Sub(t1))
+				resolve.Invoke(encodedImage)
 			}()
 
 			return nil