add resnet50 example

examples/resnet_50.py

@@ -0,0 +1,216 @@
+'''This script demonstrates how to build a deep residual network
+using the Keras functional API.
+
+get_resne50 returns the deep residual network model (50 layers)
+
+Please visit Kaiming He's GitHub homepage:
+https://github.com/KaimingHe
+for more information.
+
+The related paper is
+"Deep Residual Learning for Image Recognition"
+Kaiming He, Xiangyu Zhang, Shaoqing Ren, Jian Sun
+http://arxiv.org/abs/1512.03385
+
+Pretrained weights were converted from Kaiming He's caffe model directly.
+
+For now we provide weights for the tensorflow backend only,
+thus use 'tf' dim_ordering (e.g. input_shape=(224, 224, 3) for 224*224 color image)
+would accelerate the computation, but we also provide weights for 'th' dim_ordering for compatibility.
+please donwload them at:
+http://pan.baidu.com/s/1o8pO2q2 ('th' dim ordering, For China)
+http://pan.baidu.com/s/1pLanuTt ('tf' dim ordering, For China)
+
+https://drive.google.com/open?id=0B4ChsjFJvew3NVQ2U041Q0xHRHM ('th' dim ordering, For other countries)
+https://drive.google.com/open?id=0B4ChsjFJvew3NWN5THdxcTdSWmc ('tf' dim ordering, For other countries)
+
+@author: BigMoyan, University of Electronic Science and Technology of China
+'''
+from keras.layers import merge
+from keras.layers.convolutional import Convolution2D, MaxPooling2D, ZeroPadding2D, AveragePooling2D
+from keras.layers.core import Dense, Activation, Flatten
+from keras.layers.normalization import BatchNormalization
+from keras.models import Model
+from keras.layers import Input
+from keras.preprocessing.image import load_img, img_to_array
+import keras.backend as K
+import numpy as np
+
+# The names of layers in resnet50 are generated with the following format
+# [type][stage][block]_branch[branch][layer]
+# type: 'res' for conv layer, 'bn' and 'scale' for BN layer
+# stage: from '2' to '5', current stage number
+# block: 'a','b','c'... for different blocks in a stage
+# branch: '1' for shortcut and '2' for main path
+# layer: 'a','b','c'... for different layers in a block
+
+def identity_block(input_tensor, kernel_size, filters, stage, block):
+    """
+    the identity_block is the block that has no conv layer at shortcut
+    params:
+        input_tensor: input tensor
+        kernel_size: defualt 3, the kernel size of middle conv layer at main path
+        filters: list of integers, the nb_filters of 3 conv layer at main path
+        stage: integer, current stage label, used for generating layer names
+        block: 'a','b'..., current block label, used for generating layer names
+    """
+    dim_ordering = K.image_dim_ordering()
+    nb_filter1, nb_filter2, nb_filter3 = filters
+    if dim_ordering == 'tf':
+        axis = 3
+    else:
+        axis = 1
+    conv_name_base = 'res' + str(stage) + block + '_branch'
+    bn_name_base = 'bn' + str(stage) + block + '_branch'
+
+    out = Convolution2D(nb_filter1, 1, 1, dim_ordering=dim_ordering, name=conv_name_base + '2a')(input_tensor)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2a')(out)
+    out = Activation('relu')(out)
+
+    out = out = Convolution2D(nb_filter2, kernel_size, kernel_size, border_mode='same',
+                              dim_ordering=dim_ordering, name=conv_name_base + '2b')(out)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2b')(out)
+    out = Activation('relu')(out)
+
+    out = Convolution2D(nb_filter3, 1, 1, dim_ordering=dim_ordering, name=conv_name_base + '2c')(out)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2c')(out)
+
+    out = merge([out, input_tensor], mode='sum')
+    out = Activation('relu')(out)
+    return out
+
+
+def conv_block(input_tensor, kernel_size, filters, stage, block, strides=(2, 2)):
+    """
+    conv_block is the block that has a conv layer at shortcut
+    params:
+        input_tensor: input tensor
+        kernel_size: defualt 3, the kernel size of middle conv layer at main path
+        filters: list of integers, the nb_filters of 3 conv layer at main path
+        stage: integer, current stage label, used for generating layer names
+        block: 'a','b'..., current block label, used for generating layer names
+
+    Note that from stage 3, the first conv layer at main path is with subsample=(2,2)
+    And the shortcut should has subsample=(2,2) as well
+    """
+    nb_filter1, nb_filter2, nb_filter3 = filters
+    dim_ordering = K.image_dim_ordering()
+    if dim_ordering == 'tf':
+        axis = 3
+    else:
+        axis = 1
+    conv_name_base = 'res' + str(stage) + block + '_branch'
+    bn_name_base = 'bn' + str(stage) + block + '_branch'
+
+    out = Convolution2D(nb_filter1, 1, 1, subsample=strides,
+                        dim_ordering=dim_ordering, name=conv_name_base + '2a')(input_tensor)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2a')(out)
+    out = Activation('relu')(out)
+
+    out = Convolution2D(nb_filter2, kernel_size, kernel_size, border_mode='same',
+                        dim_ordering=dim_ordering, name=conv_name_base + '2b')(out)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2b')(out)
+    out = Activation('relu')(out)
+
+    out = Convolution2D(nb_filter3, 1, 1, dim_ordering=dim_ordering, name=conv_name_base + '2c')(out)
+    out = BatchNormalization(axis=axis, name=bn_name_base + '2c')(out)
+
+    shortcut = Convolution2D(nb_filter3, 1, 1, subsample=strides,
+                             dim_ordering=dim_ordering, name=conv_name_base + '1')(input_tensor)
+    shortcut = BatchNormalization(axis=axis, name=bn_name_base + '1')(shortcut)
+
+    out = merge([out, shortcut], mode='sum')
+    out = Activation('relu')(out)
+    return out
+
+
+def read_img(img_path):
+    """
+    this function returns preprocessed image
+    """
+    dim_ordering = K.image_dim_ordering()
+    mean = (103.939, 116.779, 123.68)
+    img = load_img(img_path, target_size=(224, 224))
+    img = img_to_array(img, dim_ordering=dim_ordering)
+
+    # decenterize
+    img[0, :, :] -= mean[0]
+    img[1, :, :] -= mean[1]
+    img[2, :, :] -= mean[2]
+
+    # 'RGB'->'BGR'
+    if dim_ordering == 'th':
+        img = img[::-1, :, :]
+    else:
+        img = img[:, :, ::-1]
+
+    # expand dim for test
+    img = np.expand_dims(img, axis=0)
+    return img
+
+
+def get_resnet50():
+    """
+    this function returns the 50-layer residual network model
+    you should load pretrained weights if you want to use it directly.
+    Note that since the pretrained weights is converted from caffemodel
+    the order of channels for input image should be 'BGR' (the channel order of caffe)
+    """
+    if K.image_dim_ordering() == 'tf':
+        inp = Input(shape=(224, 224, 3))
+        axis = 3
+    else:
+        inp = Input(shape=(3, 224, 224))
+        axis = 1
+
+    dim_ordering = K.image_dim_ordering()
+    out = ZeroPadding2D((3, 3), dim_ordering=dim_ordering)(inp)
+    out = Convolution2D(64, 7, 7, subsample=(2, 2), dim_ordering=dim_ordering, name='conv1')(out)
+    out = BatchNormalization(axis=axis, name='bn_conv1')(out)
+    out = Activation('relu')(out)
+    out = MaxPooling2D((3, 3), strides=(2, 2), dim_ordering=dim_ordering)(out)
+
+    out = conv_block(out, 3, [64, 64, 256], stage=2, block='a', strides=(1, 1))
+    out = identity_block(out, 3, [64, 64, 256], stage=2, block='b')
+    out = identity_block(out, 3, [64, 64, 256], stage=2, block='c')
+
+    out = conv_block(out, 3, [128, 128, 512], stage=3, block='a')
+    out = identity_block(out, 3, [128, 128, 512], stage=3, block='b')
+    out = identity_block(out, 3, [128, 128, 512], stage=3, block='c')
+    out = identity_block(out, 3, [128, 128, 512], stage=3, block='d')
+
+    out = conv_block(out, 3, [256, 256, 1024], stage=4, block='a')
+    out = identity_block(out, 3, [256, 256, 1024], stage=4, block='b')
+    out = identity_block(out, 3, [256, 256, 1024], stage=4, block='c')
+    out = identity_block(out, 3, [256, 256, 1024], stage=4, block='d')
+    out = identity_block(out, 3, [256, 256, 1024], stage=4, block='e')
+    out = identity_block(out, 3, [256, 256, 1024], stage=4, block='f')
+
+    out = conv_block(out, 3, [512, 512, 2048], stage=5, block='a')
+    out = identity_block(out, 3, [512, 512, 2048], stage=5, block='b')
+    out = identity_block(out, 3, [512, 512, 2048], stage=5, block='c')
+
+    out = AveragePooling2D((7, 7), dim_ordering=dim_ordering)(out)
+    out = Flatten()(out)
+    out = Dense(1000, activation='softmax', name='fc1000')(out)
+
+    model = Model(inp, out)
+
+    return model
+
+
+if __name__ == '__main__':
+    K.set_image_dim_ordering('tf')
+    weights_file = K.image_dim_ordering() + '_dim_ordering_resnet50.h5'
+    resnet_model = get_resnet50()
+    resnet_model.load_weights(weights_file)
+    test_img1 = read_img('cat.jpg')
+    test_img2 = read_img('airplane.jpg')
+    # you may download synset_words from address given at the begining of this file
+    class_table = open('synset_words', 'r')
+    lines = class_table.readlines()
+    print "result for test 1 is"
+    print lines[np.argmax(resnet_model.predict(test_img1)[0])]
+    print "result for test 2 is"
+    print lines[np.argmax(resnet_model.predict(test_img2)[0])]
+    class_table.close()