# Compositing

Combine two images or apply mask to image

• Library:
• Computer Vision Toolbox / Text & Graphics

## Description

The Compositing block combines two images, overlays one image over another, or highlights selected pixels in an image. When combining two images, the block uses this equation, in which the output image O is a linear combination of the two images ${I}_{1}$ and ${I}_{2}$:

`$O\left(i,j\right)=\left(1-X\right)\ast {I}_{1}\left(i,j\right)+X\ast {I}_{2}\left(i,j\right).$`

The opacity factor X scales each pixel before combining the images, where $0\le X\le 1$.

When overlaying one image over another image, or highlighting selected pixels in an input image, the block uses a binary mask to specify which pixels to overwrite or highlight.

Note

This block supports binary, intensity, and color images.

## Ports

### Input

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Input image one, specified as an M-by-N matrix or M-by-N-by-P array. If the input is a M-by-N-by-P array, P is the number of color channels in the image.

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

Input image two, specified as an M-by-N matrix or M-by-N-by-P array. If the input is a M-by-N-by-P array, P is the number of color channels in the image.

#### Dependencies

To enable this port, set the Operation parameter to `Blend` or `Binary mask`.

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

Binary mask, specified as a scalar or matrix. This mask determines which pixels of Image1 the block overwrites with the pixel values of Image2 or highlights, depending on the value of the Operation parameter.

• `Binary mask` — The block overwrites the pixel values of Image1, indicated by the mask, with the corresponding pixel values of Image2. You can specify Mask as a scalar `0` or `1`, which the block uses for all pixels of Image2, or as binary matrix of same size as Image2.

• `Highlight selected pixels` — The block highlights the pixels of Image1 indicated by the mask.

#### Dependencies

To enable this port:

• If overwriting pixel values in one image with pixel values in another image, set the Operation parameter to ```Binary mask``` and the Mask source parameter to `Input port`.

• If highlighting selected pixels in an image, set the Operation parameter to ```Highlight selected pixels```.

Data Types: `single` | `double` | `Boolean`

Opacity factor, specified as a scalar or matrix. If specified as a scalar, the value is the scale of combination for each pixel of Image2 with each corresponding pixel of Image1. If specified as a matrix, its dimensions must match the dimensions of Image2. Each opacity factor must be in the range [0, 1].

#### Dependencies

To enable this port, set the Operation parameter to `Blend` and the Opacity factor(s) source parameter to `Input port`.

Data Types: `single` | `double`

Location index, specified as a two-element vector. The first element represents the row and the second represents the column position of the upper-left corner of Image2, relative to the upper-left corner of Image1. If the location of the upper-left corner of Image2 is such that any of its pixels would render outside the bounds of Image1, the block clips Image2 at the final row or column or Image1, instead.

Note

When the Image1 input has a fixed-point or boolean data type, the Location input must have a built-in integer data type.

#### Dependencies

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

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

### Output

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Output image, returned as an M-by-N matrix or M-by-N-by-P array. If the output is an M-by-N-by-P array, P is the number of color channels in the image.

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

## Parameters

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### Main

Select the image operation for the block to perform.

• `Blend` — Linearly combines the pixel values of Image1 with the pixel values of Image2, with the specified opacity factor.

• `Binary mask` — Overwrites the pixel values of Image1 with the values of Image2 specified by the binary mask.

• `Highlight selected pixels` — Highlights the pixels of Image1 indicated by the binary mask. The highlight operation assign the highest intensity or color values to the pixels of Image1 corresponding to the pixels with logic 1 of the binary mask.

Specify the source of the opacity factor. If you set this parameter to `Input port`, it enables the Factor input port.

#### Dependencies

To enable this parameter, set the Operation parameter to `Blend`.

Defines the scale of combination for each pixel of Image2 with each corresponding pixel of Image1. When you specify the opacity factor as matrix, its dimensions must match the dimensions of Image2. If you specify it as a scalar, the block uses that value as the opacity factor for all pixels of Image2. The opacity factor must be in the range [0, 1].

#### Dependencies

To enable this parameter, set the Operation parameter to `Blend` and the Opacity factor(s) source parameter to ```Specify via dialog```.

Select the source of the overlay location. If you set this parameter to `Input port`, it enables the Location input port.

Specify the row and column position of the upper-left corner of Image2, relative to the upper-left corner of Image1, as a two-element vector. If the location of the upper-left corner of Image2 is such that any of its pixels would render outside the bounds of Image1, the block clips Image2 at the final row or column or Image1, instead.

#### Dependencies

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

Select the source of the binary mask. If you set this parameter to `Input port`, it enables the Mask input port.

#### Dependencies

To enable this parameter, set the Operation parameter to `Binary mask`.

Binary mask, specified as a scalar or matrix, defines which pixels of Image1 the block overwrites with the corresponding pixel values of Image2 or highlights. You specify `0` or `1`, which the block uses for all pixels in Image2, or a binary matrix of the same size of as Image2.

#### Dependencies

To enable this parameter, set the Operation parameter to `Binary mask` and the Mask source parameter to `Specify via dialog`.

### Data Types

For details on the fixed-point block parameters, see Specify Fixed-Point Attributes for Blocks.

## Block Characteristics

 Data Types `Boolean` | `double` | `fixed point` | `integer` | `single` Multidimensional Signals `yes` Variable-Size Signals `yes`

## Version History

Introduced before R2006a