crop2dLayer

2-D crop layer

Description

A 2-D crop layer applies 2-D cropping to the input.

There are two inputs to this layer:

• 'in' — The feature map that will be cropped

• 'ref' — A reference layer used to determine the size, [height width], of the cropped output

Once you create this layer, you can add it to a dlnetwork object to make serial connections between layers. To connect the crop layer to other layers, use connectLayers and specify the input names.

Creation

Syntax

layer = crop2dLayer(Mode)

layer = crop2dLayer(Location)

layer = crop2dLayer(___,'Name',Name)

Description

layer = crop2dLayer(Mode) returns a layer that crops an input feature map, and sets the Mode property.

layer = crop2dLayer(Location) returns a layer that crops an input feature map using a rectangular window, and sets the Location property that indicates the position of the window.

layer = crop2dLayer(___,'Name',Name) creates a layer for cropping and sets the optional Name property.

Properties

Mode — Cropping mode

'centercrop' (default) | 'custom'

Cropping mode, specified as 'centercrop' or 'custom'.

Mode	Description
'centercrop'	The location of the cropping window is the center of the input feature map.
'custom'	The location of the cropping window is based on the Location property. This value is automatically set when the Location property is specified as a 2-element row vector.

Data Types: char

Location — Cropping window location

'auto' (default) | 2-element row vector

Cropping window location, specified as 'auto' or a 2-element row vector.

Location	Description
2-element row vector in the format [x y]	The upper-left corner of the cropping window is at the location [x y] of the input feature map. x indicates the location in the horizontal direction and y is the vertical direction.
'auto'	The cropping window is located at the center of the input feature map. This value is automatically set when the Mode property is specified as 'centercrop'.

Name — Layer name

'' (default) | character vector

Layer name, specified as a character vector. For Layer array input, the trainnet and dlnetwork functions automatically assign names to unnamed layers.

Data Types: char

NumInputs — Number of inputs

2 (default)

Number of inputs of the layer. This layer has two inputs.

Data Types: double

InputNames — Input names

{'in' 'ref'} (default)

Input names of the layer. This layer has two inputs, named 'in' and 'ref'.

Data Types: cell

NumOutputs — Number of outputs

Read-only: 1 (default)

This property is read-only.

Number of outputs from the layer, stored as 1. This layer has a single output only.

Data Types: double

OutputNames — Output names

Read-only: {'out'} (default)

This property is read-only.

Output names, stored as {'out'}. This layer has a single output only.

Data Types: cell

Examples

Create 2-D Crop Layer

Create a 2-D crop layer and connect both of the inputs using a dlnetwork object.

Create a dlnetwork object.

net = dlnetwork;

Specify the layers and add them to the network.

layers = [
     imageInputLayer([32 32 3],'Name','image')
     crop2dLayer('centercrop','Name','crop')];
net = addLayers(net,layers);

Connect the image input layer to the "ref" input of the 2-D crop layer.

net = connectLayers(net,'image','crop/ref')

net = 
  dlnetwork with properties:

         Layers: [2×1 nnet.cnn.layer.Layer]
    Connections: [2×2 table]
     Learnables: [0×3 table]
          State: [0×3 table]
     InputNames: {'image'}
    OutputNames: {'crop'}
    Initialized: 0

  View summary with summary.

Algorithms

Layer Input and Output Formats

Most layers in a layer array or layer graph pass data to subsequent layers as formatted dlarray objects. The format of a dlarray object is a string of characters in which each character describes the corresponding dimension of the data. The format consists of one or more of these characters:

• "S" — Spatial

• "C" — Channel

• "B" — Batch

• "T" — Time

• "U" — Unspecified

For example, you can describe 2-D image data that is represented as a 4-D array, where the first two dimensions correspond to the spatial dimensions of the images, the third dimension corresponds to the channels of the images, and the fourth dimension corresponds to the batch dimension, as having the format "SSCB" (spatial, spatial, channel, batch).

You can interact with these dlarray objects in automatic differentiation workflows, such as those for:

• developing a custom layer

• using a functionLayer object

• using the forward and predict functions with dlnetwork objects

This table shows the supported input formats of Crop2DLayer objects and the corresponding output format. If the software passes the output of the layer to a custom layer that does not inherit from the nnet.layer.Formattable class, or to a FunctionLayer object with the Formattable property set to 0 (false), then the layer receives an unformatted dlarray object with dimensions ordered according to the formats in this table. The formats listed here are only a subset of the formats that the layer supports. The layer might support additional formats, such as formats with additional "S" (spatial) or "U" (unspecified) dimensions.

Input Format	Output Format
"SSCB" (spatial, spatial, channel, batch)	"SSCB" (spatial, spatial, channel, batch)
"SSC" (spatial, spatial, channel)	"SSC" (spatial, spatial, channel)

In dlnetwork objects, Crop2DLayer objects also support these input and output format combinations.

Input Format	Output Format
"SSCBT" (spatial, spatial, channel, batch, time)	"SSCBT" (spatial, spatial, channel, batch, time)
"SSCT" (spatial, spatial, channel, time)	"SSCT" (spatial, spatial, channel, time)

Complex Numbers

Crop2DLayer objects support complex-valued input and outputs. (since R2024a) The layer applies the same underlying operation to complex-valued input as it does to real-valued input and outputs complex-valued data where applicable.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Version History

Introduced in R2017b

R2024a: Support for complex-valued inputs and outputs

Crop2DLayer objects support complex-valued input and outputs. The layer applies the same underlying operation to complex-valued input as it does to real-valued input and outputs complex-valued data where applicable.