insertText
Insert text in image or video
Syntax
Description
inserts numeric values into the input image.RGB
= insertText(I
,position
,numericValue
)
specifies options using one or more name-value arguments in addition to any
combination of input arguments from previous syntaxes. For example,
RGB
= insertText(___,Name=Value
)FontColor="red"
renders the inserted text or numeric
values in red.
Examples
Insert Text into Image
Read the image into the workspace.
I = imread("board.tif");
Create text string that contain fractions.
text_str = cell(3,1); conf_val = [85.212 98.76 78.342]; for ii = 1:3 text_str{ii} = ['Confidence: ' num2str(conf_val(ii), '%0.2f') '%']; end
Define the positions and colors of the text boxes.
position = [23 373; 35 185; 77 107]; box_color = {"red","green","yellow"};
Insert the text strings with their respective box colors, and specify the font size, opacity, and text color of all strings.
RGB = insertText(I,position,text_str,FontSize=18,TextBoxColor=box_color, ... BoxOpacity=0.4,TextColor="white");
Display the image with annotations.
figure
imshow(RGB)
title("Board")
Insert Numeric Values into Image
Read the image into the workspace.
I = imread("peppers.png");
Define the numeric values and their xy-positions.
position = [1 50; 100 50]; value = [555 pi];
Insert the numeric values using the bottom-left corner of each text box as its anchor point.
RGB = insertText(I,position,value,AnchorPoint="LeftBottom");
Display the image with the numeric values inserted.
figure
imshow(RGB)
title("Numeric Values")
Insert the Unicode U+014C into the image.
OWithMacron = native2unicode([hex2dec("C5") hex2dec("8C")],"UTF-8"); RGB = insertText(RGB,[256 50],OWithMacron,font="LucidaSansRegular",TextBoxColor="white");
Display the image with the Unicode character inserted.
figure
imshow(RGB)
title("Numeric Values");
Input Arguments
I
— Input image
M-by-N-by-3 truecolor image | M-by-N grayscale image
Input image, specified as an M-by-N-by-3 truecolor or an M-by-N grayscale image.
Data Types: single
| double
| int16
| uint8
| uint16
text
— Unicode text character vector
character vector | string scalar | M-element cell array of character vectors | M-element string array
Unicode text, specified as a character vector, string scalar, M-element
cell array of character vectors, or M-element string
array. M is the number of specified text positions in
position
. The function overwrites pixels with the
value of text
. If you specify a single string or
character vector, the function uses it for all positions in the
position
matrix. Most unicode fonts contain ASCII
characters. You can display non-English and English characters, including
English numeric values, with a single font.
Data Types: char
| string
| cell
numericValue
— Numeric value text
numeric scalar | M-element numeric vector
Numeric value text, specified as a numeric scalar or an M-element numeric
vector. M is the number of specified positions in
position
. If you specify a scalar value, the
function uses that value for all specified positions. The function converts
each numeric value to a character vector using the sprintf
format
'%0.5g
'.
Data Types: numeric
position
— Position of inserted text
M-by-2 matrix
Position of the inserted text, specified as M-by-2 matrix.
M is the number of specified text positions, and each
row specifies the xy-coordinates of the
AnchorPoint
of a text box.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Example: insertText(I,position,text,Font="Calibri")
sets the
font face to Calibri
.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: insertText(I,position,text,"Font","Calibri")
sets the
font face to Calibri
.
Font
— Font face of text
"LucidaSansRegular"
(default) | character vector | string scalar
Font face of the text, specified as a character vector or a string scalar. The font face must
be one of the available truetype fonts installed on your system. To get
a list of available fonts on your system, use the listTrueTypeFonts
function from the MATLAB® command prompt.
Data Types: char
| string
FontSize
— Font size
12
(default) | positive integer in range [1, 200]
Font size, specified as a positive integer in the range [1, 200] in pixels.
Data Types: double
| single
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
FontColor
— Font color
"green"
(default) | short color name | color name | vector of color names | three-column matrix of RGB triplets
Font color, specified as a short color name, color name, vector of color names, three-column matrix of RGB triplets.
The supported colors table lists RGB intensities in the range [0, 1],
but you must specify RGB triplets in the range of your selected data
type. For example, if specifying this argument as a matrix of
uint8
values, you must convert each intensity
value to the range [0, 255]. To convert the listed intensity values to a
uint8
data type, use the code
uint8(255*intensity)
, where intensity is an RGB
triplet value listed in the table.
You can specify a different color for each font string or one color
for all strings. To specify one color for all markers, specify
FontColor
as a color name or an
[R
G
B] vector.
Specification | Format | Example |
---|---|---|
Specify one color for all shapes (or markers) | Short color name or color name |
|
RGB triplet |
| |
Specify a color for each shape (or marker) | Vector of color names |
|
Three-column matrix of RGB triplets | [1 0 0 0 1 1 1 0 1 1 1 1] |
This table lists the supported marker colors.
Color Name | Short Name | RGB Triplet | Appearance |
---|---|---|---|
"red" | "r" | [1 0 0] | |
"green" | "g" | [0 1 0] | |
"blue" | "b" | [0 0 1] | |
"cyan" | "c" | [0 1 1] | |
"magenta" | "m" | [1 0 1] | |
"yellow" | "y" | [1 1 0] | |
"black" | "k" | [0 0 0] | |
"white" | "w" | [1 1 1] |
Data Types: logical
| uint8
| uint16
| int16
| double
| single
TextBoxColor
— Text box color
"green"
(default) | short color name | color name | vector of color names | three-column matrix of RGB triplets
Text box color, specified as a short color name, color name, vector of color names, three-column matrix of RGB triplets.
The supported colors table lists RGB intensities in the range [0, 1],
but you must specify RGB triplets in the range of your selected data
type. For example, if specifying this argument as a matrix of
uint8
values, you must convert each intensity
value to the range [0, 255]. To convert the listed intensity values to a
uint8
data type, use the code
uint8(255*intensity)
, where intensity is an RGB
triplet value listed in the table.
You can specify a different color for each font string or one color
for all strings. To specify one color for all strings, specify
FontColor
as a color name or an
[R
G
B] vector.
Data Types: logical
| uint8
| uint16
| int16
| double
| single
BoxOpacity
— Text box opacity
0.6
(default) | scalar in the range of [0
1
]
Text box opacity of the text label box background, specified as a
scalar in the range of [0, 1]
. A value of
0
renders the background of the label text box as
fully transparent, while a value of 1
renders it as
fully opaque.
Data Types: double
| single
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
AnchorPoint
— Text box reference point
"LeftTop"
(default) | "LeftCenter"
| "LeftBottom"
| "CenterTop"
| "Center"
| "CenterBottom"
| "RightTop"
| "RightCenter"
| "RightBottom"
Text box reference point, specified as one of these values:
"LeftTop"
"LeftCenter"
"LeftBottom"
"CenterTop"
"Center"
"CenterBottom"
"RightTop"
"RightCenter"
"RightBottom"
The anchor point defines the relative location on each
text box. You can position the text box specified by the corresponding
row of position
. For example, to place the center
of the text box at the xy-coordinate specified by
position
, set AnchorPoint
to Center
.
Data Types: char
| string
Output Arguments
RGB
— Output image
M-by-N-by-3 truecolor
image
Output image, returned as an M-by-N-by-3 truecolor image with the specified text inserted.
Limitations
If you do not see a character in the output image, then the specified font does not contain the character. Select a different font. To get a list of available fonts on your system, at the MATLAB command prompt, enter
listTrueTypeFonts
.Increasing the font size also increases the preprocessing time and memory usage.
The
insertText
function does not work for certain composite characters. For example, you cannot insert text when the rendering of one glyph corresponding to a character code influences the position, shape, or size of the adjacent glyph.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
Font
andFontSize
must be compile-time constants.Non-ASCII characters are not supported.
Code generation requires a C++ compiler. For a list of supported compilers, see Supported and Compatible Compilers
Version History
Introduced in R2013aR2023b: Specify RGB color in the range [0,1]
Starting in R2023b, you can specify marker color with RGB values in the range [0,1].
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