#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import division
from __future__ import print_function
import numpy as np
from NumPyNet.utils import check_is_fitted
from NumPyNet.layers.base import BaseLayer
__author__ = ['Mattia Ceccarelli', 'Nico Curti']
__email__ = ['mattia.ceccarelli3@studio.unibo.it', 'nico.curti2@unibo.it']
[docs]class L2Norm_layer(BaseLayer):
'''
L2Norm layer
Parameters
----------
input_shape : tuple (default=None)
Shape of the input in the format (batch, w, h, c), None is used when the layer is part of a Network model.
axis : integer, default None.
Axis along which the L1Normalization is performed. If None, normalize the entire array.
Example
-------
>>> import os
>>>
>>> import pylab as plt
>>> from PIL import Image
>>>
>>> img_2_float = lambda im : ((im - im.min()) * (1./(im.max() - im.min()) * 1.)).astype(float)
>>> float_2_img = lambda im : ((im - im.min()) * (1./(im.max() - im.min()) * 255.)).astype(np.uint8)
>>>
>>> filename = os.path.join(os.path.dirname(__file__), '..', '..', 'data', 'dog.jpg')
>>> inpt = np.asarray(Image.open(filename), dtype=float)
>>> inpt.setflags(write=1)
>>> inpt = img_2_float(inpt)
>>>
>>> # add batch = 1
>>> inpt = np.expand_dims(inpt, axis=0)
>>>
>>> layer = L2Norm_layer(input_shape=inpt.shape)
>>>
>>> # FORWARD
>>> layer.forward(inpt)
>>> forward_out = layer.output
>>> print(layer)
>>>
>>> # BACKWARD
>>>
>>> delta = np.zeros(shape=inpt.shape, dtype=float)
>>> layer.backward(delta)
>>>
>>> # Visualizations
>>>
>>> fig, (ax1, ax2, ax3) = plt.subplots(nrows=1, ncols=3, figsize=(10, 5))
>>> fig.subplots_adjust(left=0.1, right=0.95, top=0.95, bottom=0.15)
>>>
>>> fig.suptitle('L2Normalization Layer')
>>>
>>> ax1.imshow(float_2_img(inpt[0]))
>>> ax1.set_title('Original image')
>>> ax1.axis('off')
>>>
>>> ax2.imshow(float_2_img(forward_out[0]))
>>> ax2.set_title("Forward")
>>> ax2.axis("off")
>>>
>>> ax3.imshow(float_2_img(delta[0]))
>>> ax3.set_title('Backward')
>>> ax3.axis('off')
>>>
>>> fig.tight_layout()
>>> plt.show()
Reference
---------
TODO
'''
def __init__(self, input_shape=None, axis=None, **kwargs):
self.axis = axis
self.scales = None
super(L2Norm_layer, self).__init__(input_shape=input_shape)
def __str__(self):
batch, w, h, c = self.out_shape
return 'l2norm {0:>4d} x{1:>4d} x{2:>4d} x{3:>4d} -> {0:>4d} x{1:>4d} x{2:>4d} x{3:>4d}'.format(
batch, w, h, c)
[docs] def forward(self, inpt):
'''
Forward of the l2norm layer, apply the l2 normalization over
the input along the given axis
Parameters
----------
inpt : array-like
Input batch of images in format (batch, in_w, in_h, in _c)
Returns
-------
self
'''
self._check_dims(shape=self.input_shape, arr=inpt, func='Forward')
norm = (inpt * inpt).sum(axis=self.axis, keepdims=True)
norm = 1. / np.sqrt(norm + 1e-8)
self.output = inpt * norm
self.scales = (1. - self.output) * norm
self.delta = np.zeros(shape=self.out_shape, dtype=float)
return self
[docs] def backward(self, delta):
'''
Backward function of the l2norm layer
Parameters
---------
delta : array-like
delta array of shape (batch, w, h, c). Global delta to be backpropagated.
Returns
-------
self
'''
check_is_fitted(self, 'delta')
self._check_dims(shape=self.input_shape, arr=delta, func='Backward')
self.delta += self.scales
delta[:] += self.delta
return self
if __name__ == '__main__':
import os
import pylab as plt
from PIL import Image
img_2_float = lambda im : ((im - im.min()) * (1./(im.max() - im.min()) * 1.)).astype(float)
float_2_img = lambda im : ((im - im.min()) * (1./(im.max() - im.min()) * 255.)).astype(np.uint8)
filename = os.path.join(os.path.dirname(__file__), '..', '..', 'data', 'dog.jpg')
inpt = np.asarray(Image.open(filename), dtype=float)
inpt.setflags(write=1)
inpt = img_2_float(inpt)
# add batch = 1
inpt = np.expand_dims(inpt, axis=0)
layer = L2Norm_layer(input_shape=inpt.shape)
# FORWARD
layer.forward(inpt)
forward_out = layer.output
print(layer)
# BACKWARD
delta = np.zeros(shape=inpt.shape, dtype=float)
layer.backward(delta)
# Visualizations
fig, (ax1, ax2, ax3) = plt.subplots(nrows=1, ncols=3, figsize=(10, 5))
fig.subplots_adjust(left=0.1, right=0.95, top=0.95, bottom=0.15)
fig.suptitle('L2Normalization Layer')
ax1.imshow(float_2_img(inpt[0]))
ax1.set_title('Original image')
ax1.axis('off')
ax2.imshow(float_2_img(forward_out[0]))
ax2.set_title("Forward")
ax2.axis("off")
ax3.imshow(float_2_img(delta[0]))
ax3.set_title('Backward')
ax3.axis('off')
fig.tight_layout()
plt.show()