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Insert Text

Draw text on images or video frames

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  • Insert Text block

Libraries:
Computer Vision Toolbox / Text & Graphics

Description

The Insert Text block draws formatted text on an input image or video stream. The block produces stylized text bitmaps using the open-source font engine Free Type 2.3.5 library. For more information about the library, see The FreeType Project website.

Note

This block supports only ASCII characters.

This block enables you to insert:

  • A single instance of text

  • Multiple instances of the same text

  • Multiple instances of text, with different text at each location

Examples

Insert Text into Image

Insert Text into Image

Insert colored text into an input image.

Select String to Insert into Image

Select String to Insert into Image

Select a text string and insert it into an image when the Insert Text block contains multiple text strings.

Insert Two Strings into Image at Different Locations

Insert Two Strings into Image at Different Locations

Insert two strings of different colors into an image at different location within the image.

Ports

Input

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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.

Dependencies

To enable this port, set the Image signal parameter to One multidimensional signal.

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

Red color component of the input image or video, specified as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the input video.

Note

Inputs to the R, G, and B ports must have the same dimensions and data type.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Green color component of the input image or video, specified as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the input video.

Note

Inputs to the R, G, and B ports must have the same dimensions and data type.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Blue color component of the input image or video, specified as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the input video.

Note

Inputs to the R, G, and B ports must have the same dimensions and data type.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Select the display text, specified as a positive integer.

Select a display text from the cell array using this port, when the input to the Text parameter is a cell array of character vectors. For example, the value to the Select port must be in the range [1, S], when the Text parameter is a cell array of S character vectors.

Dependencies

To enable this port, specify the Text parameter as a cell array of character vectors.

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

Text color value, specified as a scalar, a vector or a matrix. Use this table to determine the type of input value to this port.

Input ImageSame Color for All TextDifferent Color for Each Character Vector
Intensity imagescalar valueS-element vector. S is the number of character vectors in the cell array specified to Text parameter.
Color imagethree-element vector S-by-3 matrix. S is the number of character vectors in the cell array specified to Text parameter.

The data type of the input image determines the range of color values. For example, a color value for a floating-point input image data type is in the range [0, 1]. For an input image with a uint8 data type, the value is in the range [0, 255].

Note

The input to this port must be of the same data type as the input image.

Dependencies

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

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

Location index, specified as a two-element vector of the form [x y] or an S-by-2 matrix. [x y] specify the coordinates of the input image to display the text. Specify it as an S-by-2 matrix, to display S character vectors at different locations in the image.

Dependencies

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

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

Opacity factor, specified as a scalar or an S-element vector.

  • Scalar — Specify same opacity value to all the display text.

  • S-element vector — Specify different opacity values to S character vectors specified in the Text parameter.

Specify opacity values in the range [0, 1].

Note

The input to the Image, R, G, B, and Color ports must be of the same data type as the input to this port.

Dependencies

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

Data Types: single | double

Text variable values, specified as a scalar or a vector. The block replaces the format specifiers such as %d, %f, or %s in the Text parameter, with the elements specified by the Variables port.

Use the Variables port to display S character vectors or numerical values simultaneously, at S locations of the input image or video frame. The input to this port depends on the type of format specifier specified to the Text parameter.

Display TextData TypeFormat SpecifierInput to the Variables Port
Character vectorsuint8'%s', '%c' ['Text1' 0 'Text2' 0 .... 0 'TextS']
Integersuint8, uint16, uint32, int8, int16, int32'%d', '%i', '%o', '%x', '%X'[x1 x2 x3.... xS]
Floating point numberssingle, double'%f', '%e', '%E', '%g', '%G'[x1 x2 x3.... xS]

For more information on format specifiers, see sprintf.

Dependencies

To enable this port, enter ANSI C printf-style format specifiers, such as '%d', '%f', or '%s' in the Text parameter.

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

Output

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Output image or video, returned 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.

Dependencies

To enable this port, set the Image signal parameter to One multidimensional signal.

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

Red color component of the output image or video, returned as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the output video.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Green color component of the output image or video, returned as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the output video.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Blue color component of the output image or video, returned as an M-by-N matrix or M-by-N-by-T array, where T is the number of frames in the output video.

Dependencies

To enable this port, set the Image signal parameter to Separate color signals.

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

Parameters

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Main

Specify the text to insert into the image, as a character vector or a cell array of character vectors. You can display either a single text or multiple texts simultaneously, using the Text parameter.

  • Single text — You can specify Text parameter as either a character vector or a cell array of S character vectors. If you specify a cell array, select one-out-of-S character vectors from the cell array, by using the Select input port.

  • Multiple texts simultaneously — You can specify ANSI C printf-style format specifiers in the Text parameter. You can then specify the texts by using the Variable input port. Supported format specifiers include %d, %i, %u, %o, %x, %X, %c, %s, %f, %e, %E, %g, and %G. For more information on format specifiers, see sprintf.

Use this table to determine the type of input value to the Text parameter.

DisplayInput toText parameterStatus of Select portStatus of Variables port
A character vectorSingle character vector such as 'Text'DisabledDisabled
One-out-of-S character vectorsCell array of S character vectors such as {'Text1', 'Text2',...., 'TextS'}EnabledDisabled
S character vectors Format specifier such as '%s'DisabledEnabled

Select the text color source as either Specify via dialog or Input port. You can specify this parameter as Specify via dialog to specify insert text colors using the Color value parameter. You can specify this parameter as Input port to specify text colors by using the Color input port.

Text color value specified as a scalar, a vector, or a matrix. Use this table to determine the type of input value to this port.

Input ImageSame Color for All TextDifferent Color for Each Character Vector
Intensity imagescalar valueS-element vector. S is the number of character vectors in the cell array specified to the Text parameter.
Color imagethree-element vector S-by-3 matrix. S is the number of character vectors in the cell array specified to the Text parameter.

The data type of the input image determines the range of color values. For example, a color value for a floating-point input image data type is in the range [0, 1]. For an input image with a uint8 data type, the value is in the range [0, 255].

Dependencies

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

Specify the source of location coordinates of the display text as one these options:

  • Specify via dialog — Use the Location [x y] parameter to specify location coordinates of the display text.

  • Input port — Use the Location input port to specify location coordinates of the display text.

Text location index, specified as a two-element vector [x y] or an S-by-2 matrix. [x y] specify the coordinates of the input image to display the text. Specify the value as an S-by-2 matrix, to display S character vectors at different locations in the image.

Dependencies

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

Specify opacity factor source as one of these options:

  • Specify via dialog — Use the Opacity parameter to specify opacity factor.

  • Input port — Use the Opacity input port to specify opacity factor.

Opacity factor, specified as a scalar or an S-element vector.

  • Scalar — Specify same opacity value to the display text.

  • S-element vector — Specify different opacity values to S character vectors specified to the Text parameter

Specify opacity value in the range [0, 1].

Dependencies

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

Specify the format of the input and output images of the block using these options:

  • One multidimensional signal — The block enables a single input port and single output port.

  • Separate color signals — The block enables R, G, and B input and output signal ports for the respective color channels of the image.

Enable this parameter to mirror the text string and reverse its location in the image from [x y] to [y x].

Font

Specify the font of the inserted text. The block populates this list with the fonts installed on your system. On Windows®, the block searches the system registry for font files. On UNIX, the block searches the font path of the X Server for font files.

Specify the font size of the inserted text.

Enable this parameter to smooth the edges of the inserted text. The smoothing process is computationally expensive.

Block Characteristics

Data Types

Boolean | double | fixed pointa | integer | single

Multidimensional Signals

yes

Variable-Size Signals

yes

a Supports word lengths less than or equal to 32 bits.

Extended Capabilities

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

Version History

Introduced in R2013a

See Also

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