Quantcast

Documentation Center

  • Trial Software
  • Product Updates

Image Properties

Define image properties

Creating Image Objects

Use image to create image objects.

Modifying Properties

You can set and query graphics object properties in two ways:

  • Customize Objects in Graph is an interactive tool that enables you to see and change object property values.

  • The set and get commands enable you to set and query the values of properties.

To change the default values of properties, see Setting Default Property Values.

See Core Graphics Objects for general information about this type of object.

Image Property Descriptions

This section provides a description of properties. Curly braces { } enclose default values.

AlphaData

m-by-n matrix of double or uint8

Transparency data. A matrix of non-NaN values specifying the transparency of each face or vertex of the object. The AlphaData can be of class double or uint8.

MATLAB® software determines the transparency in one of the following ways:

  • Using the elements of AlphaData as transparency values (AlphaDataMapping set to none)

  • Using the elements of AlphaData as indices into the current alphamap (AlphaDataMapping set to direct)

  • Scaling the elements of AlphaData to range between the minimum and maximum values of the axes ALim property (AlphaDataMapping set to scaled, the default)

AlphaDataMapping

none | direct | {scaled}

Transparency mapping method. Determines how MATLAB interprets indexed alpha data. Values for this property are:

  • none — The transparency values of AlphaData are between 0 and 1 or are clamped to this range.

  • scaled — Transform the AlphaData to span the portion of the alphamap indicated by the axes ALim property, linearly mapping data values to alpha values (the default).

  • direct — Use the AlphaData as indices directly into the alphamap. When not scaled, the data are usually integer values ranging from 1 to length(alphamap). MATLAB maps values less than 1 to the first alpha value in the alphamap, and values greater than length(alphamap) to the last alpha value in the alphamap. Values with a decimal portion are fixed to the nearest, lower integer. If AlphaData is an array of uint8 integers, then the indexing begins at 0 (that is, MATLAB maps a value of 0 to the first alpha value in the alphamap).

Annotation

hg.Annotation object (read-only)

Handle of Annotation object. The Annotation property enables you to specify whether this image object is represented in a figure legend.

Querying the Annotation property returns the handle of an hg.Annotation object. The hg.Annotation object has a property called LegendInformation, which contains an hg.LegendEntry object.

Once you have obtained the hg.LegendEntry object, you can set its IconDisplayStyle property to control whether the image object is displayed in a figure legend:

IconDisplayStyle ValuePurpose
onRepresent this image object in a legend (default)
offDo not include this image object in a legend
childrenSame as on because image objects do not have children

Setting the IconDisplayStyle property

Set the IconDisplayStyle of a graphics object with handle hobj to off:

hAnnotation = get(hobj,'Annotation');
hLegendEntry = get(hAnnotation,'LegendInformation');
set(hLegendEntry,'IconDisplayStyle','off')

Using the IconDisplayStyle property

See Control Legend Content for more information and examples.

BeingDeleted

on | {off} (read-only)

This object is being deleted. Mechanism to determine if objects are in the process of being deleted. MATLAB sets the BeingDeleted property to on when the object's delete function callback is called (see the DeleteFcn property). It remains set to on while the delete function executes, after which the object no longer exists.

For example, an object's delete function calls other functions that act on a number of different objects. If a function does not need to perform an action on an about-be-deleted object, it can check the object's BeingDeleted property before acting.

BusyAction

cancel | {queue}

Callback queuing

Determines how MATLAB handles the execution of interrupting callbacks.

A running callback is the currently executing callback. The interrupting callback is the callback that tries to interrupt the running callback. The BusyAction property of the interrupting callback determines how MATLAB handles its execution. When the BusyAction property is set to:

  • 'queue' — Puts the interrupting callback in a queue to be processed after the running callback finishes execution.

  • 'cancel' — Discards the interrupting callback as MATLAB finishes execution.

For information about how the Interruptible property of the callback controls whether other callbacks can interrupt the running callback, see the Interruptible property description.

ButtonDownFcn

string | function handle

Button press callback function. Executes whenever you press a mouse button while the pointer is over this object, but not over another graphics object.

See the figure's SelectionType property to determine if modifier keys were also pressed.

This property can be

  • A string that is a valid MATLAB expression

  • The name of a MATLAB file

  • A function handle

Set this property to a function handle that references the callback. The expressions execute in the MATLAB workspace.

For information on the syntax of callback functions, see Function Handle Callbacks.

CData

matrix | m-by-n-by-3 array

The image data. A matrix or 3-D array of values specifying the color of each rectangular area defining the image. image(C) assigns the values of C to CData. MATLAB determines the coloring of the image in one of three ways:

  • Using the elements of CData as indices into the current colormap (the default) (CDataMapping set to direct)

  • Scaling the elements of CData to range between the values min(get(gca,'CLim')) and max(get(gca,'CLim')) (CDataMapping set to scaled)

  • Interpreting the elements of CData directly as RGB values (true color specification)

Note that the behavior of NaNs in image CData is not defined. See the image AlphaData property for information on using transparency with images.

A true color specification for CData requires an m-by-n-by-3 array of RGB values. The first page contains the red component, the second page the green component, and the third page the blue component of each element in the image. RGB values range from 0 to 1. The following picture illustrates the relative dimensions of CData for the two color models.

If CData has only one row or column, the height or width respectively is always one data unit and is centered about the first YData or XData element respectively. For example, using a 4-by-1 matrix of random data:

C = rand(4,1);
image(C,'CDataMapping','scaled')
axis image

produces

CDataMapping

scaled | {direct}

Direct or scaled indexed colors. Determines whether MATLAB interprets the values in CData as indices into the figure colormap (the default) or scales the values according to the values of the axes CLim property.

When CDataMapping is direct, the values of CData should be in the following ranges:

  • In the range 1 to length(get(gcf,'Colormap')) for type double or single

  • In the range 0 to length(get(gcf,'Colormap')) (up to the range limits of the type) for types uint8 and uint16.

  • If CData is of type logical, then the values of 0 index the first color of the colormap and values of 1 index the second color.

If you use true color specification for CData, the CDataMapping property has no effect.

Children

handle

The empty matrix; image objects have no children.

Clipping

{on} | off

Clipping mode. By default, MATLAB clips images to the axes rectangle. If you set Clipping to off, the image can be displayed outside the axes rectangle. For example, if you create an image, set hold to on, freeze axis scaling (with axis manual ), and then create a larger image, it extends beyond the axis limits.

CreateFcn

string | function handle

Callback routine executed during object creation. This property defines a callback routine that executes when MATLAB creates an image object. You must define this property as a default value for images or in a call to the image function to create a new image object. For example, the statement:

set(0,'DefaultImageCreateFcn','axis image')

defines a default value on the root level that sets the aspect ratio and the axis limits so the image has square pixels. MATLAB executes this routine after setting all image properties. Setting this property on an existing image object has no effect.

The handle of the object whose CreateFcn is being executed is accessible only through the root CallbackObject property, which you can query using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

DeleteFcn

function handle | cell array containing function handle and additional arguments | string (not recommended)

Callback executed during object deletion. Executes when this object is deleted (for example, this might happen when you issue a delete command on the object, its parent axes, or the figure containing it). MATLAB executes the callback before destroying the object's properties so the callback routine can query these values. The default is an empty array.

The handle of the object whose DeleteFcn is being executed is accessible only through the root CallbackObject property, which can be queried using gcbo.

For information on the syntax of callback functions, see Function Handle Callbacks.

See the BeingDeleted property for related information.

DisplayName

string

String used by legend. The legend function uses the DisplayName property to label the image object in the legend. The default is an empty string.

  • If you specify string arguments with the legend function, MATLAB set DisplayName to the corresponding string and uses that string for the legend.

  • If DisplayName is empty, legend creates a string of the form, ['data' n], where n is the number assigned to the object based on its location in the list of legend entries. However, legend does not set DisplayName to this string.

  • If you edit the string directly in an existing legend, MATLAB set DisplayName to the edited string.

  • If you specify a string for the DisplayName property and create the legend using the figure toolbar, then MATLAB uses the string defined by DisplayName.

  • To add a legend programmatically that uses the DisplayName string, call legend with the toggle or show option.

See Control Legend Content for more information and examples.

EraseMode

{normal} | none | xor | background

Erase mode. Controls the technique MATLAB uses to draw and erase objects. Use alternative erase modes for creating animated sequences, where control of the way individual objects are redrawn is necessary to improve performance and obtain the desired effect.

  • normal — Redraw the affected region of the display, performing the three-dimensional analysis necessary to correctly render all objects. This mode produces the most accurate picture, but is the slowest. The other modes are faster, but do not perform a complete redraw and are therefore less accurate.

  • none — Do not erase the object when it is moved or destroyed. While the object is still visible on the screen after erasing with EraseMode none, you cannot print it because MATLAB stores no information about its former location.

  • xor — Draw and erase the object by performing an exclusive OR (XOR) with the color of the screen beneath it. This mode does not damage the color of the objects beneath it. However, the object's color depends on the color of whatever is beneath it on the display.

  • background — Erase the object by redrawing it in the axes background Color, or the figure background Color if the axes Color property is none. This damages objects that are behind the erased object, but properly colors the erased object.

Set the axes background color with the axes Color property. Set the figure background color with the figure Color property.

Printing with Nonnormal Erase Modes

MATLAB always prints figures as if the EraseMode of all objects is normal. This means graphics objects created with EraseMode set to none, xor, or background can look different on screen than on paper. On screen, MATLAB mathematically combines layers of colors (for example, performing an XOR on a pixel color with that of the pixel behind it) and ignore three-dimensional sorting to obtain greater rendering speed. However, these techniques are not applied to the printed output.

You can use the getframe command or other screen capture applications to create an image of a figure containing nonnormal mode objects.

HandleVisibility

{on} | callback | off

Control access to object's handle. Determines when an object's handle is visible in its parent's list of children. HandleVisibility is useful for preventing command-line users from accidentally accessing objects that you need to protect for some reason.

  • on — Handles are always visible.

  • callback — Handles are visible from within callback routines or functions invoked by callback routines, but not from within functions invoked from the command line. This provides a means to protect GUIs from command-line users, while allowing callback routines to have access to object handles.

  • off — Handles are invisible at all times. Use this option when a callback invokes a function that could damage the GUI (such as evaluating a user-typed string). This option temporarily hides its own handles during the execution of that function.

Functions Affected by Handle Visibility

When a handle is not visible in its parent's list of children, it cannot be returned by functions that obtain handles by searching the object hierarchy or querying handle properties. This includes get, findobj, gca, gcf, gco, newplot, cla, clf, and close.

Properties Affected by Handle Visibility

When a handle's visibility is restricted using callback or off, the object's handle does not appear in its parent's Children property, figures do not appear in the root's CurrentFigure property, objects do not appear in the root's CallbackObject property or in the figure's CurrentObject property, and axes do not appear in their parent's CurrentAxes property.

Overriding Handle Visibility

You can set the root ShowHiddenHandles property to on to make all handles visible regardless of their HandleVisibility settings. This does not affect the values of the HandleVisibility properties. See also findall.

Handle Validity

Hidden handles are still valid. If you know an object's handle, you can set and get its properties and pass it to any function that operates on handles.

    Note   If you change one data source property to a variable that contains data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

HitTest

{on} | off

Selectable by mouse click. Determines whether this object can become the current object (as returned by the gco command and the figure CurrentObject property) as a result of a mouse click on the objects that compose the area graph. If HitTest is off, clicking this object selects the object below it (which is usually the axes containing it).

Interruptible

off | {on}

Callback routine interruption

Controls whether MATLAB can interrupt an object's callback function when subsequent callbacks attempt to interrupt it.

For Graphics objects, the Interruptible property affects only the callbacks for theButtonDownFcn property. A running callback is the currently executing callback. The interrupting callback is the callback that tries to interrupt the running callback. MATLAB handles both the callbacks based on the Interruptible property of the object of the running callback.

When the Interruptible property is set to:

  • 'off', MATLAB finishes execution of the running callback without any interruptions

  • 'on', these conditions apply:

    • If there is a drawnow, figure, getframe, waitfor, or pause command in the running callback, then MATLAB executes the interrupting callbacks which are already in the queue and returns to finish execution of the current callback.

    • If one of the above functions is not in the running callback, then MATLAB finishes execution of the current callback without any interruption.

BusyAction property of the object of interrupting callback determines whether the callback should be ignored or should be put in the queue.

Setting Interruptible property to on (default), allows a callback from other graphics objects to interrupt callback functions originating from this object.

    Note:   MATLAB does not save the state of properties or the display when an interruption occurs. For example, the handle returned by the gca or gcf command may be changed as another callback is executed.

After the function that interrupts a callback completes, the callback resumes execution where it halted when interrupted. For more information, see Control Callback Execution and Interruption.

Parent

handle of parent axes, hggroup, or hgtransform

Parent of object. Handle of the object's parent. The parent is normally the axes, hggroup, or hgtransform object that contains the object.

Selected

on | {off}

Object selection state. When you set this property to on, MATLAB displays selection handles at the corners and midpoints if the SelectionHighlight property is also on (the default). You can, for example, define the ButtonDownFcn callback to set this property to on, thereby indicating that this particular object is selected. This property is also set to on when an object is manually selected in plot edit mode.

SelectionHighlight

{on} | off

Object highlighted when selected.

  • on — MATLAB indicates the selected state by drawing four edge handles and four corner handles.

  • off — MATLAB does not draw the handles except when in plot edit mode and objects are selected manually.

Tag

string

User-specified object label. Provides a means to identify graphics objects with a user-specified label. The default is an empty string.

Use the Tag property and the findobj function to manipulate specific objects within a plotting hierarchy.

For example, create an areaseries object and set the Tag property.

t = area(Y,'Tag','area1')

When you want to access objects of a given type, use findobj to find the object's handle. The following statement changes the FaceColor property of the object whose Tag is area1.

set(findobj('Tag','area1'),'FaceColor','red')
Type

string (read-only)

Type of graphics object. String that identifies the class of the graphics object. Use this property to find all objects of a given type within a plotting hierarchy. For image objects, Type is always 'image'.

UIContextMenu

handle of uicontextmenu object

Associate context menu with object. Handle of a uicontextmenu object created in the object's parent figure. Use the uicontextmenu function to create the context menu. MATLAB displays the context menu whenever you right-click over the object. The default value is an empty array.

UserData

array

User-specified data. Data you want to associate with this object (including cell arrays and structures). The default value is an empty array. MATLAB does not use this data, but you can access it using the set and get commands.

Visible

{on} | off

Visibility of object and its children.

  • on — Object and all children of the object are visible unless the child object's Visible property is off.

  • off — Object not displayed. However, the object still exists and you can set and query its properties.

XData

[1 size(CData,2)] by default

Control placement of image along x-axis. A vector specifying the locations of the centers of the elements CData(1,1) and CData(m,n), where CData has a size of m-by-n. Element CData(1,1) is centered over the coordinate defined by the first elements in XData and YData. Element CData(m,n) is centered over the coordinate defined by the last elements in XData and YData. The centers of the remaining elements of CData are evenly distributed between those two points.

The width of each CData element is determined by the expression:

(XData(2)-XData(1))/(size(CData,2)-1)

You can also specify a single value for XData. In this case, image centers the first element at this coordinate and centers each following element one unit apart.

YData

[1 size(CData,1)] by default

Control placement of image along y-axis. A vector specifying the locations of the centers of the elements CData(1,1) and CData(m,n), where CData has a size of m-by-n. Element CData(1,1) is centered over the coordinate defined by the first elements in XData and YData. Element CData(m,n) is centered over the coordinate defined by the last elements in XData and YData. The centers of the remaining elements of CData are evenly distributed between those two points.

The height of each CData element is determined by the expression:

(YData(2)-YData(1))/(size(CData,1)-1)

You can also specify a single value for YData. In this case, image centers the first element at this coordinate and centers each following element one unit apart.

See Also

Was this topic helpful?