In what order does 'flow_from_directory' function in keras takes the samples?

Question

I'm trying to classify images into 10 classes. To get probabilities for images, I'm using model.predict_generator() function in keras. This returns only prediction values and not the corresponding sample ID(In this case image file name).

test_datagen = ImageDataGenerator(rescale=1./255)

validation_generator = test_datagen.flow_from_directory(
        '/path/',
        target_size=(256, 256),
        batch_size=32,`
        class_mode='categorical')

predictions = model.predict_generator(validation_generator, val_samples=10000)

In what order does the '.flow_from_directory' read the samples?

(OR)

How do I find the corresponding image name/id of the predictions?

Click here for the code.

Answer 1

If you set shuffle=False it looks like images are returned in whatever order os.listdir returns them in.

I just tested this by using my generator to write a few sample images to a file with shuffle=False

test_datagen = ImageDataGenerator(samplewise_center=False)

test_generator = test_datagen.flow_from_directory(
        training_config['test_data_dir'],
        target_size=(256, 256),
        batch_size=5,
        class_mode=None,
        shuffle=False,
        save_to_dir=os.path.join('samples'))

you can also print the generator's filenames.. which ( I looked at the code) just performs os.listdir

print test_generator.filenames

So, your predict_generator result at index 0 should be for the image at os.listdir index 0.