tf.keras.layers.Conv2D

TensorFlow 1 version View source on GitHub

2D convolution layer (e.g. spatial convolution over images).

tf.keras.layers.Conv2D(
    filters, kernel_size, strides=(1, 1), padding='valid', data_format=None,
    dilation_rate=(1, 1), groups=1, activation=None, use_bias=True,
    kernel_initializer='glorot_uniform', bias_initializer='zeros',
    kernel_regularizer=None, bias_regularizer=None, activity_regularizer=None,
    kernel_constraint=None, bias_constraint=None, **kwargs
)

This layer creates a convolution kernel that is convolved with the layer input to produce a tensor of outputs. If use_bias is True, a bias vector is created and added to the outputs. Finally, if activation is not None, it is applied to the outputs as well.

When using this layer as the first layer in a model, provide the keyword argument input_shape (tuple of integers, does not include the sample axis), e.g. input_shape=(128, 128, 3) for 128x128 RGB pictures in data_format="channels_last".

Examples:

# The inputs are 28x28 RGB images with `channels_last` and the batch
# size is 4.
input_shape = (4, 28, 28, 3)
x = tf.random.normal(input_shape)
y = tf.keras.layers.Conv2D(
2, 3, activation='relu', input_shape=input_shape[1:])(x)
print(y.shape)
(4, 26, 26, 2)
 
# With `dilation_rate` as 2.
input_shape = (4, 28, 28, 3)
x = tf.random.normal(input_shape)
y = tf.keras.layers.Conv2D(
2, 3, activation='relu', dilation_rate=2, input_shape=input_shape[1:])(x)
print(y.shape)
(4, 24, 24, 2)
 
# With `padding` as "same".
input_shape = (4, 28, 28, 3)
x = tf.random.normal(input_shape)
y = tf.keras.layers.Conv2D(
2, 3, activation='relu', padding="same", input_shape=input_shape[1:])(x)
print(y.shape)
(4, 28, 28, 2)
 
# With extended batch shape [4, 7]:
input_shape = (4, 7, 28, 28, 3)
x = tf.random.normal(input_shape)
y = tf.keras.layers.Conv2D(
2, 3, activation='relu', input_shape=input_shape[2:])(x)
print(y.shape)
(4, 7, 26, 26, 2)

filters Integer, the dimensionality of the output space (i.e. the number of output filters in the convolution).
kernel_size An integer or tuple/list of 2 integers, specifying the height and width of the 2D convolution window. Can be a single integer to specify the same value for all spatial dimensions.
strides An integer or tuple/list of 2 integers, specifying the strides of the convolution along the height and width. Can be a single integer to specify the same value for all spatial dimensions. Specifying any stride value != 1 is incompatible with specifying any dilation_rate value != 1.
padding one of "valid" or "same" (case-insensitive).
data_format A string, one of channels_last (default) or channels_first. The ordering of the dimensions in the inputs. channels_last corresponds to inputs with shape (batch_size, height, width, channels) while channels_first corresponds to inputs with shape (batch_size, channels, height, width). It defaults to the image_data_format value found in your Keras config file at ~/.keras/keras.json. If you never set it, then it will be channels_last.
dilation_rate an integer or tuple/list of 2 integers, specifying the dilation rate to use for dilated convolution. Can be a single integer to specify the same value for all spatial dimensions. Currently, specifying any dilation_rate value != 1 is incompatible with specifying any stride value != 1.
groups A positive integer specifying the number of groups in which the input is split along the channel axis. Each group is convolved separately with filters / groups filters. The output is the concatenation of all the groups results along the channel axis. Input channels and filters must both be divisible by groups.
activation Activation function to use. If you don't specify anything, no activation is applied (see keras.activations).
use_bias Boolean, whether the layer uses a bias vector.
kernel_initializer Initializer for the kernel weights matrix (see keras.initializers).
bias_initializer Initializer for the bias vector (see keras.initializers).
kernel_regularizer Regularizer function applied to the kernel weights matrix (see keras.regularizers).
bias_regularizer Regularizer function applied to the bias vector (see keras.regularizers).
activity_regularizer Regularizer function applied to the output of the layer (its "activation") (see keras.regularizers).
kernel_constraint Constraint function applied to the kernel matrix (see keras.constraints).
bias_constraint Constraint function applied to the bias vector (see keras.constraints).

Input shape:

4+D tensor with shape: batch_shape + (channels, rows, cols) if data_format='channels_first' or 4+D tensor with shape: batch_shape + (rows, cols, channels) if data_format='channels_last'.

Output shape:

4+D tensor with shape: batch_shape + (filters, new_rows, new_cols) if data_format='channels_first' or 4+D tensor with shape: batch_shape + (new_rows, new_cols, filters) if data_format='channels_last'. rows and cols values might have changed due to padding.

A tensor of rank 4+ representing activation(conv2d(inputs, kernel) + bias).

ValueError if padding is "causal".
ValueError when both strides > 1 and dilation_rate > 1.