Image Pad

Pad image by adding rows, columns, or both

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Libraries:
Computer Vision Toolbox / Utilities

Description

The Image Pad block expands the dimensions of an image by padding its rows, columns, or both.

Examples

Pad Zeros to Image

Add rows and columns of zeros to an image by using a padding operation.

• Open Model

Ports

Input

I — Input image

matrix | array

Input image, specified as an M-by-N matrix or an M-by-N-by-P array, where P is the number of color planes in the input image.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point

PVal — Pad value

scalar

Pad value, specified as a scalar. The block uses this value for each element of the rows or columns added to the input image.

Dependencies

To enable this port, set the Method parameter to Constant and the Pad value source parameter to Input port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Output

Port_1 — Output image

matrix | array

Output image, returned as a padded matrix or an array. The dimensions of the output image are specified by the Specify parameter.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point

Parameters

Method — Padding method

Constant (default) | Replicate | Symmetric | Circular

Pad the image using one of these methods:

• Constant — Pad the image with a constant value. See Pad with Constant Value.

• Replicate — Pad the image by repeating the border values of the input image. See Pad by Repeating Border Values.

• Symmetric — Pad the image using a mirror image of the input data. See Pad with Mirror Image.

• Circular — Pad the image using a circular repetition of the elements in the input image. See Pad Using Circular Repetition of Elements.

Pad value source — Source of constant pad value

Specify via dialog (default) | Input port

Specify the padding source as Specify via dialog or Input port.

• Specify via dialog — Specify a pad value using the Pad Value parameter.

• Input port — Specify a pad value using the PVal input port.

Dependencies

To enable this parameter, set the Method parameter to Constant.

Pad value — Pad value

0 (default) | scalar

Specify a scalar value with which to pad the image.

Dependencies

To enable this parameter, set the Method parameter to Constant and the Pad value source parameter to Specify via dialog.

Specify — Padding size specification format

Pad size (default) | Output size

Select how to specify the size of the image padding from these two options:

• Pad size — Specify the number of columns and rows with which to pad the image, using the Number of added columns and Number of added rows parameters, respectively.

• Output size — Specify the size of the padded output image using a combination of the Output row mode, Number of output rows, Output column mode, and Number of output columns parameters.

Add columns to — Column padding location

Left (default) | Right | Both left and right | No padding

Select which sides of the input image to pad with additional columns:

• Left — Add columns to the left side of the input image.

• Right — Add columns to the right side of the input image.

• Both left and right — Add columns to both the left and right sides of the input image.

• No padding — Do not add columns to the input image.

Output column mode — Output column sizing method

User-specified (default) | Next power of two

Specify the number of columns in the output image using one of these options:

• User-specified — Specify the number of columns in the output image using the Number of output columns parameter.

• Next power of two — Add columns to the input image until the total number of columns is a power of two.

Dependencies

To enable this parameter, set the Specify parameter to Output size.

Number of output columns — Number of columns in output image

10 (default) | positive integer

Specify the number of columns in the output image as a positive integer M. If the value of this parameter is less than the number of columns in the input image, then the output image contains only the last M columns of the input image.

Dependencies

To enable this parameter, set the Specify parameter to Output size and the Output column mode parameter to User-specified.

Number of added columns — Number of columns added to input image

2 (default) | positive integer | two-element vector of positive integers

Specify how many columns to add to the input signal. The behavior of this parameter changes depending on whether you are padding only one side or both sides of the image.

Add columns to	Number of added columns	Description
Left	P	Add P columns to the left side of the input image.
Right	Q	Add Q columns to the right side of the input image.
Both left and right	[P Q]	Add P columns to the left side and Q columns to the right side of the input image.

Dependencies

To enable this parameter, set the Specify parameter to Pad size and the Add columns to parameter to Left, Right, or Both left and right.

Add rows to — Row padding location

Top (default) | Bottom | Both top and bottom | No padding

Select which sides of the input image to pad with additional rows:

• Top — Add rows to the top of the input image.

• Bottom — Add rows to the bottom of the input image.

• Both top and bottom — Add rows to both the top and bottom of the input image.

• No padding — Do not add rows to the input image.

Output row mode — Output row sizing method

User-specified (default) | Next power of two

Specify the number of rows in the output image using one of these options:

• User-specified — Specify the number of rows in the output image using the Number of output rows parameter.

• Next power of two — Add rows to the input image until the total number of rows is a power of two.

Dependencies

To enable this parameter, set the Specify parameter to Output size.

Number of output rows — Number of rows in output image

12 (default) | positive integer

Specify the number of rows in the output image as a positive integer N. If the value of this parameter is less than the number of rows in the input image, then the output image contains only the last N rows of the input image.

Dependencies

To enable this parameter, set the Specify parameter to Output size and the Output row mode parameter to User-specified.

Number of added rows — Number of rows added to input image

[2 3] (default) | positive integer | two-element vector of positive integers

Specify how many rows to add to the input signal. The behavior of this parameter changes depending on whether you are padding only one side or both sides of the image.

Add rows to	Number of added rows	Description
Top	R	Add R rows to the top of the input image.
Bottom	S	Add S rows to the bottom of the input image.
Both top and bottom	[R S]	Add R rows to the top and S rows to the bottom of the input image.

Dependencies

To enable this parameter, set the Specify parameter to Pad size and the Add rows to parameter to Top, Bottom, or Both top and bottom.

Action when truncation occurs — Action when input signal is truncated

None (default) | Warning | Error

You can specify how the block behaves when the input signal is truncated as one of these options:

• None — Does not notify you when the signal is truncated.

• Warning — Displays a warning message in the MATLAB^® command window when the input signal is truncated.

• Error — Displays an error dialog box and terminates the simulation when the input signal is truncated.

Dependencies

To enable this parameter, set the Specify parameter to Output size.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Multidimensional Signals	no
Variable-Size Signals	no

More About

Pad with Constant Value

When padding an image with a constant value, every element of the rows and columns the Image Pad block adds to the input image is a specified scalar value.

If you want to pad each of your input signal with three initial values equal to 0, and this is how your input signal is defined:

Specify these parameters for the Image Pad block:

• Method — Constant

• Pad value source — Specify via dialog

• Pad value — 0

• Specify — Output size

• Add columns to — Left

• Output column mode — User-specified

• Number of output columns — 6

• Add rows to — No padding

The Image Pad block outputs this signal:

Pad by Repeating Border Values

When padding an image with the Method parameter set to Replicate, the Image Pad block replicates border values of the input signal across all directions.

If you want to pad your input signal with its border values and this is how your input signal is defined:

Specify these parameters for the Image Pad block:

• Method — Replicate

• Specify — Pad size

• Add columns to — Both left and right

• Number of added columns — 2

• Add rows to — Both top and bottom

• Number of added rows = [1 3]

The Image Pad block outputs this signal:

The border values of the input signal are replicated on the top, bottom, left, and right of the input signal, so that the output is a 7-by-7 matrix. The values in the corners of this output matrix are determined by replicating the border values of the matrices on the top, bottom, left, and right sides of the original input signal.

Pad with Mirror Image

When padding an image with the Method parameter set to Symmetric, the Image Pad block flips the original input matrix and each matrix it creates, to populate across all directions of the input signal.

If you want to pad your input signal using its mirror image and this is how your input signal is defined:

Specify these parameters for the Image Pad block:

• Method — Symmetric

• Specify — Pad size

• Add columns to — Both left and right

• Number of added columns — [5 6]

• Add rows to — Both top and bottom

• Number of added rows — 2

The Image Pad block outputs this signal:

The block flips the original input matrix and each matrix it creates about their top, bottom, left, and right sides to populate the 7-by-13 output signal. For example, the block flips the input matrix about its right side to create the matrix directly to its right, but flips that second matrix about its bottom to create the matrix below it.

Pad Using Circular Repetition of Elements

When padding an image with the Method parameter set to Circular, the Image Pad block repeats the values of the input signal in a circular pattern across all directions.

If you want to pad your input signal using a circular repetition of its values and this is how your input signal is defined:

Specify these parameters for the Image Pad block:

• Method — Circular

• Specify — Output size

• Add columns to — Both left and right

• Number of output columns — 9

• Add rows to — Both top and bottom

• Number of output rows — 9

The Image Pad block outputs this signal:

The block repeats the values of the input signal in a circular pattern to populate the 9-by-9 output matrix.

Extended Capabilities

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

Version History

Introduced in R2007a