perf: regenerate the url only when the orientation was reset

Closes #63

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## next
+
+- Regenerate the initial url only when the orientation was reset for better performance (#63).
+
 ## 1.0.3 (Dec 18, 2018)
 
 - Convert `TypedArray` to `Array` manually instead of using Babel helpers for better browser compatibility (#60).

src/index.js

@@ -75,15 +75,24 @@ export default class Compressor {
       this.reader = reader;
       reader.onload = ({ target }) => {
         const { result } = target;
+        const data = {
+          url: result,
+        };
 
-        this.load(checkOrientation ? {
+        if (checkOrientation) {
           // Should reset the orientation value to its default value first
           // as some iOS browsers will render image with its orientation
-          ...parseOrientation(resetAndGetOrientation(result)),
-          url: arrayBufferToDataURL(result, mimeType),
-        } : {
-          url: result,
-        });
+          const orientation = resetAndGetOrientation(result);
+
+          Object.assign(data, parseOrientation(orientation));
+
+          // Regenerate the url only when the orientation was reset for better performance.
+          if (orientation > 1) {
+            data.url = arrayBufferToDataURL(result, mimeType);
+          }
+        }
+
+        this.load(data);
       };
       reader.onabort = () => {
         this.fail(new Error('Aborted to read the image with FileReader.'));

src/utilities.js

@@ -75,6 +75,7 @@ export function arrayBufferToDataURL(arrayBuffer, mimeType) {
   let uint8 = new Uint8Array(arrayBuffer);
 
   while (uint8.length > 0) {
+    // XXX: Babel's `toConsumableArray` helper will throw error in IE or Safari 9
     // eslint-disable-next-line prefer-spread
     chunks.push(fromCharCode.apply(null, toArray(uint8.subarray(0, chunkSize))));
     uint8 = uint8.subarray(chunkSize);