HOW_TO_EXTEND.md

ROI Picker Extension Examples

How to Support Your File Format

You can extend ROIPicker to support your own file format. The file input/output is fully done by two member functions as follows.

• ROIPicker.read_roi_file(self, filename): Reading filename and return its ROI data
• ROIPicker.write_roi_file(self, filename, roi_data): Writing roi_data to filename

📝 Note) Please remember that the ROI data (and return value roi_data) need to contains necessary properties of each ROI. Each ROI needs to have following properties at least.

• id (type int): ROI identifier (e.g. 1)
• type (type: str): points or line or polygon
• color (type: tuple): RGB or BGR color tuple (e.g. (255, 127, 0))
• pts (type: list): A series of points (e.g. [(3, 29), (10, 18)])

In Python, roi_data is a list of each ROI properties as like following example.

roi_data = [{'id': 1, 'type': 'points', 'color': (255, 127, 0), 'pts': [(3, 29), (10, 18)]},
            {'id': 2, 'type': 'line', '  color': (0, 127, 255), 'pts': [(10, 27), (5, 12)]}]

To support your file format, you can create your own class by inheriting ROIPicker and overriding two functions. For example, your file is a CSV file which contains only points as a series of id, x, y. A point can have a unique id. This means that every ROI consists of a single point.

import numpy as np
from roi_picker import ROIPicker, randcolor

class ROIPickerCSV(ROIPicker):
    '''ROI Picker with CSV files'''

    def read_roi_file(self, filename):
        '''Read ROI data from the given CSV file `filename`'''
        id_pts = np.loadtxt(filename, delimiter=',')
        roi_data = [{'id': int(id), 'type': 'points', 'color': randcolor(), 'pts': [(x, y)]}
                    for (id, x, y) in id_pts]
        return roi_data

    def write_roi_file(self, filename, roi_data):
        '''Write the given ROI data to the given CSV file `filename`'''
        id_pts = [(roi['id'], pt[0], pt[1]) for roi in roi_data for pt in roi['pts']]
        return np.savetxt(filename, id_pts, delimiter=',')

if __name__ == '__main__':
    roi_picker = ROIPickerCSV('example.jpg', 'example.csv')
    roi_picker.run_gui()