ยป Keras API reference / Layers API / Convolution layers / DepthwiseConv2D layer

DepthwiseConv2D layer

DepthwiseConv2D class

tf.keras.layers.DepthwiseConv2D(
    kernel_size,
    strides=(1, 1),
    padding="valid",
    depth_multiplier=1,
    data_format=None,
    dilation_rate=(1, 1),
    activation=None,
    use_bias=True,
    depthwise_initializer="glorot_uniform",
    bias_initializer="zeros",
    depthwise_regularizer=None,
    bias_regularizer=None,
    activity_regularizer=None,
    depthwise_constraint=None,
    bias_constraint=None,
    **kwargs
)

Depthwise separable 2D convolution.

Depthwise Separable convolutions consist of performing just the first step in a depthwise spatial convolution (which acts on each input channel separately). The depth_multiplier argument controls how many output channels are generated per input channel in the depthwise step.

Arguments

  • 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). "valid" means no padding. "same" results in padding evenly to the left/right or up/down of the input such that output has the same height/width dimension as the input.
  • depth_multiplier: The number of depthwise convolution output channels for each input channel. The total number of depthwise convolution output channels will be equal to filters_in * depth_multiplier.
  • 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. Currently, specifying any dilation_rate value != 1 is incompatible with specifying any strides value != 1.
  • 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.
  • depthwise_initializer: Initializer for the depthwise kernel matrix ( see keras.initializers).
  • bias_initializer: Initializer for the bias vector ( see keras.initializers).
  • depthwise_regularizer: Regularizer function applied to the depthwise kernel 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).
  • depthwise_constraint: Constraint function applied to the depthwise kernel matrix ( see keras.constraints).
  • bias_constraint: Constraint function applied to the bias vector ( see keras.constraints).

Input shape

4D tensor with shape: [batch_size, channels, rows, cols] if data_format='channels_first' or 4D tensor with shape: [batch_size, rows, cols, channels] if data_format='channels_last'.

Output shape

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

Returns

A tensor of rank 4 representing activation(depthwiseconv2d(inputs, kernel) + bias).

Raises

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