Neural Style Tranfer¶
Neural Style Transfer is stylizing an image in style of another image.
Here we try to implement two methods of Neural Style Transfer namely - Optimization-based Neural Style Transfer and Fast Neural Style Transfer.
Aplications of Neural Style Transfer
- Creating excellent artistic looking images using different style images.
- Can be used for Image Data augmentation purposes.
- Websites like DeepArt and Prisma use Neural Style Transfer to create artistic images.
In [1]:
!wget https://cainvas-static.s3.amazonaws.com/media/user_data/Yuvnish17/neural_style_transfer_data.zip
!unzip -qo neural_style_transfer_data.zip
Importing Libraries
In [2]:
import matplotlib.pyplot as plt
import cv2
import tensorflow as tf
import numpy as np
from tensorflow import keras
from tensorflow.keras.applications import vgg16
from tensorflow import keras
from tensorflow.keras import backend as K
from tensorflow.keras.regularizers import Regularizer
from tensorflow.keras.layers import Input
from tensorflow.keras.layers import concatenate
from tensorflow.keras.models import Model,Sequential
from tensorflow.keras.optimizers import Adam
from tensorflow.keras.preprocessing.image import ImageDataGenerator
from neural_style_transfer_data.layers import InputNormalize,VGGNormalize,ReflectionPadding2D,Denormalize,conv_bn_relu,res_conv,dconv_bn_nolinear
import time
Optimization-based Neural Style Transfer¶
Loading the Input Image and the Style Image
In [3]:
img = cv2.imread('neural_style_transfer_data/content.png')
print(img.shape)
(height, width, channels) = img.shape
img_rows = 400
img_cols = int(width * img_rows / height)
result_prefix = "neural_style_transfer_generated"
# Weights of the different loss components
total_variation_weight = 1e-6
style_weight = 5e-6
content_weight = 1e-8
Visualizing the The Style Image and the Input Image
In [4]:
figure = plt.figure(figsize=(10, 10))
style_img = cv2.imread('neural_style_transfer_data/style_image3.jpg')
style_img = cv2.cvtColor(style_img, cv2.COLOR_BGR2RGB)
plt.imshow(style_img)
plt.axis('off')
plt.title('Style Image')
figure2 = plt.figure(figsize=(10, 10))
content_img = cv2.imread('neural_style_transfer_data/content.png')
content_img = cv2.cvtColor(content_img, cv2.COLOR_BGR2RGB)
plt.imshow(content_img)
plt.axis('off')
plt.title('Content Image')
Out[4]:
Defining functions for Preprocessing and Deprocessing images
In [5]:
def preprocess_image(image_path):
image = cv2.imread(image_path)
image = cv2.resize(image, (img_cols, img_rows))
image = np.array(image)
image = np.expand_dims(image, axis=0)
image = vgg16.preprocess_input(image)
return image
def deprocess_image(x):
# Util function to convert a tensor into a valid image
x = x.reshape((img_rows, img_cols, 3))
# Remove zero-center by mean pixel
x[:, :, 0] += 103.939
x[:, :, 1] += 116.779
x[:, :, 2] += 123.68
# 'BGR'->'RGB'
x = x[:, :, ::-1]
x = np.clip(x, 0, 255).astype("uint8")
return x
Defining various loss functions and helper functions
In [6]:
def gram_matrix(x):
x = tf.transpose(x, (2, 0, 1))
features = tf.reshape(x, (tf.shape(x)[0], -1))
gram = tf.matmul(features, tf.transpose(features))
return gram
In [7]:
def style_loss(style, combination):
S = gram_matrix(style)
C = gram_matrix(combination)
channels = 3
size = img_rows * img_cols
return tf.reduce_sum(tf.square(S - C)) / (channels * (3 ** 2) * (size ** 2))
In [8]:
def content_loss(base, combination):
return tf.reduce_sum(tf.square(combination - base))
In [9]:
def total_variation_loss(x):
a = tf.square(x[:, : img_rows - 1, : img_cols - 1, :] - x[:, 1:, : img_cols - 1, :])
b = tf.square(x[:, : img_rows - 1, : img_cols - 1, :] - x[:, : img_rows - 1, 1:, :])
return tf.reduce_sum(tf.pow(a + b, 1.25))
Loading the VGG16 model and printing Model Architecture
In [10]:
# Build a VGG19 model loaded with pre-trained ImageNet weights
model = vgg16.VGG16(weights="imagenet", include_top=False)
# Get the symbolic outputs of each "key" layer (we gave them unique names).
outputs_dict = dict([(layer.name, layer.output) for layer in model.layers])
# Set up a model that returns the activation values for every layer in
# VGG19 (as a dict).
feature_extractor = keras.Model(inputs=model.inputs, outputs=outputs_dict)
In [11]:
feature_extractor.summary()
Defining the Feature Extraction layers and the Total Loss function of the model
In [12]:
style_layer_names = [
"block1_conv1",
"block2_conv1",
"block3_conv1",
"block4_conv1",
"block5_conv1",
]
# The layer to use for the content loss.
content_layer_name = "block5_conv2"
def compute_loss(combination_image, base_image, style_reference_image):
input_tensor = tf.concat(
[base_image, style_reference_image, combination_image], axis=0
)
features = feature_extractor(input_tensor)
# Initialize the loss
loss = tf.zeros(shape=())
# Add content loss
layer_features = features[content_layer_name]
base_image_features = layer_features[0, :, :, :]
combination_features = layer_features[2, :, :, :]
loss = loss + content_weight * content_loss(
base_image_features, combination_features
)
# Add style loss
for layer_name in style_layer_names:
layer_features = features[layer_name]
style_reference_features = layer_features[1, :, :, :]
combination_features = layer_features[2, :, :, :]
sl = style_loss(style_reference_features, combination_features)
loss += (style_weight / len(style_layer_names)) * sl
# Add total variation loss
loss += total_variation_weight * total_variation_loss(combination_image)
return loss
In [13]:
@tf.function
def compute_loss_and_grads(combination_image, base_image, style_reference_image):
with tf.GradientTape() as tape:
loss = compute_loss(combination_image, base_image, style_reference_image)
grads = tape.gradient(loss, combination_image)
return loss, grads
Computing the Losses and Transforming the Combination Image
In [14]:
# optimizer = keras.optimizers.Adam(
# keras.optimizers.schedules.ExponentialDecay(
# initial_learning_rate=1000.0, decay_steps=1000, decay_rate=0.96
# )
# )
optimizer = keras.optimizers.SGD(
keras.optimizers.schedules.ExponentialDecay(
initial_learning_rate=100.0, decay_steps=500, decay_rate=0.96
)
)
base_image = preprocess_image('neural_style_transfer_data/content.png')
style_reference_image = preprocess_image('neural_style_transfer_data/style_image3.jpg')
combination_image = tf.Variable(preprocess_image('neural_style_transfer_data/content.png'))
print(base_image.shape)
print(style_reference_image.shape)
print(combination_image.shape)
losses = []
iter = []
# combination_image = tf.Variable(content_img)
iterations = 8000
for i in range(1, iterations + 1):
loss, grads = compute_loss_and_grads(
combination_image, base_image, style_reference_image
)
optimizer.apply_gradients([(grads, combination_image)])
losses.append(loss)
iter.append(i)
if i % 100 == 0:
print("Iteration %d: loss=%.2f" % (i, loss))
if i == 8000:
img = deprocess_image(combination_image.numpy())
fname = result_prefix + "_at_iteration_%d.png" % i
# keras.preprocessing.image.save_img(fname, img)
cv2.imwrite(fname, img)
Visualizing the Result
In [15]:
figure2 = plt.figure(figsize=(10, 10))
content_img = cv2.imread('neural_style_transfer_generated_at_iteration_8000.png')
content_img = cv2.cvtColor(content_img, cv2.COLOR_BGR2RGB)
plt.imshow(content_img)
plt.axis('off')
plt.title('Content Image')
Out[15]:
Loss vs Number of Iterations Plot starting (values are plotted after the 100th iteration)
In [16]:
iter = [i for i in range(100, 8001)]
figure = plt.figure(figsize=(10, 10))
plt.plot(iter, losses[99:])
plt.xlabel('number of iterations')
plt.ylabel('loss value')
plt.title('Loss vs Number of Iterations plot')
plt.show()
Fast Neural Style Transfer¶
Defining the various helper functions, loss functions and model architecture functions using Keras and Tensorflow for model architecture visualization
In [14]:
def preprocess_image(image_path, image_width, image_height):
image = cv2.imread(image_path)
image = cv2.resize(image, (image_width, image_height))
image = np.array(image)
image = np.expand_dims(image, axis=0)
# image = vgg16.preprocess_input(image)
return image
def deprocess_image(x):
# Util function to convert a tensor into a valid image
x = x.reshape((img_rows, img_cols, 3))
# Remove zero-center by mean pixel
x[:, :, 0] += 103.939
x[:, :, 1] += 116.779
x[:, :, 2] += 123.68
# 'BGR'->'RGB'
x = x[:, :, ::-1]
x = np.clip(x, 0, 255).astype("uint8")
return x
In [15]:
dummy_loss_value = K.variable(0.0)
def dummy_loss(y_true, y_pred):
return dummy_loss_value
In [16]:
@tf.function
def compute_loss_and_grads(y_true, y_pred):
with tf.GradientTape() as tape:
loss = dummy_loss(y_true, y_pred)
grads = tape.gradient(loss, y_pred)
return loss, grads
In [17]:
def gram_matrix(x):
x = tf.transpose(x, (2, 0, 1))
features = tf.reshape(x, (tf.shape(x)[0], -1))
gram = tf.matmul(features, tf.transpose(features))
return gram
In [18]:
class StyleReconstructionRegularizer(Regularizer):
""" Johnson et al 2015 https://arxiv.org/abs/1603.08155 """
def __init__(self, style_feature_target, weight=1.0):
self.style_feature_target = style_feature_target
self.weight = weight
self.uses_learning_phase = False
super(StyleReconstructionRegularizer, self).__init__()
self.style_gram = gram_matrix(style_feature_target)
def __call__(self, x):
output = x.output[0] # Generated by network
loss = self.weight * K.sum(K.mean(K.square((self.style_gram-gram_matrix(output) ))))
return loss
class FeatureReconstructionRegularizer(Regularizer):
""" Johnson et al 2015 https://arxiv.org/abs/1603.08155 """
def __init__(self, weight=1.0):
self.weight = weight
self.uses_learning_phase = False
super(FeatureReconstructionRegularizer, self).__init__()
def __call__(self, x):
generated = x.output[0] # Generated by network features
content = x.output[1] # True X input features
loss = self.weight * K.sum(K.mean(K.square(content-generated)))
return loss
class TVRegularizer(Regularizer):
""" Enforces smoothness in image output. """
def __init__(self, weight=1.0):
self.weight = weight
self.uses_learning_phase = False
super(TVRegularizer, self).__init__()
def __call__(self, x):
assert K.ndim(x.output) == 4
x_out = x.output
shape = K.shape(x_out)
img_width, img_height,channel = (shape[1],shape[2], shape[3])
size = img_width * img_height * channel
if K.image_data_format() == 'th':
a = K.square(x_out[:, :, :img_width - 1, :img_height - 1] - x_out[:, :, 1:, :img_height - 1])
b = K.square(x_out[:, :, :img_width - 1, :img_height - 1] - x_out[:, :, :img_width - 1, 1:])
else:
a = K.square(x_out[:, :img_width - 1, :img_height - 1, :] - x_out[:, 1:, :img_height - 1, :])
b = K.square(x_out[:, :img_width - 1, :img_height - 1, :] - x_out[:, :img_width - 1, 1:, :])
loss = self.weight * K.sum(K.pow(a + b, 1.25))
return loss
In [19]:
def image_transform_net(img_width,img_height,tv_weight=1):
x = Input(shape=(img_width,img_height,3))
a = InputNormalize()(x)
a = ReflectionPadding2D(padding=(40,40),input_shape=(img_width,img_height,3))(a)
a = conv_bn_relu(32, 9, 9, stride=(1,1))(a)
a = conv_bn_relu(64, 9, 9, stride=(2,2))(a)
a = conv_bn_relu(128, 3, 3, stride=(2,2))(a)
for i in range(5):
a = res_conv(128,3,3)(a)
a = dconv_bn_nolinear(64,3,3)(a)
a = dconv_bn_nolinear(32,3,3)(a)
a = dconv_bn_nolinear(3,9,9,stride=(1,1),activation="tanh")(a)
# Scale output to range [0, 255] via custom Denormalize layer
y = Denormalize(name='transform_output')(a)
model = Model(inputs=x, outputs=y)
if tv_weight > 0:
add_total_variation_loss(model.layers[-1],tv_weight)
# add_total_variation_loss(y, tv_weight)
return model, x, y
# return x, y
In [20]:
def loss_net(x_in, trux_x_in,width, height,style_image_path,content_weight,style_weight):
# Append the initial input to the FastNet input to the VGG inputs
x = concatenate([x_in, trux_x_in], axis=0)
# Normalize the inputs via custom VGG Normalization layer
x = VGGNormalize(name="vgg_normalize")(x)
vgg = vgg16.VGG16(include_top=False, weights=None, input_tensor=x)
vgg.load_weights('neural_style_transfer_data/vgg16_weights_tf_dim_ordering_tf_kernels_notop.h5', by_name=True)
vgg.summary()
vgg_output_dict = dict([(layer.name, layer.output) for layer in vgg.layers[-18:]])
vgg_layers = dict([(layer.name, layer) for layer in vgg.layers[-18:]])
if style_weight > 0:
add_style_loss(vgg,style_image_path , vgg_layers, vgg_output_dict, width, height,style_weight)
if content_weight > 0:
add_content_loss(vgg_layers,vgg_output_dict,content_weight)
# Freeze all VGG layers
for layer in vgg.layers[-19:]:
layer.trainable = False
return vgg
In [21]:
def add_style_loss(vgg,style_image_path,vgg_layers,vgg_output_dict,img_width, img_height,weight):
style_img = preprocess_image(style_image_path, img_width, img_height)
print('Getting style features from VGG network.')
style_layers = ['block1_conv2', 'block2_conv2', 'block3_conv3', 'block4_conv3']
style_layer_outputs = []
for layer in style_layers:
style_layer_outputs.append(vgg_output_dict[layer])
print(style_layer_outputs)
print(vgg.layers[-20].input)
vgg_style_func = K.function([vgg.input], style_layer_outputs)
style_features = vgg_style_func([style_img])
# Style Reconstruction Loss
for i, layer_name in enumerate(style_layers):
layer = vgg_layers[layer_name]
feature_var = K.variable(value=style_features[i][0])
style_loss = StyleReconstructionRegularizer(
style_feature_target=feature_var,
weight=weight)(layer)
layer.add_loss(style_loss)
In [22]:
def add_content_loss(vgg_layers,vgg_output_dict,weight):
# Feature Reconstruction Loss
content_layer = 'block3_conv3'
content_layer_output = vgg_output_dict[content_layer]
layer = vgg_layers[content_layer]
content_regularizer = FeatureReconstructionRegularizer(weight)(layer)
layer.add_loss(content_regularizer)
In [23]:
def add_total_variation_loss(transform_output_layer,weight):
# Total Variation Regularization
layer = transform_output_layer # Output layer
tv_regularizer = TVRegularizer(weight)(layer)
layer.add_loss(tv_regularizer)
Keras version of Model Architecture used in Original Fast Neural Style Transfer technique
In [24]:
style_weight = 4.0
content_weight = 1.0
tv_weight = 1e-6
img_width = img_height = 64
style_image_path = 'neural_style_transfer_data/style_image2.jpg'
net, input_itn, output_itn = image_transform_net(img_width, img_height, tv_weight)
# x = Input(shape=(img_width, img_height, 3))
model = loss_net(output_itn, input_itn, img_width, img_height, style_image_path, content_weight, style_weight)
Using Pre-Trained PyTroch models for the Udnie Style Image for stylizing the Input Image
In [25]:
model = cv2.dnn.readNetFromTorch('neural_style_transfer_data/udnie.t7')
image = cv2.imread('neural_style_transfer_data/content.png')
(h, w) = image.shape[:2]
image = cv2.resize(image, (600, h))
(h, w, c) = image.shape
print(h, w, c)
In [26]:
blob = cv2.dnn.blobFromImage(image, 1.0, (w, h), (103.939, 116.779, 123.680), swapRB=False, crop=False)
model.setInput(blob)
output = model.forward()
output = output.reshape((3, output.shape[2], output.shape[3]))
output[0] += 103.939
output[1] += 116.779
output[2] += 123.680
output /= 255.0
output = output.transpose(1, 2, 0)
In [27]:
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
figure = plt.figure(figsize=(10, 10))
plt.imshow(image)
plt.axis('off')
figure2 = plt.figure(figsize=(10, 10))
plt.imshow(output)
plt.axis('off')
Out[27]:
In [ ]: