当设备性能较差时，裁剪图片有一定概率闪退

TZImagePickerController/TZImagePickerController/TZPhotoPreviewController.m

@@ -382,16 +382,23 @@
         [_tzImagePickerVc addSelectedModel:model];
     }
     if (_tzImagePickerVc.allowCrop) { // 裁剪状态
+        TZImagePickerController *rootVc = self.navigationController;
+        [rootVc showProgressHUD];
         NSIndexPath *indexPath = [NSIndexPath indexPathForItem:_currentIndex inSection:0];
         TZPhotoPreviewCell *cell = (TZPhotoPreviewCell *)[_collectionView cellForItemAtIndexPath:indexPath];
-        UIImage *cropedImage = [TZImageCropManager cropImageView:cell.previewView.imageView toRect:_tzImagePickerVc.cropRect zoomScale:cell.previewView.scrollView.zoomScale containerView:self.view];
-        if (_tzImagePickerVc.needCircleCrop) {
-            cropedImage = [TZImageCropManager circularClipImage:cropedImage];
-        }
-        if (self.doneButtonClickBlockCropMode) {
-            TZAssetModel *model = _models[_currentIndex];
-            self.doneButtonClickBlockCropMode(cropedImage,model.asset);
-        }
+        dispatch_async(dispatch_get_global_queue(0, 0), ^{
+            UIImage *cropedImage = [TZImageCropManager cropImageView:cell.previewView.imageView toRect:_tzImagePickerVc.cropRect zoomScale:cell.previewView.scrollView.zoomScale containerView:self.view];
+            if (_tzImagePickerVc.needCircleCrop) {
+                cropedImage = [TZImageCropManager circularClipImage:cropedImage];
+            }
+            dispatch_async(dispatch_get_main_queue(), ^{
+                [rootVc hideProgressHUD];
+                if (self.doneButtonClickBlockCropMode) {
+                    TZAssetModel *model = _models[_currentIndex];
+                    self.doneButtonClickBlockCropMode(cropedImage,model.asset);
+                }
+            });
+        });
     } else if (self.doneButtonClickBlock) { // 非裁剪状态
         self.doneButtonClickBlock(_isSelectOriginalPhoto);
     }