Converting circles into polygons in a .json file

Question

I've a .json file which has annotations (in terms of circles and polygons) of objects I want to train my neural network with. The problem is however the traning code only accepts polygons from the .json file, thus giving an error since mine has circles.

Does anyone know how to convert circles into polygons?

I've already tried some solutions (like below) which did not work:

import json
from pprint import pprint

with open('via_region_data(val).json') as f:
    data = json.load(f)

    for attr, val in data.items():
        for attr2, val2 in val.items():
            if attr2 == 'regions':
                for attr3, val3 in val2.items():
                    if val3['shape_attributes']['name'] == 'circle':
                        cx = val3['shape_attributes']['cx']
                        cy = val3['shape_attributes']['cy']
                        r = val3['shape_attributes']['r']
                        all_points_x = [cx, cx - 1.5 * r, cx, cx + 1.5 * r, cx]
                        all_points_y = [cy - 1.5 * r, cy, cy + 1.5 * r, cy, cy - 1.5 * r]
                        val3['shape_attributes']['cx'] = all_points_x
                        val3['shape_attributes']['cy'] = all_points_y

                        val3['shape_attributes']['all_points_x'] = val3['shape_attributes'].pop('cx')
                        val3['shape_attributes']['all_points_y'] = val3['shape_attributes'].pop('cy')
                        val3['shape_attributes']['name'] = 'polygon'


pprint(data)

with open('via_region_data-val.json', 'w') as f:
    json.dump(data, f)

throwing:

Traceback (most recent call last):
  File "polygon_fixer.py", line 10, in <module>
    for attr3, val3 in val2.items():
AttributeError: 'list' object has no attribute 'items'

Any thoughts?

P.S: Well apparently some people didn't understand that it is a .JSON file which I am trying to operate with. So here it is.

What does that have to do with JSON? That's like adding a "monday" tag because today is Monday. — Ulrich Eckhardt, Sep 17 '18 at 08:03
The problem is converting a circle definition into a polygonal equivalent. Putting that generated data into a particular JSON format is secondary (and fairly trivial). To solve the first, consider using the [parametric equation of a circle](https://en.wikipedia.org/wiki/Parametric_equation#Circle) as means to compute a series of points along the its outer edge. — martineau, Sep 17 '18 at 09:08
Your question also does not provide clear definitions of the JSON format for the two kinds of shapes (circle and polygon) being input as well as that of polygonal elements in the output. Know this is essential to solving the problem. — martineau, Sep 17 '18 at 09:19
@martineau I uploaded the whole file, it has circles and polygons inside, not sure what's still not given or defined. — Schütze, Sep 17 '18 at 10:23
The file you unloaded contains only circles and **ploylines**. It has no ploygons in it so the shape attributes associated with that kind element can't be determined by just looking at it. — martineau, Sep 18 '18 at 15:26

score 0 · Accepted Answer · answered Sep 19 '18 at 13:05

There were two problems regarding this issue.

The solution @martineau offered has to be applied. However this is not enough.
The annotation tool VIA has changed JSON formatting in later versions, apparently. Now instead of a dictionary, "regions" has a list. This means, if you somehow try to read them into polygons you need to remove '.values()' addition in your line, which should look like the following in any occasion.

polygons = [r['shape_attributes'] for r in a['regions']]
names = [r['region_attributes'] for r in a['regions']]

and not

polygons = [r['shape_attributes'] for r in a['regions'].values()]
names = [r['region_attributes'] for r in a['regions'].values()]

Converting circles into polygons in a .json file

1 Answers1