[cherry-pick]modify VOCDataSet and default value of allow_empty (#4097)

* modify VOCDataSet and default value of allow_empty

* revert default value of allow_empty (#4150)
Co-authored-by: Nwangguanzhong <jerrywgz@126.com>

ppdet/data/source/coco.py

@@ -242,7 +242,7 @@ class COCODataSet(DetDataset):
                 break
         assert ct > 0, 'not found any coco record in %s' % (anno_path)
         logger.debug('{} samples in file {}'.format(ct, anno_path))
-        if len(empty_records) > 0:
+        if self.allow_empty and len(empty_records) > 0:
             empty_records = self._sample_empty(empty_records, len(records))
             records += empty_records
         self.roidbs = records

ppdet/data/source/voc.py

@@ -131,11 +131,13 @@ class VOCDataSet(DetDataset):
                         'Illegal width: {} or height: {} in annotation, '
                         'and {} will be ignored'.format(im_w, im_h, xml_file))
                     continue
-                gt_bbox = []
-                gt_class = []
-                gt_score = []
-                difficult = []
-                for i, obj in enumerate(objs):
+
+                num_bbox, i = len(objs), 0
+                gt_bbox = np.zeros((num_bbox, 4), dtype=np.float32)
+                gt_class = np.zeros((num_bbox, 1), dtype=np.int32)
+                gt_score = np.zeros((num_bbox, 1), dtype=np.float32)
+                difficult = np.zeros((num_bbox, 1), dtype=np.int32)
+                for obj in objs:
                     cname = obj.find('name').text
 
                     # user dataset may not contain difficult field
@@ -152,19 +154,20 @@ class VOCDataSet(DetDataset):
                     x2 = min(im_w - 1, x2)
                     y2 = min(im_h - 1, y2)
                     if x2 > x1 and y2 > y1:
-                        gt_bbox.append([x1, y1, x2, y2])
-                        gt_class.append([cname2cid[cname]])
-                        gt_score.append([1.])
-                        difficult.append([_difficult])
+                        gt_bbox[i, :] = [x1, y1, x2, y2]
+                        gt_class[i, 0] = cname2cid[cname]
+                        gt_score[i, 0] = 1.
+                        difficult[i, 0] = _difficult
+                        i += 1
                     else:
                         logger.warning(
                             'Found an invalid bbox in annotations: xml_file: {}'
                             ', x1: {}, y1: {}, x2: {}, y2: {}.'.format(
                                 xml_file, x1, y1, x2, y2))
-                gt_bbox = np.array(gt_bbox).astype('float32')
-                gt_class = np.array(gt_class).astype('int32')
-                gt_score = np.array(gt_score).astype('float32')
-                difficult = np.array(difficult).astype('int32')
+                gt_bbox = gt_bbox[:i, :]
+                gt_class = gt_class[:i, :]
+                gt_score = gt_score[:i, :]
+                difficult = difficult[:i, :]
 
                 voc_rec = {
                     'im_file': img_file,
@@ -193,7 +196,7 @@ class VOCDataSet(DetDataset):
                     break
         assert ct > 0, 'not found any voc record in %s' % (self.anno_path)
         logger.debug('{} samples in file {}'.format(ct, anno_path))
-        if len(empty_records) > 0:
+        if self.allow_empty and len(empty_records) > 0:
             empty_records = self._sample_empty(empty_records, len(records))
             records += empty_records
         self.roidbs, self.cname2cid = records, cname2cid