Translate

Translate image or video frame

• 

Libraries:
Computer Vision Toolbox / Geometric Transformations

Description

The Translate block shifts an input image or video frame by the number of pixels in the vertical and horizontal directions specified by a two-element offset vector.

Examples

Translate Image in Vertical and Horizontal Directions

Translate an input image in the vertical and horizontal directions.

• Open Model

Ports

Input

Image — Input image or video

matrix | array

Input image or video, specified as an M-by-N matrix, M-by-N-by-T array, M-by-N-by-C array, or M-by-N-by-C-by-T array. T is the number of frames in a video or image sequence, and C is the number of color channels.

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

Offset — Translation value

vector

Translation value, specified as a two-element vector of the form [vertical horizontal]. The vertical value in the vector is the number of pixels to shift the image up or down in the vertical direction. The horizontal element is the number of pixels to shift the image left or right in the horizontal direction. The axes origin is the top-left corner of the input image.

• To translate the image downward, specify positive pixel values to the vertical element.

• To translate the image upward, specify negative pixel values to the vertical element.

• To translate the image to the right, specify positive pixel values to the horizontal element.

• To translate the image to the left, specify negative pixel values to the horizontal element.

Dependencies

To enable this port, set the Offset source parameter to Input port.

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

Output

Output — Translated image or video

matrix | array

Translated image or video, returned as a P-by-Q matrix, P-by-Q-by-T array, P-by-Q-by-C array, or P-by-Q-by-C-by-T array. T is the number of frames in a video or image sequence, and C is the number of color channels.

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

Parameters

Output size after translation — Translated image size

Full (default) | Same as input image

Specify the size of the translated image as Full or Same as input image.

• Full — The block outputs a matrix that contains the entire translated image.

• Same as input image — The block outputs a matrix of the same size as the input image, which contains a portion of the translated image.

Offset source — Source of translation value

Specify via dialog (default) | Input port

Specify the source of translation value as one of these options:

• Specify via dialog — Specify the translation value using the Offset parameter.

• Input port — Specify the translation value using the Offset port.

Offset — Translation value

[1.5 2.3] (default) | two-element vector

Specify the translation value as a two-element vector of the form [vertical horizontal]. The vertical element in the vector is the number of pixels to shift the image up or down in the vertical direction. The horizontal element is the number of pixels to shift the image left or right in the horizontal direction. The axes origin is the top-left corner of the input image.

• To translate the image downward, specify positive pixel values to the vertical element.

• To translate the image upward, specify negative pixel values to the vertical element.

• To translate the image to the right, specify positive pixel values to the horizontal element.

• To translate the image to the left, specify negative pixel values to the horizontal element.

Dependencies

To enable this parameter, set the Offset source parameter to Specify via dialog.

Maximum offset — Translation value limits

[8 10] (default) | two-element vector

Specify the maximum number of pixels to translate the input image in the vertical and horizontal directions, as a vector of the form [vertical horizontal]. The translate block uses this parameter to determine the size of the translated image when the Output size after translation parameter is set to Full and the Offset source parameter is set to Input port. If either input value to the Offset port is greater than the corresponding value of the Maximum offset parameter, the translate block reduces that input translation value to the corresponding maximum translation value.

Dependencies

To enable this parameter, set the Offset source parameter to Input port.

Background fill value — Intensity or color of background in translated image

0 (default) | scalar | RGB triplet

Specify the intensity or color of the background of the translated image as a scalar intensity value or an RGB triplet.

Interpolation method — Method for interpolating translated pixel values

Bilinear (default) | Nearest neighbor | Bicubic

Specify the method by which to interpolate the pixel values of the translated image as one of these options:

• Nearest neighbor —The Translate block uses the value of the nearest pixel for the interpolated pixel.

• Bilinear — The interpolated pixel value is the weighted average of the 4 nearest pixel values.

• Bicubic — The interpolated pixel value is the weighted average of the 16 nearest pixel values.

The number of pixels the block considers for interpolation affects the complexity and accuracy of the computation. The Nearest neighbor interpolation, which uses the fewest pixels, is the most computationally efficient and least accurate, while the Bicubic interpolation is the least computationally efficient and the most accurate. For more information about interpolation methods and kernels, see the More About section and the Create and Compare Resizing Interpolation Kernels example.

Block Characteristics

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

More About

Nearest Neighbor Interpolation

For nearest neighbor interpolation, the block uses nearby, translated, pixel values for the output pixel values.

For example, suppose this matrix, represents your input image,

$$\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\\ 7& 8& 9\end{array}$$

and you want to translate this image 1.7 pixels in the positive horizontal direction using nearest neighbor interpolation. These steps illustrate the nearest neighbor interpolation algorithm followed by the block:

1. Zero pad the input matrix and translate it 1.7 pixels to the right.

   

2. Create the output matrix by replacing each input pixel value with the translated value nearest to it resulting in this matrix:

   $$\begin{array}{ccccc}0& 0& 1& 2& 3\\ 0& 0& 4& 5& 6\\ 0& 0& 7& 8& 9\end{array}$$

Note

Despite specifying a value of 1.7 pixels to translate the image, this method translates the image by 2 pixels. Nearest neighbor interpolation is computationally efficient, but not as accurate as the bilinear and bicubic interpolation methods.

Bilinear Interpolation

For bilinear interpolation, the block uses the weighted average of two translated pixel values for each output pixel value.

For example, suppose this matrix, represents your input image,

$$\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\\ 7& 8& 9\end{array}$$

and you want to translate this image by 0.5 pixels in the positive horizontal direction using bilinear interpolation. These steps illustrate the bilinear interpolation algorithm followed by the block:

1. Zero pad the input matrix and translate it 0.5 pixels to the right.

   

2. Create the output matrix by replacing each input pixel value with the weighted average of the translated pixel values on either side of the input pixel. The result is this matrix which has one column more than the input matrix.

   $$\begin{array}{cccc}0.5& 1.5& 2.5& 1.5\\ 2& 4.5& 5.5& 3\\ 3.5& 7.5& 8.5& 4.5\end{array}$$

Bicubic Interpolation

For bicubic interpolation, the block uses the weighted average of four translated pixel values for each output pixel value.

For example, suppose this matrix, represents your input image,

$$\begin{array}{ccc}1& 2& 3\\ 4& 5& 6\\ 7& 8& 9\end{array}$$

and you want to translate this image by 0.5 pixels in the positive horizontal direction using bicubic interpolation. These steps illustrate the bicubic interpolation algorithm followed by the block:

1. Zero pad the input matrix and translate it by 0.5 pixels to the right.

   

2. Create the output matrix by replacing each input pixel value with the weighted average of the two translated values on either side. The result is this matrix which has one column more than the input matrix:

   $$\begin{array}{cccc}0.375& 1.5& 3& 1.625\\ 1.875& 4.875& 6.375& 3.125\\ 3.375& 8.25& 9.75& 4.625\end{array}$$

Extended Capabilities

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

Version History

Introduced before R2006a