image_sequence.py

import numpy as np;
import pandas as pd
from PIL import Image, ImageDraw, ImageFont


class ImageSequence:
    '''
    Class to hold the necessary information about the image sequence
    '''

    def __init__(self, filename):
        self.load_features(filename)

    def feat_2d(self):
        return self._feat_2d

    def length(self):
        return self._length

    def number_of_features(self):
        return self._number_of_features

    def width(self):
        return self._width

    def height(self):
        return self._height

    def load_features(self, filename):
        '''
        Method that loads a txt file containing 2D coordinates of image features. The format of each line should be:
        [x y feature_number image_number image_filename]
        '''
        features_df = pd.read_csv(filename, delimiter=r"\s+", index_col=False)
        # get length of sequence and number of features
        self._length = int(features_df['image_id'].max())
        self._number_of_features = int(features_df['feature_id'].max())

        # get the 2d features
        self.feat_2d = np.zeros(shape=[self._length, 4, self._number_of_features])
        for i in range(1, self._length + 1):
            self.feat_2d[i - 1, :, :] = np.transpose(features_df.loc[features_df['image_id'] == i].values)[0:4]

        # keep the image filenames
        self._image_filenames = features_df.image_filename.unique()

        # get the image sequence width and height
        image = Image.open(self._image_filenames[0])
        self._width = 1024  # image.width
        self._height = 768  # image.height

    def get_normalized_coordinates(self):
        '''
        Method to normalize the coordinates to the range [-1,1]
        '''
        mm = (self._width + self._height) / 2;

        rows = (self.feat_2d[:, 0] - np.ones(self.number_of_features) * self._width) / mm
        cols = (self.feat_2d[:, 1] - np.ones(self.number_of_features) * self._height) / mm
        return np.dstack((rows, cols)).swapaxes(1, 2)

    def show(self):
        '''
        Method to display the sequence, with the 2D features superimposed
        '''
        font = ImageFont.truetype('/Library/fonts/arial.ttf', 30)
        for i in range(0, self.length):
            filename = self._image_filenames[i]
            image = Image.open(filename)
            draw = ImageDraw.Draw(image)
            for j in range(0, self.number_of_features):
                x = self.feat_2d[i, :, j][0];
                y = image.height - self.feat_2d[i, :, j][1]
                draw.text((x, y), "+" + str(j), font=font, fill=(0, 255, 0))

            image.show()