# Rectangle

Rectangular region of interest

Since R2018b

## Description

A `Rectangle` object specifies the shape and position of a rectangular region-of-interest (ROI). You can customize the appearance and interactive behavior of the ROI.

## Creation

There are two ways to create a `Rectangle` object. For more information, see Create ROI Shapes.

• Use the `drawrectangle` function. Use this function when you want to create the ROI and set the appearance in a single command. You can specify the shape and position of the ROI interactively by drawing the ROI over an image using the mouse, or programmatically by using name-value arguments.

• Use the `images.roi.Rectangle` function described here. Use this function when you want to specify the appearance and behavior of the ROI before you specify the shape and position of the ROI. After creating the object, you can specify the shape and position interactively by using the `draw` function or programmatically by modifying properties of the object.

### Syntax

``roi = images.roi.Rectangle``
``roi = images.roi.Rectangle(ax)``
``roi = images.roi.Rectangle(___,Name,Value)``

### Description

example

````roi = images.roi.Rectangle` creates a `Rectangle` object with default properties.```
````roi = images.roi.Rectangle(ax)` creates an ROI in the axes specified by `ax`.```
````roi = images.roi.Rectangle(___,Name,Value)` sets properties using name-value arguments. You can specify multiple name-value arguments.Example: `images.roi.Rectangle("Color","y")` creates a yellow colored `Rectangle` object.```

### Input Arguments

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Parent of ROI, specified as an `Axes` object or a `UIAxes` object. For information about using an ROI in a UIAxes, including important limitations, see Using ROIs in Apps Created with App Designer.

## Properties

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Aspect ratio of the rectangle, specified as a positive number. The value of this property changes automatically when you draw or resize the rectangle. The `Rectangle` object calculates this value as `height/width`.

ROI color, specified as an RGB triplet, a color name, or a short color name.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color NameShort NameRGB TripletAppearance
`"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]`

Here are the RGB triplets for the default colors that MATLAB® uses in many types of plots.

RGB TripletAppearance
`[0 0.4470 0.7410]`

`[0.8500 0.3250 0.0980]`

`[0.9290 0.6940 0.1250]`

`[0.4940 0.1840 0.5560]`

`[0.4660 0.6740 0.1880]`

`[0.3010 0.7450 0.9330]`

`[0.6350 0.0780 0.1840]`

Example: `"Color","r"`

Example: `"Color","green"`

Example: `"Color",[0 0.4470 0.7410]`

Context menu that displays when you right-click the ROI, specified as a `ContextMenu` object. You can create a custom context menu by using the `uicontextmenu` function and then configuring context menu properties.

Context menu provides an option to delete the ROI, specified as a numeric or logical `1` (`true`) or `0` (`false`). When the value is `true`, you can delete the ROI interactively using the context menu. When the value is `false`, the context menu option to delete the ROI is disabled.

In both cases, you can delete the ROI outside of the context menu by using the `delete` function.

Area of the axes in which you can interactively place the ROI, specified as one of the values in this table.

ValueDescription
`"auto"`The drawing area is the current axes limits (default).
`"unlimited"`The drawing area has no boundary and ROIs can be drawn or dragged to extend beyond the axes limits.
`[x,y,w,h]`The drawing area is restricted to a rectangular region beginning at (x,y), and extending to width w and height h.

Transparency of the ROI face, specified as a number in the range [0, 1]. When the value is `1`, the ROI face is completely opaque. When the value is `0`, the ROI face is completely transparent.

ROI face can capture clicks, specified as a numeric or logical `1` (`true`) or `0` (`false`). When `true`, the ROI face captures mouse clicks. When `false`, the ROI face does not capture mouse clicks.

Aspect ratio remains constant during interaction, specified as a numeric or logical `0` (`false`) or `1` (`true`). When the value is `true`, the aspect ratio remains constant when you draw or resize the ROI. When the value is `false`, you can change the aspect ratio when drawing or resizing the ROI. You can change the state of this property using the default context menu.

Visibility of the ROI handle in the `Children` property of the parent, specified as one of the values in this table.

ValueDescription
`"on"`The object handle is always visible (default).
`"off"`The object handle is hidden at all times.
`"callback"` The object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line.

Interactivity of the ROI, specified as one of the values in this table.

ValueDescription
`"all"`The ROI is fully interactable.
`"none"`The ROI is not interactable, and no drag points are visible.
`"translate"`The ROI can be translated (moved) within the drawing area.

ROI label, specified as a character vector or string scalar. By default, the ROI has no label (`''`).

Transparency of the text background, specified as a number in the range [0, 1]. When set to `1`, the text background is completely opaque. When set to `0`, the text background is completely transparent.

Label text color, specified as an RGB triplet, a color name, or a short color name.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color NameShort NameRGB TripletAppearance
`"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]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB TripletAppearance
`[0 0.4470 0.7410]`

`[0.8500 0.3250 0.0980]`

`[0.9290 0.6940 0.1250]`

`[0.4940 0.1840 0.5560]`

`[0.4660 0.6740 0.1880]`

`[0.3010 0.7450 0.9330]`

`[0.6350 0.0780 0.1840]`

Example: `"LabelTextColor","r"`

Example: `"LabelTextColor","green"`

Example: `"LabelTextColor",[0 0.4470 0.7410]`

Visibility of the ROI label, specified as one of these values:

ValueDescription
`'on'`Label is visible when the ROI is visible and the `Label` property is nonempty (default).
`'hover'`Label is visible only when the mouse hovers over the ROI.
`'inside'`Label is visible only when there is adequate space inside the ROI to display it.
`'off'`Label is not visible.

Width of the ROI border, specified as a positive number in points. The default value is three times the number of points per screen pixel, such that the border is three pixels wide.

Marker size, specified as a positive number in points. The default value is eight times the number of points per screen pixel, such that markers are eight pixels in size.

ROI parent, specified as an `Axes` or `UIAxes` object. For information about using an ROI in a UIAxes, including important limitations, see Using ROIs in Apps Created with App Designer.

Position of the ROI, specified as a 1-by-4 numeric vector of the form `[xmin, ymin, width, height]`. `xmin` and `ymin` specify the location of the upper left corner of the rectangle. `width` and `height` specify the extent to the rectangle in two dimensions.

Rectangle can be rotated, specified as a numeric or logical `0` (`false`) or `1` (`true`). When the value is `false` (default), the rectangle cannot be rotated. When the value is `true`, you can rotate the rectangle by clicking near the markers at the corners.

Angle around the center of the rectangle, specified as a numeric scalar. The angle is measured in degrees in a clockwise direction. The value of this property changes automatically when you draw or move the ROI.

The value of `RotationAngle` does not impact the values in the `Position` property. The `Position` property represents the initial position of the ROI, before rotation. To determine the location of a rotated ROI, use the `Vertices` property.

Selection state of the ROI, specified as a numeric or logical `0` (`false`) or `1` (`true`). You can also set this property interactively. For example, clicking on the ROI selects the ROI and sets this property to `true`. Similarly, pressing the Ctrl key and clicking the ROI deselects the ROI and sets the value of this property to `false`.

Color of the ROI when selected, specified as an RGB triplet, a color name, a short color name, or `"none"`. If you specify `"none"`, then the value of `Color` defines the color of the ROI for all states, selected or not.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color NameShort NameRGB TripletAppearance
`"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]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB TripletAppearance
`[0 0.4470 0.7410]`

`[0.8500 0.3250 0.0980]`

`[0.9290 0.6940 0.1250]`

`[0.4940 0.1840 0.5560]`

`[0.4660 0.6740 0.1880]`

`[0.3010 0.7450 0.9330]`

`[0.6350 0.0780 0.1840]`

Example: `"SelectedColor","r"`

Example: `"SelectedColor","green"`

Example: `"SelectedColor",[0 0.4470 0.7410]`

Color of the ROI stripe, specified as an RGB triplet, a color name, a short color name, or `"none"`. If you specify `"none"`, then the ROI edge is a solid color specified by `Color`. Otherwise, the edge of the ROI is striped, with colors alternating between the colors specified by `Color` and `StripeColor`.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color NameShort NameRGB TripletAppearance
`"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]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB TripletAppearance
`[0 0.4470 0.7410]`

`[0.8500 0.3250 0.0980]`

`[0.9290 0.6940 0.1250]`

`[0.4940 0.1840 0.5560]`

`[0.4660 0.6740 0.1880]`

`[0.3010 0.7450 0.9330]`

`[0.6350 0.0780 0.1840]`

Example: `"StripeColor","r"`

Example: `"StripeColor","green"`

Example: `"StripeColor",[0 0.4470 0.7410]`

Tag to associate with the ROI, specified as a character vector or string scalar. Use the tag value to find the ROI object in a hierarchy of objects using the `findobj` function.

Data to associate with the ROI, specified as any MATLAB data. For example, you can specify a scalar, vector, matrix, cell array, string, character array, table, or structure. The `Rectangle` object does not use this data.

Locations of points on the corners of the ROI, returned as a 4-by-2 numeric matrix.

ROI visibility, specified as `"on"` or `"off"`, or as a numeric or logical `1` (`true`) or `0` (`false`). A value of `"on"` is equivalent to true, and `"off"` is equivalent to false. The value is stored as an on/off logical value of type `OnOffSwitchState`.

ValueDescription
`"on"`Display the ROI.
`"off"`Hide the ROI without deleting it. You still can access the properties of an invisible ROI.

## Object Functions

 `addlistener` Create event listener bound to event source `beginDrawingFromPoint` Begin drawing ROI from specified point `bringToFront` Bring ROI to front of Axes stacking order `createMask` Create binary mask image from ROI `draw` Begin drawing ROI interactively `inROI` Query if points are located in ROI `wait` Block MATLAB command line until ROI operation is finished

## Examples

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Read image into the workspace and display it.

```I = imread('baby.jpg'); figure imshow(I)```

Create a rectangular ROI on the image, using the `Position` parameter to specify its location and size. The example also specifies that the edge of the rectangle is a striped line. For programmatically created ROIs, if you want the ROI drawn in a specific axes, you must specify that axes as an input argument. Otherwise, an instance of the `images.roi.Rectangle` class is created but not displayed. In this example, specify the current axes (`gca`) to draw the ROI on the image in that axes.

`h = images.roi.Rectangle(gca,'Position',[500,500,1000,1000],'StripeColor','r');`

Read an image into the workspace.

`I = imread('cameraman.tif');`

Display the image.

`imshow(I);`

Draw a Rectangle ROI on the image. Because this example specifies the length and location of the ROI, you do not have to call the `draw` method to enable interactive drawing.

`roi = images.roi.Rectangle(gca,'Position',[80,45,80,100]);`

Set up listeners for ROI moving events. When you move it, the ROI sends notifications of these events and executes the callback function you specify.

```addlistener(roi,'MovingROI',@allevents); addlistener(roi,'ROIMoved',@allevents);```

The `allevents` callback function displays at the command line the previous position and the current position of the ROI.

```function allevents(src,evt) evname = evt.EventName; switch(evname) case{'MovingROI'} disp(['ROI moving Previous Position: ' mat2str(evt.PreviousPosition)]); disp(['ROI moving Current Position: ' mat2str(evt.CurrentPosition)]); case{'ROIMoved'} disp(['ROI moved Previous Position: ' mat2str(evt.PreviousPosition)]); disp(['ROI moved Current Position: ' mat2str(evt.CurrentPosition)]); end end```

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## Tips

• To draw the ROI interactively using the `draw` or `drawrectangle` function, position the cursor on the axes and click and drag to create the shape. To finish the ROI, release the mouse button.

• The ROI supports the following interactivity, including keyboard shortcuts.

BehaviorKeyboard shortcut
Cancel drawing the ROI.Press Esc. The function returns a valid ROI object with an empty `Position` property.
Resize (reshape) the ROI.

Position the cursor over a vertex and then click and drag. The rectangle has vertices at each corner and at the midpoint of each side. To preserve the aspect ratio while resizing, press the Shift key. To lock the aspect ratio, use the Fix Aspect Ratio in the right-click context menu.

Move the ROI.Position the cursor over the ROI. The cursor changes to the fleur shape. Click and drag the ROI.
Delete the ROI.Position the pointer on the rectangle, right-click, and choose Delete Rectangle from the context menu. You can also delete the ROI programmatically using the `delete` function.
• For information about using an ROI in an app created with App Designer, see Using ROIs in Apps Created with App Designer.

## Version History

Introduced in R2018b

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