diff --git a/LICENSE b/LICENSE
index b1395e9..f1460f5 100644
--- a/LICENSE
+++ b/LICENSE
@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2020 - present, Facebook, Inc
+   Copyright 2023 - present, IDEA Research.
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
diff --git a/README.md b/README.md
index 50e516a..8704634 100644
--- a/README.md
+++ b/README.md
@@ -68,6 +68,7 @@ PyTorch implementation and pretrained models for Grounding DINO. For details, se
 
 
 ## :fire: News
+- **`2023/06/17`**: We provide an example to evaluat Grounding DINO on COCO zero-shot performance.
 - **`2023/04/15`**: Refer to [CV in the Wild Readings](https://github.com/Computer-Vision-in-the-Wild/CVinW_Readings) for those who are interested in open-set recognition!
 - **`2023/04/08`**: We release [demos](demo/image_editing_with_groundingdino_gligen.ipynb) to combine [Grounding DINO](https://arxiv.org/abs/2303.05499) with [GLIGEN](https://github.com/gligen/GLIGEN)  for more controllable image editings.
 - **`2023/04/08`**: We release [demos](demo/image_editing_with_groundingdino_stablediffusion.ipynb) to combine [Grounding DINO](https://arxiv.org/abs/2303.05499) with [Stable Diffusion](https://github.com/Stability-AI/StableDiffusion) for image editings.
@@ -129,24 +130,16 @@ cd GroundingDINO/
 Install the required dependencies in the current directory.
 
 ```bash
-pip3 install -q -e .
+pip install -e .
 ```
-Create a new directory called "weights" to store the model weights.
+
+Download pre-trained model weights.
 
 ```bash
 mkdir weights
-```
-
-Change the current directory to the "weights" folder.
-
-```bash
 cd weights
-```
-
-Download the model weights file.
-
-```bash
 wget -q https://github.com/IDEA-Research/GroundingDINO/releases/download/v0.1.0-alpha/groundingdino_swint_ogc.pth
+cd ..
 ```
 
 ## :arrow_forward: Demo
@@ -201,6 +194,19 @@ We also provide a demo code to integrate Grounding DINO with Gradio Web UI. See
 - We release [demos](demo/image_editing_with_groundingdino_gligen.ipynb) to combine [Grounding DINO](https://arxiv.org/abs/2303.05499) with [GLIGEN](https://github.com/gligen/GLIGEN)  for more controllable image editings.
 - We release [demos](demo/image_editing_with_groundingdino_stablediffusion.ipynb) to combine [Grounding DINO](https://arxiv.org/abs/2303.05499) with [Stable Diffusion](https://github.com/Stability-AI/StableDiffusion) for image editings.
 
+## COCO Zero-shot Evaluations
+
+We provide an example to evaluate Grounding DINO zero-shot performance on COCO. The results should be **48.5**.
+
+```bash
+CUDA_VISIBLE_DEVICES=0 \
+python demo/test_ap_on_coco.py \
+ -c groundingdino/config/GroundingDINO_SwinT_OGC.py \
+ -p weights/groundingdino_swint_ogc.pth \
+ --anno_path /path/to/annoataions/ie/instances_val2017.json \
+ --image_dir /path/to/imagedir/ie/val2017
+```
+
 
 ## :luggage: Checkpoints
 
diff --git a/demo/test_ap_on_coco.py b/demo/test_ap_on_coco.py
new file mode 100644
index 0000000..59ce6a2
--- /dev/null
+++ b/demo/test_ap_on_coco.py
@@ -0,0 +1,233 @@
+import argparse
+import os
+import sys
+import time
+
+import numpy as np
+import torch
+import torch.nn as nn
+from torch.utils.data import DataLoader, DistributedSampler
+
+from groundingdino.models import build_model
+import groundingdino.datasets.transforms as T
+from groundingdino.util import box_ops, get_tokenlizer
+from groundingdino.util.misc import clean_state_dict, collate_fn
+from groundingdino.util.slconfig import SLConfig
+
+# from torchvision.datasets import CocoDetection
+import torchvision
+
+from groundingdino.util.vl_utils import build_captions_and_token_span, create_positive_map_from_span
+from groundingdino.datasets.cocogrounding_eval import CocoGroundingEvaluator
+
+
+def load_model(model_config_path: str, model_checkpoint_path: str, device: str = "cuda"):
+    args = SLConfig.fromfile(model_config_path)
+    args.device = device
+    model = build_model(args)
+    checkpoint = torch.load(model_checkpoint_path, map_location="cpu")
+    model.load_state_dict(clean_state_dict(checkpoint["ema_model"]), strict=False)
+    model.eval()
+    return model
+
+
+class CocoDetection(torchvision.datasets.CocoDetection):
+    def __init__(self, img_folder, ann_file, transforms):
+        super().__init__(img_folder, ann_file)
+        self._transforms = transforms
+
+    def __getitem__(self, idx):
+        img, target = super().__getitem__(idx)  # target: list
+
+        # import ipdb; ipdb.set_trace()
+
+        w, h = img.size
+        boxes = [obj["bbox"] for obj in target]
+        boxes = torch.as_tensor(boxes, dtype=torch.float32).reshape(-1, 4)
+        boxes[:, 2:] += boxes[:, :2]  # xywh -> xyxy
+        boxes[:, 0::2].clamp_(min=0, max=w)
+        boxes[:, 1::2].clamp_(min=0, max=h)
+        # filt invalid boxes/masks/keypoints
+        keep = (boxes[:, 3] > boxes[:, 1]) & (boxes[:, 2] > boxes[:, 0])
+        boxes = boxes[keep]
+
+        target_new = {}
+        image_id = self.ids[idx]
+        target_new["image_id"] = image_id
+        target_new["boxes"] = boxes
+        target_new["orig_size"] = torch.as_tensor([int(h), int(w)])
+
+        if self._transforms is not None:
+            img, target = self._transforms(img, target_new)
+
+        return img, target
+
+
+class PostProcessCocoGrounding(nn.Module):
+    """ This module converts the model's output into the format expected by the coco api"""
+
+    def __init__(self, num_select=300, coco_api=None, tokenlizer=None) -> None:
+        super().__init__()
+        self.num_select = num_select
+
+        assert coco_api is not None
+        category_dict = coco_api.dataset['categories']
+        cat_list = [item['name'] for item in category_dict]
+        captions, cat2tokenspan = build_captions_and_token_span(cat_list, True)
+        tokenspanlist = [cat2tokenspan[cat] for cat in cat_list]
+        positive_map = create_positive_map_from_span(
+            tokenlizer(captions), tokenspanlist)  # 80, 256. normed
+
+        id_map = {0: 1, 1: 2, 2: 3, 3: 4, 4: 5, 5: 6, 6: 7, 7: 8, 8: 9, 9: 10, 10: 11, 11: 13, 12: 14, 13: 15, 14: 16, 15: 17, 16: 18, 17: 19, 18: 20, 19: 21, 20: 22, 21: 23, 22: 24, 23: 25, 24: 27, 25: 28, 26: 31, 27: 32, 28: 33, 29: 34, 30: 35, 31: 36, 32: 37, 33: 38, 34: 39, 35: 40, 36: 41, 37: 42, 38: 43, 39: 44, 40: 46,
+                  41: 47, 42: 48, 43: 49, 44: 50, 45: 51, 46: 52, 47: 53, 48: 54, 49: 55, 50: 56, 51: 57, 52: 58, 53: 59, 54: 60, 55: 61, 56: 62, 57: 63, 58: 64, 59: 65, 60: 67, 61: 70, 62: 72, 63: 73, 64: 74, 65: 75, 66: 76, 67: 77, 68: 78, 69: 79, 70: 80, 71: 81, 72: 82, 73: 84, 74: 85, 75: 86, 76: 87, 77: 88, 78: 89, 79: 90}
+
+        # build a mapping from label_id to pos_map
+        new_pos_map = torch.zeros((91, 256))
+        for k, v in id_map.items():
+            new_pos_map[v] = positive_map[k]
+        self.positive_map = new_pos_map
+
+    @torch.no_grad()
+    def forward(self, outputs, target_sizes, not_to_xyxy=False):
+        """ Perform the computation
+        Parameters:
+            outputs: raw outputs of the model
+            target_sizes: tensor of dimension [batch_size x 2] containing the size of each images of the batch
+                          For evaluation, this must be the original image size (before any data augmentation)
+                          For visualization, this should be the image size after data augment, but before padding
+        """
+        num_select = self.num_select
+        out_logits, out_bbox = outputs['pred_logits'], outputs['pred_boxes']
+
+        # pos map to logit
+        prob_to_token = out_logits.sigmoid()  # bs, 100, 256
+        pos_maps = self.positive_map.to(prob_to_token.device)
+        # (bs, 100, 256) @ (91, 256).T -> (bs, 100, 91)
+        prob_to_label = prob_to_token @ pos_maps.T
+
+        # if os.environ.get('IPDB_SHILONG_DEBUG', None) == 'INFO':
+        #     import ipdb; ipdb.set_trace()
+
+        assert len(out_logits) == len(target_sizes)
+        assert target_sizes.shape[1] == 2
+
+        prob = prob_to_label
+        topk_values, topk_indexes = torch.topk(
+            prob.view(out_logits.shape[0], -1), num_select, dim=1)
+        scores = topk_values
+        topk_boxes = topk_indexes // prob.shape[2]
+        labels = topk_indexes % prob.shape[2]
+
+        if not_to_xyxy:
+            boxes = out_bbox
+        else:
+            boxes = box_ops.box_cxcywh_to_xyxy(out_bbox)
+
+        boxes = torch.gather(
+            boxes, 1, topk_boxes.unsqueeze(-1).repeat(1, 1, 4))
+
+        # and from relative [0, 1] to absolute [0, height] coordinates
+        img_h, img_w = target_sizes.unbind(1)
+        scale_fct = torch.stack([img_w, img_h, img_w, img_h], dim=1)
+        boxes = boxes * scale_fct[:, None, :]
+
+        results = [{'scores': s, 'labels': l, 'boxes': b}
+                   for s, l, b in zip(scores, labels, boxes)]
+
+        return results
+
+
+def main(args):
+    # config
+    cfg = SLConfig.fromfile(args.config_file)
+
+    # build model
+    model = load_model(args.config_file, args.checkpoint_path)
+    model = model.to(args.device)
+    model = model.eval()
+
+    # build dataloader
+    transform = T.Compose(
+        [
+            T.RandomResize([800], max_size=1333),
+            T.ToTensor(),
+            T.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225]),
+        ]
+    )
+    dataset = CocoDetection(
+        args.image_dir, args.anno_path, transforms=transform)
+    data_loader = DataLoader(
+        dataset, batch_size=1, shuffle=False, num_workers=args.num_workers, collate_fn=collate_fn)
+
+    # build post processor
+    tokenlizer = get_tokenlizer.get_tokenlizer(cfg.text_encoder_type)
+    postprocessor = PostProcessCocoGrounding(
+        coco_api=dataset.coco, tokenlizer=tokenlizer)
+
+    # build evaluator
+    evaluator = CocoGroundingEvaluator(
+        dataset.coco, iou_types=("bbox",), useCats=True)
+
+    # build captions
+    category_dict = dataset.coco.dataset['categories']
+    cat_list = [item['name'] for item in category_dict]
+    caption = " . ".join(cat_list) + ' .'
+    print("Input text prompt:", caption)
+
+    # run inference
+    start = time.time()
+    for i, (images, targets) in enumerate(data_loader):
+        # get images and captions
+        images = images.tensors.to(args.device)
+        bs = images.shape[0]
+        input_captions = [caption] * bs
+
+        # feed to the model
+        outputs = model(images, captions=input_captions)
+
+        orig_target_sizes = torch.stack(
+            [t["orig_size"] for t in targets], dim=0).to(images.device)
+        results = postprocessor(outputs, orig_target_sizes)
+        cocogrounding_res = {
+            target["image_id"]: output for target, output in zip(targets, results)}
+        evaluator.update(cocogrounding_res)
+
+        if (i+1) % 30 == 0:
+            used_time = time.time() - start
+            eta = len(data_loader) / (i+1e-5) * used_time - used_time
+            print(
+                f"processed {i}/{len(data_loader)} images. time: {used_time:.2f}s, ETA: {eta:.2f}s")
+
+    evaluator.synchronize_between_processes()
+    evaluator.accumulate()
+    evaluator.summarize()
+
+    print("Final results:", evaluator.coco_eval["bbox"].stats.tolist())
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        "Grounding DINO eval on COCO", add_help=True)
+    # load model
+    parser.add_argument("--config_file", "-c", type=str,
+                        required=True, help="path to config file")
+    parser.add_argument(
+        "--checkpoint_path", "-p", type=str, required=True, help="path to checkpoint file"
+    )
+    parser.add_argument("--device", type=str, default="cuda",
+                        help="running device (default: cuda)")
+
+    # post processing
+    parser.add_argument("--num_select", type=int, default=300,
+                        help="number of topk to select")
+
+    # coco info
+    parser.add_argument("--anno_path", type=str,
+                        required=True, help="coco root")
+    parser.add_argument("--image_dir", type=str,
+                        required=True, help="coco image dir")
+    parser.add_argument("--num_workers", type=int, default=4,
+                        help="number of workers for dataloader")
+    args = parser.parse_args()
+
+    main(args)
diff --git a/groundingdino/datasets/cocogrounding_eval.py b/groundingdino/datasets/cocogrounding_eval.py
new file mode 100644
index 0000000..7693a18
--- /dev/null
+++ b/groundingdino/datasets/cocogrounding_eval.py
@@ -0,0 +1,269 @@
+# ------------------------------------------------------------------------
+# Grounding DINO. Midified by Shilong Liu.
+# url: https://github.com/IDEA-Research/GroundingDINO
+# Copyright (c) 2023 IDEA. All Rights Reserved.
+# Licensed under the Apache License, Version 2.0 [see LICENSE for details]
+# ------------------------------------------------------------------------
+# Copyright (c) Aishwarya Kamath & Nicolas Carion. Licensed under the Apache License 2.0. All Rights Reserved
+# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
+"""
+COCO evaluator that works in distributed mode.
+
+Mostly copy-paste from https://github.com/pytorch/vision/blob/edfd5a7/references/detection/coco_eval.py
+The difference is that there is less copy-pasting from pycocotools
+in the end of the file, as python3 can suppress prints with contextlib
+"""
+import contextlib
+import copy
+import os
+
+import numpy as np
+import pycocotools.mask as mask_util
+import torch
+from pycocotools.coco import COCO
+from pycocotools.cocoeval import COCOeval
+
+from groundingdino.util.misc import all_gather
+
+
+class CocoGroundingEvaluator(object):
+    def __init__(self, coco_gt, iou_types, useCats=True):
+        assert isinstance(iou_types, (list, tuple))
+        coco_gt = copy.deepcopy(coco_gt)
+        self.coco_gt = coco_gt
+
+        self.iou_types = iou_types
+        self.coco_eval = {}
+        for iou_type in iou_types:
+            self.coco_eval[iou_type] = COCOeval(coco_gt, iouType=iou_type)
+            self.coco_eval[iou_type].useCats = useCats
+
+        self.img_ids = []
+        self.eval_imgs = {k: [] for k in iou_types}
+        self.useCats = useCats
+
+    def update(self, predictions):
+        img_ids = list(np.unique(list(predictions.keys())))
+        self.img_ids.extend(img_ids)
+
+        for iou_type in self.iou_types:
+            results = self.prepare(predictions, iou_type)
+
+            # suppress pycocotools prints
+            with open(os.devnull, "w") as devnull:
+                with contextlib.redirect_stdout(devnull):
+                    coco_dt = COCO.loadRes(self.coco_gt, results) if results else COCO()
+
+            coco_eval = self.coco_eval[iou_type]
+
+            coco_eval.cocoDt = coco_dt
+            coco_eval.params.imgIds = list(img_ids)
+            coco_eval.params.useCats = self.useCats
+            img_ids, eval_imgs = evaluate(coco_eval)
+
+            self.eval_imgs[iou_type].append(eval_imgs)
+
+    def synchronize_between_processes(self):
+        for iou_type in self.iou_types:
+            self.eval_imgs[iou_type] = np.concatenate(self.eval_imgs[iou_type], 2)
+            create_common_coco_eval(self.coco_eval[iou_type], self.img_ids, self.eval_imgs[iou_type])
+
+    def accumulate(self):
+        for coco_eval in self.coco_eval.values():
+            coco_eval.accumulate()
+
+    def summarize(self):
+        for iou_type, coco_eval in self.coco_eval.items():
+            print("IoU metric: {}".format(iou_type))
+            coco_eval.summarize()
+
+    def prepare(self, predictions, iou_type):
+        if iou_type == "bbox":
+            return self.prepare_for_coco_detection(predictions)
+        elif iou_type == "segm":
+            return self.prepare_for_coco_segmentation(predictions)
+        elif iou_type == "keypoints":
+            return self.prepare_for_coco_keypoint(predictions)
+        else:
+            raise ValueError("Unknown iou type {}".format(iou_type))
+
+    def prepare_for_coco_detection(self, predictions):
+        coco_results = []
+        for original_id, prediction in predictions.items():
+            if len(prediction) == 0:
+                continue
+
+            boxes = prediction["boxes"]
+            boxes = convert_to_xywh(boxes).tolist()
+            scores = prediction["scores"].tolist()
+            labels = prediction["labels"].tolist()
+
+            coco_results.extend(
+                [
+                    {
+                        "image_id": original_id,
+                        "category_id": labels[k],
+                        "bbox": box,
+                        "score": scores[k],
+                    }
+                    for k, box in enumerate(boxes)
+                ]
+            )
+        return coco_results
+
+    def prepare_for_coco_segmentation(self, predictions):
+        coco_results = []
+        for original_id, prediction in predictions.items():
+            if len(prediction) == 0:
+                continue
+
+            scores = prediction["scores"]
+            labels = prediction["labels"]
+            masks = prediction["masks"]
+
+            masks = masks > 0.5
+
+            scores = prediction["scores"].tolist()
+            labels = prediction["labels"].tolist()
+
+            rles = [
+                mask_util.encode(np.array(mask[0, :, :, np.newaxis], dtype=np.uint8, order="F"))[0] 
+                for mask in masks
+            ]
+            for rle in rles:
+                rle["counts"] = rle["counts"].decode("utf-8")
+
+            coco_results.extend(
+                [
+                    {
+                        "image_id": original_id,
+                        "category_id": labels[k],
+                        "segmentation": rle,
+                        "score": scores[k],
+                    }
+                    for k, rle in enumerate(rles)
+                ]
+            )
+        return coco_results
+
+    def prepare_for_coco_keypoint(self, predictions):
+        coco_results = []
+        for original_id, prediction in predictions.items():
+            if len(prediction) == 0:
+                continue
+
+            boxes = prediction["boxes"]
+            boxes = convert_to_xywh(boxes).tolist()
+            scores = prediction["scores"].tolist()
+            labels = prediction["labels"].tolist()
+            keypoints = prediction["keypoints"]
+            keypoints = keypoints.flatten(start_dim=1).tolist()
+
+            coco_results.extend(
+                [
+                    {
+                        "image_id": original_id,
+                        "category_id": labels[k],
+                        "keypoints": keypoint,
+                        "score": scores[k],
+                    }
+                    for k, keypoint in enumerate(keypoints)
+                ]
+            )
+        return coco_results
+
+
+def convert_to_xywh(boxes):
+    xmin, ymin, xmax, ymax = boxes.unbind(1)
+    return torch.stack((xmin, ymin, xmax - xmin, ymax - ymin), dim=1)
+
+
+def merge(img_ids, eval_imgs):
+    all_img_ids = all_gather(img_ids)
+    all_eval_imgs = all_gather(eval_imgs)
+
+    merged_img_ids = []
+    for p in all_img_ids:
+        merged_img_ids.extend(p)
+
+    merged_eval_imgs = []
+    for p in all_eval_imgs:
+        merged_eval_imgs.append(p)
+
+    merged_img_ids = np.array(merged_img_ids)
+    merged_eval_imgs = np.concatenate(merged_eval_imgs, 2)
+
+    # keep only unique (and in sorted order) images
+    merged_img_ids, idx = np.unique(merged_img_ids, return_index=True)
+    merged_eval_imgs = merged_eval_imgs[..., idx]
+
+    return merged_img_ids, merged_eval_imgs
+
+
+def create_common_coco_eval(coco_eval, img_ids, eval_imgs):
+    img_ids, eval_imgs = merge(img_ids, eval_imgs)
+    img_ids = list(img_ids)
+    eval_imgs = list(eval_imgs.flatten())
+
+    coco_eval.evalImgs = eval_imgs
+    coco_eval.params.imgIds = img_ids
+    coco_eval._paramsEval = copy.deepcopy(coco_eval.params)
+
+
+#################################################################
+# From pycocotools, just removed the prints and fixed
+# a Python3 bug about unicode not defined
+#################################################################
+
+
+def evaluate(self):
+    """
+    Run per image evaluation on given images and store results (a list of dict) in self.evalImgs
+    :return: None
+    """
+    # tic = time.time()
+    # print('Running per image evaluation...')
+    p = self.params
+    # add backward compatibility if useSegm is specified in params
+    if p.useSegm is not None:
+        p.iouType = "segm" if p.useSegm == 1 else "bbox"
+        print("useSegm (deprecated) is not None. Running {} evaluation".format(p.iouType))
+    # print('Evaluate annotation type *{}*'.format(p.iouType))
+    p.imgIds = list(np.unique(p.imgIds))
+    if p.useCats:
+        p.catIds = list(np.unique(p.catIds))
+    p.maxDets = sorted(p.maxDets)
+    self.params = p
+
+    self._prepare()
+    # loop through images, area range, max detection number
+    catIds = p.catIds if p.useCats else [-1]
+
+    if p.iouType == "segm" or p.iouType == "bbox":
+        computeIoU = self.computeIoU
+    elif p.iouType == "keypoints":
+        computeIoU = self.computeOks
+    self.ious = {
+        (imgId, catId): computeIoU(imgId, catId) 
+        for imgId in p.imgIds 
+        for catId in catIds}
+
+    evaluateImg = self.evaluateImg
+    maxDet = p.maxDets[-1]
+    evalImgs = [
+        evaluateImg(imgId, catId, areaRng, maxDet) 
+        for catId in catIds 
+        for areaRng in p.areaRng 
+        for imgId in p.imgIds
+    ]
+    # this is NOT in the pycocotools code, but could be done outside
+    evalImgs = np.asarray(evalImgs).reshape(len(catIds), len(p.areaRng), len(p.imgIds))
+    self._paramsEval = copy.deepcopy(self.params)
+    # toc = time.time()
+    # print('DONE (t={:0.2f}s).'.format(toc-tic))
+    return p.imgIds, evalImgs
+
+
+#################################################################
+# end of straight copy from pycocotools, just removing the prints
+#################################################################
diff --git a/groundingdino/models/GroundingDINO/groundingdino.py b/groundingdino/models/GroundingDINO/groundingdino.py
index 052df62..a5758fd 100644
--- a/groundingdino/models/GroundingDINO/groundingdino.py
+++ b/groundingdino/models/GroundingDINO/groundingdino.py
@@ -228,7 +228,6 @@ class GroundingDINO(nn.Module):
             captions = kw["captions"]
         else:
             captions = [t["caption"] for t in targets]
-        len(captions)
 
         # encoder texts
         tokenized = self.tokenizer(captions, padding="longest", return_tensors="pt").to(
diff --git a/groundingdino/version.py b/groundingdino/version.py
deleted file mode 100644
index 3dc1f76..0000000
--- a/groundingdino/version.py
+++ /dev/null
@@ -1 +0,0 @@
-__version__ = "0.1.0"