介绍

https://www.youtube.com/watch?v=jajksuQW4mc

https://www.youtube.com/watch?v=2-Ol7ZB0MmU

https://www.youtube.com/watch?v=H3ciJF2eCJI

卷积神经网络---图片识别,视频分析、语音识别

参考谷歌youtube上提供的CNN视频演示

数据组织形式

计算机识别的不是颜色本身,而是由颜色组成的矩阵

  如果是黑色的话,矩阵的维度为2维

  如果是彩色的话,矩阵的维度是3维度,还有一个RGB通道来表示颜色

2.0CNN-LMLPHP

卷积神经网络结构

2.0CNN-LMLPHP2.0CNN-LMLPHP

卷积的图示理解

用一个XYK的长方体矩阵去依次经过原始数据的每一块,这就是简单的卷积操作,也是一种对矩阵的操作

另:stride 表示一次跨几步

2.0CNN-LMLPHP

2.0CNN-LMLPHP

2.0CNN-LMLPHP

不断压缩长和宽,而增加厚度

2.0CNN-LMLPHP

跨度太长的话会丢掉一些信息

所以将跨度设置的小一些,通过pooling变成和上述跨度一样大的形状

一种maxpooling  一种averagepooling

2.0CNN-LMLPHP

如何设计卷积神经网络?

给一张图片image

全连接层就类比于普通神经网络的隐层或隐藏层

2.0CNN-LMLPHP

CNN代码实战MNIST手写体识别数据集

python2和3均可执行

"""
Please note, this code is only for python 3+. If you are using python 2+, please modify the code accordingly.
"""
from __future__ import print_function
import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data
# number 1 to 10 data
mnist = input_data.read_data_sets('MNIST_data', one_hot=True) def compute_accuracy(v_xs, v_ys):
global prediction
y_pre = sess.run(prediction, feed_dict={xs: v_xs, keep_prob: 1})
correct_prediction = tf.equal(tf.argmax(y_pre,1), tf.argmax(v_ys,1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))
result = sess.run(accuracy, feed_dict={xs: v_xs, ys: v_ys, keep_prob: 1})
return result def weight_variable(shape):
initial = tf.truncated_normal(shape, stddev=0.1)
return tf.Variable(initial) def bias_variable(shape):
initial = tf.constant(0.1, shape=shape)
return tf.Variable(initial) def conv2d(x, W):
# stride [1, x_movement, y_movement, 1]
# Must have strides[0] = strides[3] = 1
return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding='SAME') def max_pool_2x2(x):
# stride [1, x_movement, y_movement, 1]
return tf.nn.max_pool(x, ksize=[1,2,2,1], strides=[1,2,2,1], padding='SAME') # define placeholder for inputs to network
xs = tf.placeholder(tf.float32, [None, 784])/255. # 28x28
ys = tf.placeholder(tf.float32, [None, 10])
keep_prob = tf.placeholder(tf.float32)
x_image = tf.reshape(xs, [-1, 28, 28, 1])
# print(x_image.shape) # [n_samples, 28,28,1] ## conv1 layer ##
W_conv1 = weight_variable([5,5, 1,32]) # patch 5x5, in size 1, out size 32
b_conv1 = bias_variable([32])
h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1) # output size 28x28x32
h_pool1 = max_pool_2x2(h_conv1) # output size 14x14x32 ## conv2 layer ##
W_conv2 = weight_variable([5,5, 32, 64]) # patch 5x5, in size 32, out size 64
b_conv2 = bias_variable([64])
h_conv2 = tf.nn.relu(conv2d(h_pool1, W_conv2) + b_conv2) # output size 14x14x64
h_pool2 = max_pool_2x2(h_conv2) # output size 7x7x64 ## fc1 layer ##
W_fc1 = weight_variable([7*7*64, 1024])
b_fc1 = bias_variable([1024])
# [n_samples, 7, 7, 64] ->> [n_samples, 7*7*64]
h_pool2_flat = tf.reshape(h_pool2, [-1, 7*7*64])
h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)
h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob) ## fc2 layer ##
W_fc2 = weight_variable([1024, 10])
b_fc2 = bias_variable([10])
prediction = tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2) # the error between prediction and real data
cross_entropy = tf.reduce_mean(-tf.reduce_sum(ys * tf.log(prediction),
reduction_indices=[1])) # loss
train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy) sess = tf.Session()
# important step
# tf.initialize_all_variables() no long valid from
# 2017-03-02 if using tensorflow >= 0.12
if int((tf.__version__).split('.')[1]) < 12 and int((tf.__version__).split('.')[0]) < 1:
init = tf.initialize_all_variables()
else:
init = tf.global_variables_initializer()
sess.run(init) for i in range(1000):
batch_xs, batch_ys = mnist.train.next_batch(100)
sess.run(train_step, feed_dict={xs: batch_xs, ys: batch_ys, keep_prob: 0.5})
if i % 50 == 0:
print(compute_accuracy(mnist.test.images, mnist.test.labels))

结果显示:经过100步已经可以达到75%了,效果也很明显

2.0CNN-LMLPHP

05-11 09:37