Symmetry or mirror function

[jruiz72]

Hi,

I've been annotating some images that have "Left" and "Right" parts where the Left part is exactly the same as the Right part but reflected. At the moment Labelme doesn't have a Mirror/Symmetry function and I think that this feature will save a lot of time. I was trying to apply something like that modifiying the Json generated by labelme, so this is my the code in Python. I think that maybe it is not the best because I'm not a senior programmer but I think it can give you ideas of how implement it.

In this code I only reflect vertically one polygon respect to the middle of my image. My image size is 1024x1024, that's why it's hard-coded. But I consider that as a general solution, the code should:

• Ask for the destination label of the reflected polygon
• Ask the user to draw a straight line to do the mirror operation
• Apply the mirror function to selected polygons not only one

You can also find ideas of how to implement this by looking at AutoCAD (Software to draw plans widely used in engineering) implementation of the mirror function. By the way, this software has a lot of cool features that can enrich Labelme such as rotating figures, merge polygons, scale objects, etc.

import json

Archivo = "Path of the Json file"

with open(Archivo) as f:
    data = json.load(f)

points = data['shapes'][0]['points']

center_x = 512 #All my images are 1024x1024 

symmetric_points = []
for point in points:
    symmetric_x = center_x - (point[0] - center_x)
    symmetric_y = point[1]
    symmetric_points.append([symmetric_x, symmetric_y])

# Add reflected polygon to data
data['shapes'].append({
    'label': data['shapes'][0]['label'],
    'points': symmetric_points,
    'group_id': data['shapes'][0]['group_id'],
    'shape_type': data['shapes'][0]['shape_type'],
    'flags': data['shapes'][0]['flags']
})

# Save JSON
with open(Archivo, 'w') as f:
    json.dump(data, f)