Error using image: Error when checking input: expected dense_56_input to have 2 dimensions, but got array with shape

Question

I am trying to train a Sequential model using simple flow_from_directory() but i am getting this error , I have tried using lesser layers but the error dose not go away.

from keras.preprocessing.image import ImageDataGenerator
from keras.models import Sequential
from keras.layers import Dense, Flatten



train_directory = 'D:\D_data\Rock_Paper_Scissors\Train'
training_datgagen = ImageDataGenerator(rescale = 1./255)
training_generator = training_datgagen.flow_from_directory(
train_directory,
target_size = (28,28),
class_mode = 'categorical')

validation_directory = 'D:\D_data\Rock_Paper_Scissors\Test'
validation_datagen = ImageDataGenerator(rescale= 1./255)
validation_generator = validation_datagen.flow_from_directory(
validation_directory,
target_size = (28,28),
class_mode = 'categorical'
)

model = Sequential()

model.add(Dense(128, input_shape = (784,)))
model.add(Dense(64, activation = 'relu'))
model.add(Dense(16, activation = 'relu'))
model.add(Dense(3, activation = 'softmax'))

model.compile(optimizer = 'adam', loss = 'categorical_crossentropy',metrics = ['accuracy'])

model.fit_generator(training_generator,epochs=10)

Here is the error:

File "C:\Users\Ankit\.spyder-py3\temp.py", line 31, in <module>
    model.fit_generator(training_generator,epochs=10)

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\legacy\interfaces.py", line 91, in wrapper
    return func(*args, **kwargs)

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\engine\training.py", line 1732, in fit_generator
    initial_epoch=initial_epoch)

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\engine\training_generator.py", line 220, in fit_generator
    reset_metrics=False)

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\engine\training.py", line 1508, in train_on_batch
    class_weight=class_weight)

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\engine\training.py", line 579, in _standardize_user_data
    exception_prefix='input')

  File "C:\Users\Ankit\anaconda3\lib\site-packages\keras\engine\training_utils.py", line 135, in standardize_input_data
    'with shape ' + str(data_shape))

  ValueError: Error when checking input: expected dense_56_input to have 2 dimensions, but got array with shape (32, 28, 28, 3)

Answer 1

The error occurs due to mismatch in the input shape. In the model you have specified it as input_shape = (784,) but the actual images that the model is getting as input are of different size. Just put the input shape as input_shape = (32, 32, 3) and you are good to go. Take a look here for more details on how to specify the input_shape.

Also, you'll have to use convolutional layers to process images or you can use a flatten layer before using dense layers!