Take the bigger the dimension

src/components/ImageEditor.vue

@@ -86,12 +86,14 @@ function onDrop(event: DragEvent) {
     const dx = canvas.value!.width;
     const imageData = ctx.getImageData(0, 0, canvas.value!.width, canvas.value!.height);
     canvas.value!.width += img.width;
+    canvas.value!.height = Math.max(canvas.value!.height, img.height);
     ctx.putImageData(imageData, 0, 0)
     ctx.drawImage(img, dx, 0);
   } else if (event.offsetY > preview.offsetHeight / 3 * 2) {
     const dy = canvas.value!.height;
     const imageData = ctx.getImageData(0, 0, canvas.value!.width, canvas.value!.height);
     canvas.value!.height += img.height;
+    canvas.value!.width = Math.max(canvas.value!.width, img.width);
     ctx.putImageData(imageData, 0, 0)
     ctx.drawImage(img, 0, dy);
   } else {
@@ -105,6 +107,7 @@ function onDrop(event: DragEvent) {
     mergeImages(current, merged.data, parseFloat(opacity));
     ctx.putImageData(merged, 0, 0);
   }
+  viable = ctx.getImageData(0, 0, canvas.value!.width, canvas.value!.height);
 }
 
 function onDragLeave() {