修复时间计算

test/index.html

@@ -82,6 +82,7 @@
         if (file) {
             const reader = new FileReader();
             reader.onload = function(e) {
+                startTime=Date.now();
                 const buffer = base64ToArrayBuffer(e.target.result.split(",")[1]);
                 const targetWidth = document.getElementById("width").value;
                 const targetHeight = document.getElementById("height").value;