COCO Formatの作り方

# 0. 概要
あらゆる最新のアルゴリズムの評価にCOCOのデータセットが用いられている。すなわち、学習も識別もCOCOフォーマットに最適化されている。自身の画像をCOCOフォーマットで作っておけば、サクッと入れ替えられるため便利である。

# 1. フォーマット

以下の全体フォーマットを基に作成していく。
今回はセグメンテーション用にフルモデルを作成する。

```
{
    "info": {...},
    "licenses": [...],
    "images": [...],
    "annotations": [...],
    "categories": [...], <-- Not in Captions annotations
    "segment_info": [...] <-- Only in Panoptic annotations
}
```

## Info

あってもなくてもといった感じ。

```
"info": {
    "description": "COCO 2017 Dataset",
    "url": "http://cocodataset.org",
    "version": "1.0",
    "year": 2017,
    "contributor": "COCO Consortium",
    "date_created": "2017/09/01"
}
```

以下、Pythonコード

``` python
import json
import collections as cl


def info():
  tmp = cl.OrderedDict()
  tmp["description"] = "Test"
  tmp["url"] = "https://test"
  tmp["version"] = "0.01"
  tmp["year"] = 2019
  tmp["contributor"] = "xxxx"
  tmp["data_created"] = "2019/09/10"
  return tmp


def main():
    query_list = ["info", "licenses", "images", "annotations", "categories", "segment_info"]
    js = cl.OrderedDict()
    for i in range(len(query_list)):
      tmp = ""
      # Info
      if query_list[i] == "info":
        tmp = info()

      # save it
      js[query_list[i]] = tmp

    # write
    fw = open('datasets.json','w')
    json.dump(js,fw,indent=2)

if __name__=='__main__':
    main()
```

## Licenses

あってもなくてもといった感じ。`images`で参照される。

```
"licenses": [
    {
        "url": "http://creativecommons.org/licenses/by-nc-sa/2.0/",
        "id": 1,
        "name": "Attribution-NonCommercial-ShareAlike License"
    },
    {
        "url": "http://creativecommons.org/licenses/by-nc/2.0/",
        "id": 2,
        "name": "Attribution-NonCommercial License"
    },
    ...
]
```

以下、Pythonコード

``` python
def licenses():
  tmp = cl.OrderedDict()
  tmp["id"] = 1
  tmp["url"] = dummy_words
  tmp["name"] = "administrater"
  return tmp
```

## images

基本的に`id`はユニークで、後のAnnotation等に関連づけられる。

```
"images": [
    {
        "license": 4,
        "file_name": "000000397133.jpg",
        "coco_url": "http://images.cocodataset.org/val2017/000000397133.jpg",
        "height": 427,
        "width": 640,
        "date_captured": "2013-11-14 17:02:52",
        "flickr_url": "http://farm7.staticflickr.com/6116/6255196340_da26cf2c9e_z.jpg",
        "id": 397133
    },
    {
        "license": 1,
        "file_name": "000000037777.jpg",
        "coco_url": "http://images.cocodataset.org/val2017/000000037777.jpg",
        "height": 230,
        "width": 352,
        "date_captured": "2013-11-14 20:55:31",
        "flickr_url": "http://farm9.staticflickr.com/8429/7839199426_f6d48aa585_z.jpg",
        "id": 37777
    },
    ...
]
```

以下、Pythonコード

``` python
def images():
  tmps = []
  for i in range(10):
    tmp = cl.OrderedDict()
    tmp["license"] = 0
    tmp["id"] = i
    tmp["file_name"] = str(i) + ".png"
    tmp["width"] = "640"
    tmp["height"] = "480"
    tmp["date_captured"] = "2019-09-01 12:34:56"
    tmp["coco_url"] = dummy_words
    tmp["flickr_url"] = dummy_words
    tmps.append(tmp)
  return tmps
```

## annotations

`iscrowd=1`の場合は人などが沢山写っている領域全域をbboxでマスクし、segmentationエリアは`counts`と`size`が追加される。

Segmentationの並び順は`[x1, y1, x2, y2...]`とポリゴンが続いていく。1つの対象物が切れる(自転車に跨り、自転車が不連続になる)場合は`[x1, y1, ...] [x1, y1, ...]`。`area`はピクセル数でピクセルをまたがるポリゴンを描く場合小数点も出てくる。

`bbox`は`x, y, width, height`である。基本的には`min(poly_x), min(poly_y), max(poly_x) - min(poly_x), max(poly_y) - min(poly_y)`でpolygonから計算できる。


```
"annotations": [
    {
        "segmentation": [[510.66,423.01,511.72,420.03,...,510.45,423.01]],
        "area": 702.1057499999998,
        "iscrowd": 0,
        "image_id": 289343,
        "bbox": [473.07,395.93,38.65,28.67],
        "category_id": 18,
        "id": 1768
    },
    ...
    {
        "segmentation": {
            "counts": [179,27,392,41,…,55,20],
            "size": [426,640]
        },
        "area": 220834,
        "iscrowd": 1,
        "image_id": 250282,
        "bbox": [0,34,639,388],
        "category_id": 1,
        "id": 900100250282
    }
]
```

以下、Pythonコード

``` python
def annotations():
  tmps = []
  for i in range(10):
    tmp = cl.OrderedDict()
    
    tmp_segmentation = cl.OrderedDict()
    tmp_segmentation = [[10, 8]]
    tmp["segmentation"] = tmp_segmentation
    tmp["id"] = int(str(1000)+ str(i))
    tmp["image_id"] = i
    tmp["category_id"] = 62
    tmp["area"] = 10
    tmp["iscrowd"] = 0
    tmp["bbox"] =  [10, 10]
    tmps.append(tmp)
  return tmps
```

## categories
`supercategory`が大きなクラスの名前。`name`がその配下。
もし、構成品がある場合は、`keypoints`で指定、それらのつながりは`skelton`で指定する。

```json
"categories": [
    {
        "supercategory": "person",
        "id": 1,
        "name": "person",
        "keypoints": [
            "nose","left_eye","right_eye","left_ear","right_ear",
            "left_shoulder","right_shoulder","left_elbow","right_elbow",
            "left_wrist","right_wrist","left_hip","right_hip",
            "left_knee","right_knee","left_ankle","right_ankle"
        ],
        "skeleton": [
            [16,14],[14,12],[17,15],[15,13],[12,13],[6,12],[7,13],[6,7],
            [6,8],[7,9],[8,10],[9,11],[2,3],[1,2],[1,3],[2,4],[3,5],[4,6],[5,7]
        ]
    }
]
```

以下、Pythonコード

``` python
def categories():
  tmps = []
  sup = ["animal", "pill"]
  cat = ["dog", "allergy"]
  for i in range(2):
    tmp = cl.OrderedDict()
    tmp["id"] = str(i)
    tmp["supercategory"] = sup[i]
    tmp["name"] = cat[i]
    tmps.append(tmp)
  return tmps
```

# 2. Visualize
完成予想像
![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/95636/667de7a3-59ab-b3c8-2181-9a9a0fa57cf7.png)

Jupyterで以下のようなコードを書く。

基本は以下のコードを改変
https://gist.github.com/akTwelve/dc79fc8b9ae66828e7c7f648049bc42d#file-coco_image_viewer-ipynb
オンライン上から参照できる画像しか上手く表示できないのでBase64エンコーディングしてオフライン画像の表示も対応させた。

``` python
import IPython
import os
import json
import random
import numpy as np
import requests
from io import BytesIO
from math import trunc
from PIL import Image as PILImage
from PIL import ImageDraw as PILImageDraw
import base64


# Load the dataset json
class CocoDataset():
    def __init__(self, annotation_path, image_dir):
        self.annotation_path = annotation_path
        self.image_dir = image_dir
        self.colors = colors = ['blue', 'purple', 'red', 'green', 'orange', 'salmon', 'pink', 'gold',
                                'orchid', 'slateblue', 'limegreen', 'seagreen', 'darkgreen', 'olive',
                               'teal', 'aquamarine', 'steelblue', 'powderblue', 'dodgerblue', 'navy',
                               'magenta', 'sienna', 'maroon']
        
        json_file = open(self.annotation_path)
        self.coco = json.load(json_file)
        json_file.close()
        
        self.process_info()
        self.process_licenses()
        self.process_categories()
        self.process_images()
        self.process_segmentations()
            
        
    def display_info(self):
        print('Dataset Info:')
        print('=============')
        for key, item in self.info.items():
            print('  {}: {}'.format(key, item))
        
        requirements = [['description', str],
                        ['url', str],
                        ['version', str],
                        ['year', int],
                        ['contributor', str],
                        ['date_created', str]]
        for req, req_type in requirements:
            if req not in self.info:
                print('ERROR: {} is missing'.format(req))
            elif type(self.info[req]) != req_type:
                print('ERROR: {} should be type {}'.format(req, str(req_type)))
        print('')

        
    def display_licenses(self):
        print('Licenses:')
        print('=========')
        
        requirements = [['id', int],
                        ['url', str],
                        ['name', str]]
        for license in self.licenses:
            for key, item in license.items():
                print('  {}: {}'.format(key, item))
            for req, req_type in requirements:
                if req not in license:
                    print('ERROR: {} is missing'.format(req))
                elif type(license[req]) != req_type:
                    print('ERROR: {} should be type {}'.format(req, str(req_type)))
            print('')
        print('')
        
    def display_categories(self):
        print('Categories:')
        print('=========')
        for sc_key, sc_val in self.super_categories.items():
            print('  super_category: {}'.format(sc_key))
            for cat_id in sc_val:
                print('    id {}: {}'.format(cat_id, self.categories[cat_id]['name']))
            print('')
    
    def display_image(self, image_id, show_polys=True, show_bbox=True, show_crowds=True, use_url=False):
        print('Image:')
        print('======')
        if image_id == 'random':
            image_id = random.choice(list(self.images.keys()))
        
        # Print the image info
        image = self.images[image_id]
        for key, val in image.items():
            print('  {}: {}'.format(key, val))

        # Open the image
        if use_url:
            image_path = image['coco_url']
            response = requests.get(image_path)
            image = PILImage.open(BytesIO(response.content))
            
        else:
            image_path = os.path.join(self.image_dir, image['file_name'])
            image = PILImage.open(image_path)
            
        
        # Calculate the size and adjusted display size
        max_width = 600
        image_width, image_height = image.size
        adjusted_width = min(image_width, max_width)
        adjusted_ratio = adjusted_width / image_width
        adjusted_height = adjusted_ratio * image_height
        
        # Create list of polygons to be drawn
        polygons = {}
        bbox_polygons = {}
        rle_regions = {}
        poly_colors = {}
        print('  segmentations ({}):'.format(len(self.segmentations[image_id])))
        for i, segm in enumerate(self.segmentations[image_id]):
            polygons_list = []
            if segm['iscrowd'] != 0:
                # Gotta decode the RLE
                px = 0
                x, y = 0, 0
                rle_list = []
                for j, counts in enumerate(segm['segmentation']['counts']):
                    if j % 2 == 0:
                        # Empty pixels
                        px += counts
                    else:
                        # Need to draw on these pixels, since we are drawing in vector form,
                        # we need to draw horizontal lines on the image
                        x_start = trunc(trunc(px / image_height) * adjusted_ratio)
                        y_start = trunc(px % image_height * adjusted_ratio)
                        px += counts
                        x_end = trunc(trunc(px / image_height) * adjusted_ratio)
                        y_end = trunc(px % image_height * adjusted_ratio)
                        if x_end == x_start:
                            # This is only on one line
                            rle_list.append({'x': x_start, 'y': y_start, 'width': 1 , 'height': (y_end - y_start)})
                        if x_end > x_start:
                            # This spans more than one line
                            # Insert top line first
                            rle_list.append({'x': x_start, 'y': y_start, 'width': 1, 'height': (image_height - y_start)})
                            
                            # Insert middle lines if needed
                            lines_spanned = x_end - x_start + 1 # total number of lines spanned
                            full_lines_to_insert = lines_spanned - 2
                            if full_lines_to_insert > 0:
                                full_lines_to_insert = trunc(full_lines_to_insert * adjusted_ratio)
                                rle_list.append({'x': (x_start + 1), 'y': 0, 'width': full_lines_to_insert, 'height': image_height})
                                
                            # Insert bottom line
                            rle_list.append({'x': x_end, 'y': 0, 'width': 1, 'height': y_end})
                if len(rle_list) > 0:
                    rle_regions[segm['id']] = rle_list  
            else:
                # Add the polygon segmentation
                for segmentation_points in segm['segmentation']:
                    segmentation_points = np.multiply(segmentation_points, adjusted_ratio).astype(int)
                    polygons_list.append(str(segmentation_points).lstrip('[').rstrip(']'))
            polygons[segm['id']] = polygons_list
            if i < len(self.colors):
                poly_colors[segm['id']] = self.colors[i]
            else:
                poly_colors[segm['id']] = 'white'
            
            bbox = segm['bbox']
            bbox_points = [bbox[0], bbox[1], bbox[0] + bbox[2], bbox[1],
                           bbox[0] + bbox[2], bbox[1] + bbox[3], bbox[0], bbox[1] + bbox[3],
                           bbox[0], bbox[1]]
            bbox_points = np.multiply(bbox_points, adjusted_ratio).astype(int)
            bbox_polygons[segm['id']] = str(bbox_points).lstrip('[').rstrip(']')
            
            # Print details
            print('    {}:{}:{}'.format(segm['id'], poly_colors[segm['id']], self.categories[segm['category_id']]))
        
        # tif to png
        image.convert(mode="I")
        image.save("./tmp.png", "png")
        image = PILImage.open("./tmp.png")
        with open("tmp.png", 'rb') as f:
            data = f.read()
            # base64
            b64=base64.b64encode(data)            
        img_b64 = "data:image/png;base64,"+ b64.decode('utf-8') # binary to string
        html  = '<div class="container" style="position:relative;">'
        html += '<img src="{}" style="position:relative;top:0px;left:0px;width:{}px;">'.format(img_b64, adjusted_width)
        html += '<div class="svgclass"><svg width="{}" height="{}">'.format(adjusted_width, adjusted_height)
        
        if show_polys:
            for seg_id, points_list in polygons.items():
                fill_color = poly_colors[seg_id]
                stroke_color = poly_colors[seg_id]
                for points in points_list:
                    html += '<polygon points="{}" style="fill:{}; stroke:{}; stroke-width:1; fill-opacity:0.5" />'.format(points, fill_color, stroke_color)
        
        if show_crowds:
            for seg_id, rect_list in rle_regions.items():
                fill_color = poly_colors[seg_id]
                stroke_color = poly_colors[seg_id]
                for rect_def in rect_list:
                    x, y = rect_def['x'], rect_def['y']
                    w, h = rect_def['width'], rect_def['height']
                    html += '<rect x="{}" y="{}" width="{}" height="{}" style="fill:{}; stroke:{}; stroke-width:1; fill-opacity:0.5; stroke-opacity:0.5" />'.format(x, y, w, h, fill_color, stroke_color)
            
        if show_bbox:
            for seg_id, points in bbox_polygons.items():
                fill_color = poly_colors[seg_id]
                stroke_color = poly_colors[seg_id]
                html += '<polygon points="{}" style="fill:{}; stroke:{}; stroke-width:1; fill-opacity:0" />'.format(points, fill_color, stroke_color)
                
        html += '</svg></div>'
        html += '</div>'
        html += '<style>'
        html += '.svgclass { position:absolute; top:0px; left:0px;}'
        html += '</style>'
        return html
       
    def process_info(self):
        self.info = self.coco['info']
    
    def process_licenses(self):
        self.licenses = self.coco['licenses']
    
    def process_categories(self):
        self.categories = {}
        self.super_categories = {}
        for category in self.coco['categories']:
            cat_id = category['id']
            super_category = category['supercategory']
            
            # Add category to the categories dict
            if cat_id not in self.categories:
                self.categories[cat_id] = category
            else:
                print("ERROR: Skipping duplicate category id: {}".format(category))

            # Add category to super_categories dict
            if super_category not in self.super_categories:
                self.super_categories[super_category] = {cat_id} # Create a new set with the category id
            else:
                self.super_categories[super_category] |= {cat_id} # Add category id to the set
                
    def process_images(self):
        self.images = {}
        for image in self.coco['images']:
            image_id = image['id']
            if image_id in self.images:
                print("ERROR: Skipping duplicate image id: {}".format(image))
            else:
                self.images[image_id] = image
                
    def process_segmentations(self):
        self.segmentations = {}
        for segmentation in self.coco['annotations']:
            image_id = segmentation['image_id']
            if image_id not in self.segmentations:
                self.segmentations[image_id] = []
            self.segmentations[image_id].append(segmentation)
```

ヘッダの表示

``` python
annotation_path = 'ANNO_PATH'
image_dir = 'IMG_PATH'

coco_dataset = CocoDataset(annotation_path, image_dir)
coco_dataset.display_info()
coco_dataset.display_licenses()
coco_dataset.display_categories()
```

画像IDを指定して表示

``` python
html = coco_dataset.display_image(1)
IPython.display.HTML(html)
```