Develop Reference

My CNN model accuracy is not improving with ResNet50

I'm working on a machine learning project with TensorFlow for sign language recognition.
When I first tried to build my CNN model it has a validation accuracy of 94% :
def create_model():
model = Sequential(name='SIGNS_LANGUAGE')
model.add(layers.Conv2D(32,(3,3),activation='relu',input_shape=(IMG_SIZE, IMG_SIZE , 3) ) )
model.add(layers.MaxPooling2D(pool_size = (2, 2)))
model.add(layers.Conv2D(64, (3, 3), activation='relu' ,input_shape=(IMG_SIZE, IMG_SIZE , 3) ) )
model.add(layers.MaxPooling2D(pool_size = (2, 2)))
#classification layers
model.add(layers.Flatten())
model.add(layers.Dense(512, activation='relu'))
model.add(layers.Dropout(0.2))
model.add(layers.Dense(512, activation='relu'))
model.add(layers.Dropout(0.2))
model.add(layers.Dense(512, activation='relu'))
model.add(layers.Dropout(0.2))
model.add(layers.Dense(targetCount, activation='softmax'))
print(model.summary())
return model`
BUT IT HASN'T BEEN GOOD AT generalizing with a different data.
So I tried to work with a pre-trained model like ResNet50 but I couldn't figure out why the accuracy is not improving with time, it hit 40% and stopped:
def create_model():
model = Sequential(name='SIGNS')
input_shape = (IMG_SIZE , IMG_SIZE , 3)
res_layer = tf.keras.applications.ResNet50(input_shape=input_shape, include_top=False , weights='imagenet' )
res_layer.trainable = False
model.add( res_layer )
model.add(layers.GlobalAveragePooling2D())
model.add(layers.Dropout(0.2))
model.add(layers.Dense(1024, activation='relu'))
model.add(layers.Dropout(0.2))
model.add(layers.Dense(512, activation='relu'))
model.add(layers.Dropout(0.2))
model.add(layers.Dense(targetCount, activation='softmax'))
print(model.summary())
return model
Any suggestions on how to improve the model??
N.B: I input 54049 grayscale images in the 3 channels and I use Adam optimizer.

If you are using a pre-trained architecture, you have to normalize your data according to the dataset on which the pre-trained architecture was originally trained on(in this case, Imagenet).
Try incorporating this code after your first one -
preprocessing_layer = tf.keras.applications.resnet50.preprocess_input(x, data_format=None)
inputs = keras.Input(shape=input_shape)
x = preprocessing_layer(inputs)
outputs = model(x)
inference_model = keras.Model(inputs, outputs)

How do i access data after model.add(Flatten()) layer?

I am trying to use CNN for feature extraction and XGboost for classification of a image data. I researched and found that it could be done by extracting the data after the convolution layers. I found some source code for similar problem and tried on my own.
model = Sequential()
model.add(Conv2D(32, kernel_size=(3,3), strides=(1,1), padding='same', activation="relu", input_shape = data.shape[1:]))
model.add(MaxPool2D(pool_size=(2,2), strides=(2,2)))
model.add(Conv2D(64, kernel_size=(3,3), padding='same', strides=(1,1), activation="relu") )
model.add(MaxPool2D(pool_size=(2,2), strides=(2,2))) #max pool window 2x2
model.add(Conv2D(128, kernel_size=(3,3), padding='same', strides=(1,1), activation="relu"))
model.add(MaxPool2D(pool_size=(2,2), strides=(2,2))) #max pool window 2x2
model.add(Conv2D(256, kernel_size=(3,3), padding='same', strides=(1,1), activation="relu"))
model.add(MaxPool2D(pool_size=(2,2), strides=(2,2))) #max pool window 2x2
model.add(Flatten())
model.add(Dense(128, activation="relu", name='firstDenseLayer'))
model.add(Dense(1, activation="sigmoid"))
# model.summary()
# print(model)
model.compile(loss="binary_crossentropy", optimizer="adam", metrics=["accuracy"])
model.fit(data, label, batch_size=16, epochs=10, validation_data=(val_data, val_label))
Below i accessed the dense layer named "firstDenseLayer".
import xgboost as xgb
from keras.models import Model
layerName = 'firstDenseLayer'
intermediate_layer_model = Model(inputs=model.input,
outputs=model.get_layer(layerName).output)
intermediate_output = intermediate_layer_model.predict(data)
from xgboost import XGBClassifier
xgbmodel = XGBClassifier(objective='multi:softmax', num_class= 2)
xgbmodel.fit(intermediate_output, label)
xgbmodel.score(intermediate_output, label)
As i am new in this, i have several confusions.
How the data is being flowed. After i extract the features of the pictures via convolution layers, how do i actually access the data from there?
What is this line of code doing? What data is it extracting?
intermediate_output = intermediate_layer_model.predict(data)
When i omit(keep commented out) the below line,
model.fit(data, label, batch_size=16, epochs=10, validation_data=(val_data, val_label))
from the first snippet and run the XGboost model directly the XGboost gives low accuracy and when i don't it gives higher accuracy. Why is it being like that?
Kindly help me out. I am stuck with this for quite a while. I am just trying to access the extracted features data from the last convolution layer and use that data to do classification using XGboost. As i tried to follow the method that i found from online, i am not sure if it is the the only way of doing it. If there is another way kindly let me know.

The model.fit(...) line does what you would expect, it trains the convnet defined by model on some data and labels. Your classifier yielding lower accuracy when you're using randomly initialized weights (i.e. without running fit) is not surprising.
intermediate_layer_model is constructed as a keras model whose output is the dense layer just before the output of model. Note the name parameter given to the dense layer in the construction of model.
You could just as easily give a name to one of the Conv2D layers and access it the same way. Alternatively, you could store the layer in a python variable, i.e. instead of
model.add(Conv2D(256, kernel_size=(3,3), padding='same', strides=(1,1), activation="relu"))
in the model construction it could say
last_conv_layer = Conv2D(256, kernel_size=(3,3), padding='same', strides=(1,1), activation="relu")
model.add(last_conv_layer)
Then for the intermediate_layer_model you put
intermediate_layer_model = Model(inputs=model.input, outputs=last_conv_layer.output)

CONV1D NEURAL NETWORK SHAPE

model = Sequential()
model.add(Conv1D(filters=4, kernel_size=(1), activation="relu", input_shape=(4,1)))
model.add(MaxPooling1D(pool_size=(1)))
model.add(Dropout(0.25))
model.add(Conv1D(filters=32, kernel_size=(1), activation='relu'))
model.add(MaxPooling1D(pool_size=(1)))
model.add(Dropout(0.25))
model.add(Conv1D(filters=64, kernel_size=(1), activation="relu"))
model.add(MaxPooling1D(pool_size=(1)))
model.add(Dropout(0.25))
model.add(Conv1D(filters=64, kernel_size=(1), activation='relu'))
model.add(MaxPooling1D(pool_size=(1)))
model.add(Dropout(0.25))
model.add(Flatten())
model.add(Dense(128, activation='relu'))
model.add(Dropout(0.5))
model.add(Dense(64, activation='relu'))
model.add(Dropout(0.5))
model.add(Flatten())
model.add(Dense(7, activation='sigmoid'))
model.compile(optimizer='adam', loss='binary_crossentropy', metrics=['accuracy'])
Hello, I'm new to building neural networks and decided to try my hand solving a multi-label classification problem. I'm take four feature values as input and giving the resulting classification as one or more of 7 categories. As such, I decided to implement the neural network as seen above.
However, upon fitting the model
model.fit(X_train, y_train, epochs = 10, validation_data = (X_test,y_test), batch_size = 64)
I receive this error:
Error when checking input: expected conv1d_92_input to have 3 dimensions, but got array with shape (415, 4)
I'm confused as to watch to do in order to get the neural network to fit to the data. The shape of feature and label data respectively are :
X_train = (414,4)
y_train = (413,7)

I believe you might find this previous stack stackoverflow post (It seems to be addressing your question) helpful: Error when checking model input: expected lstm_1_input to have 3 dimensions, but got array with shape (339732, 29)

CNN architecture: classifying "good" and "bad" images

I'm researching the possibility of implementing a CNN in order to classify images as "good" or "bad" but am having no luck with my current architecture.
Characteristics that denote a "bad" image:
Overexposure
Oversaturation
Incorrect white balance
Blurriness
Would it be feasible to implement a neural network to classify images based on these characteristics or is it best left to a traditional algorithm that simply looks at the variance in brightness/contrast throughout an image and classifies it that way?
I have attempted training a CNN using the VGGNet architecture but I always seem to get a biased and unreliable model, regardless of the number of epochs or number of steps.
Examples:
My current model's architecture is very simple (as I am new to the whole machine learning world) but seemed to work fine with other classification problems, and I have modified it slightly to work better with this binary classification problem:
# CONV => RELU => POOL layer set
# define convolutional layers, use "ReLU" activation function
# and reduce the spatial size (width and height) with pool layers
model.add(Conv2D(32, (3, 3), padding="same", input_shape=input_shape)) # 32 3x3 filters (height, width, depth)
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(MaxPooling2D(pool_size=(2,2)))
model.add(Dropout(0.25)) # helps prevent overfitting (25% of neurons disconnected randomly)
# (CONV => RELU) * 2 => POOL layer set (increasing number of layers as you go deeper into CNN)
model.add(Conv2D(64, (3, 3), padding="same", input_shape=input_shape)) # 64 3x3 filters
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(Conv2D(64, (3, 3), padding="same", input_shape=input_shape)) # 64 3x3 filters
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(MaxPooling2D(pool_size=(2,2)))
model.add(Dropout(0.25)) # helps prevent overfitting (25% of neurons disconnected randomly)
# (CONV => RELU) * 3 => POOL layer set (input volume size becoming smaller and smaller)
model.add(Conv2D(128, (3, 3), padding="same", input_shape=input_shape)) # 128 3x3 filters
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(Conv2D(128, (3, 3), padding="same", input_shape=input_shape)) # 128 3x3 filters
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(Conv2D(128, (3, 3), padding="same", input_shape=input_shape)) # 128 3x3 filters
model.add(Activation("relu"))
model.add(BatchNormalization(axis=channel_dimension))
model.add(MaxPooling2D(pool_size=(2,2)))
model.add(Dropout(0.25)) # helps prevent overfitting (25% of neurons disconnected randomly)
# only set of FC => RELU layers
model.add(Flatten())
model.add(Dense(512))
model.add(Activation("relu"))
model.add(BatchNormalization())
model.add(Dropout(0.5))
# sigmoid classifier (output layer)
model.add(Dense(classes))
model.add(Activation("sigmoid"))
Is there any glaring omissions or mistakes with this model or can I simply not solve this problem using deep learning (with my current GPU, a GTX 970)?
Thanks for your time and experience,
Josh
EDIT:
Here is my code for compiling/training the model:
# initialise the model and optimiser
print("[INFO] Training network...")
opt = SGD(lr=initial_lr, decay=initial_lr / epochs)
model.compile(loss="sparse_categorical_crossentropy", optimizer=opt, metrics=["accuracy"])
# set up checkpoints
model_name = "output/50_epochs_{epoch:02d}_{val_acc:.2f}.model"
checkpoint = ModelCheckpoint(model_name, monitor='val_acc', verbose=1,
save_best_only=True, mode='max')
reduce_lr = ReduceLROnPlateau(monitor='val_loss', factor=0.2,
patience=5, min_lr=0.001)
tensorboard = TensorBoard(log_dir="logs/{}".format(time()))
callbacks_list = [checkpoint, reduce_lr, tensorboard]
# train the network
H = model.fit_generator(training_set, steps_per_epoch=500, epochs=50, validation_data=test_set, validation_steps=150, callbacks=callbacks_list)

Independently of any other advice (including the answer already provided), and assuming classes=2 (which you don't clarify - there is a reason we ask for a MCVE here), you seem to perform a fundamental mistake in your final layer, i.e.:
# sigmoid classifier (output layer)
model.add(Dense(classes))
model.add(Activation("sigmoid"))
A sigmoid activation is suitable only if your final layer consists of a single node; if classes=2, as I suspect, based also on your puzzling statement in the comments that
with three different images, my results are 0.987 bad and 0.999 good
and
I was giving you the predictions from the model previously
you should use a softmax activation, i.e.
model.add(Dense(classes))
model.add(Activation("softmax"))
Alternatively, you could use sigmoid, but your final layer should consist of a single node, i.e.
model.add(Dense(1))
model.add(Activation("sigmoid"))
The latter is usually preferred in binary classification settings, but the results should be the same in principle.
UPDATE (after updating the question):
sparse_categorical_crossentropy is not the correct loss here, either.
All in all, try the following changes:
model.compile(loss="binary_crossentropy", optimizer=Adam(), metrics=["accuracy"])
# final layer:
model.add(Dense(1))
model.add(Activation("sigmoid"))
with Adam optimizer (needs import). Also, dropout should not be used by default - see this thread; start without it and only add if necessary (i.e. if you see signs of overfitting).

I suggest you go for transfer learning instead of training the whole network.
use the weights trained on a huge Dataset like ImageNet
you can easily do this using Keras you just need to import model with weights like xception and remove last layer which represents 1000 classes of imagenet dataset to 2 node dense layer cause you have only 2 classes and set trainable=False for the base layer and trainable=True for custom added layers like dense layer having node = 2.
and you can train the model as usual way.
Demo code -
from keras.applications import *
from keras.models import Model
base_model = Xception(input_shape=(img_width, img_height, 3), weights='imagenet', include_top=False
x = base_model.output
x = GlobalAveragePooling2D()(x)
predictions = Dense(2, activation='softmax')(x)
model = Model(base_model.input, predictions)
# freezing the base layer weights
for layer in base_model.layers:
layer.trainable = False

Extracting last layers of keras model as a submodel

Say we have a convolutional neural network M. I can extract features from images by using
extractor = Model(M.inputs, M.get_layer('last_conv').output)
features = extractor.predict(X)
How can I get the model that will predict classes using features?
I can't use the following lines because it requires the input of the model to be a placeholder.
predictor = Model([M.get_layer('next_layer').input], M.outputs)
pred = predictor.predict(features)
I also can't use K.function because later I want to use it as part of another model, so I will be appliyng predictor to tf.tensor, not np.array.

This is not the nicest solution, but it works:
from keras.models import Sequential
from keras.layers import Conv2D, MaxPooling2D
from keras.layers import Dense, Dropout, Flatten
def cnn():
model = Sequential()
model.add(Conv2D(32, kernel_size=(3, 3),
activation='relu',
input_shape=(28, 28, 1), name='l_01'))
model.add(Conv2D(64, (3, 3), activation='relu', name='l_02'))
model.add(MaxPooling2D(pool_size=(2, 2), name='l_03'))
model.add(Dropout(0.25, name='l_04'))
model.add(Flatten(name='l_05'))
model.add(Dense(128, activation='relu', name='l_06'))
model.add(Dropout(0.5, name='l_07'))
model.add(Dense(10, activation='softmax', name='l_08'))
return model
def predictor(input_shape):
model = Sequential()
model.add(Flatten(name='l_05', input_shape=(12, 12, 64)))
model.add(Dense(128, activation='relu', name='l_06'))
model.add(Dropout(0.5, name='l_07'))
model.add(Dense(10, activation='softmax', name='l_08'))
return model
cnn_model = cnn()
cnn_model.save('/tmp/cnn_model.h5')
predictor_model = predictor(cnn_model.output.shape)
predictor_model.load_weights('/tmp/cnn_model.h5', by_name=True)

Every layer in the model is indexed. So if you know which layers you need, you could loop through them, copying them into a new model. This operation should copy the weights inside the layer as well.
Here's a model (from Oli Blum's answer):
model = Sequential()
# add some layers
model.add(Conv2D(32, kernel_size=(3, 3),
activation='relu',
input_shape=(28, 28, 1), name='l_01'))
model.add(Conv2D(64, (3, 3), activation='relu', name='l_02'))
model.add(MaxPooling2D(pool_size=(2, 2), name='l_03'))
model.add(Dropout(0.25, name='l_04'))
model.add(Flatten(name='l_05'))
model.add(Dense(128, activation='relu', name='l_06'))
model.add(Dropout(0.5, name='l_07'))
model.add(Dense(10, activation='softmax', name='l_08'))
Say you wanted the last three layers:
def extract_layers(main_model, starting_layer_ix, ending_layer_ix):
# create an empty model
new_model = Sequential()
for ix in range(starting_layer_ix, ending_layer_ix + 1):
curr_layer = main_model.get_layer(index=ix)
# copy this layer over to the new model
new_model.add(curr_layer)
return new_model

It depends on what you want to do.
If you are going to throw away the feature extractor afterwards
If you plan on training the feature extractor later
If you are going to use the extracted features but you don't intend on training the model used to generate them, you could use the predict method to get the features as you did:
features = extractor.predict(X)
then save its output to a file (np.save or cPickle or whatever).
After that you could use that new dataset as the input to a new model.
If you plan on training the feature extractor later you'll need to stack the two networks as seen here with vgg as feature extractor https://github.com/fchollet/keras/issues/4576:
img_width, img_height = 150, 150
vgg16_model = VGG16(include_top=False, weights='imagenet')
input = Input(batch_shape=vgg16_model.output_shape)
x = GlobalAveragePooling2D()(input)
x = Dense(256, activation='relu')(x)
x = Dropout(0.5)(x)
predict = Dense(1, activation='sigmoid')(x)
top_model = Model(input, predict)
top_model.load_weights(os.path.join(data_path, 'VGG16Classifier.hdf5'))
input = Input(shape=(3, img_width, img_height))
x = vgg16_model(input)
predict = top_model(x)
model = Model(input, predict)
PS: This example uses channels first ordering. If you are using tensorflow you should change the shape to shape=(img_width, img_height,3 )