Image Properties

Image appearance and behavior

Image properties control the appearance and behavior of Image objects. By changing property values, you can modify certain aspects of the image.

Starting in R2014b, you can use dot notation to query and set properties.

im = image(rand(20));
C = im.CData;
im.CDataMapping = 'scaled';

If you are using an earlier release, use the get and set functions instead.

Color and Transparency

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Image color data, specified in one of these forms:

  • Vector or matrix — This format defines indexed image data. Each element defines a color for one pixel of the image. The elements map to colors in the colormap. The CDataMapping property controls the mapping method.

  • 3-D array of RGB triplets — This format defines true color image data using RGB triplet values. Each RGB triplet defines a color for one pixel of the image. An RGB triplet is a three-element vector that specifies the intensities of the red, green, and blue components of the color. The first page of the 3-D array contains the red components, the second page contains the green components, and the third page contains the blue components. Since the image uses true colors instead of colormap colors, the CDataMapping property has no effect.

    • If CData is of type double, then an RGB triplet value of [0 0 0] corresponds to black and [1 1 1] corresponds to white.

    • If CData is an integer type, then the image uses the full range of data to determine the color. For example, if CData is of type uint8, then [0 0 0] corresponds to black and [255 255 255] corresponds to white. If CData is of type int8, then [-128 -128 -128] corresponds to black and [127 127 127] corresponds to white.

    • If CData is of type logical, then [0 0 0] corresponds to black and [1 1 1] corresponds to white.

This illustration shows the relative dimensions of CData for the two color models.

The behavior of NaN elements is not defined.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

Color data mapping method, specified as 'direct' or 'scaled'. Use this property to control the mapping of color data values in CData into the colormap. CData must be a vector or a matrix defining indexed colors. This property has no effect if CData is a 3-D array defining true colors.

The methods have these effects:

  • 'direct' — Interpret the values as indices into the current colormap. Values with a decimal portion are fixed to the nearest lower integer.

    • If the values are of type double or single, then values of 1 or less map to the first color in the colormap. Values equal to or greater than the length of the colormap map to the last color in the colormap.

    • If the values are of type uint8, uint16, uint32, uint64 , int8, int16, int32, or int64, then values of 0 or less map to the first color in the colormap. Values equal to or greater than the length of the colormap map to the last color in the colormap (or up to the range limits of the type).

    • If the values are of type logical, then values of 0 map to the first color in the colormap and values of 1 map to the second color in the colormap.

  • 'scaled' — Scale the values to range between the minimum and maximum color limits. The CLim property of the axes contains the color limits.

Transparency data, specified in one of these forms:

  • Scalar — Use a consistent transparency across the entire image.

  • Array the same size as CData — Use a different transparency value for each image element.

The AlphaDataMapping property controls how MATLAB® interprets the alpha data transparency values.

Example: 0.5

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

Interpretation of AlphaData values, specified as one of these values:

  • 'none' — Interpret the values as transparency values. A value of 1 or greater is completely opaque, a value of 0 or less is completely transparent, and a value between 0 and 1 is semitransparent.

  • 'scaled' — Map the values into the figure’s alphamap. The minimum and maximum alpha limits of the axes determine the alpha data values that map to the first and last elements in the alphamap, respectively. For example, if the alpha limits are [3 5], then alpha data values less than or equal to 3 map to the first element in the alphamap. Alpha data values greater than or equal to 5 map to the last element in the alphamap. The ALim property of the axes contains the alpha limits. The Alphamap property of the figure contains the alphamap.

  • 'direct' — Interpret the values as indices into the figure’s alphamap. Values with a decimal portion are fixed to the nearest lower integer:

    • If the values are of type double or single, then values of 1 or less map to the first element in the alphamap. Values equal to or greater than the length of the alphamap map to the last element in the alphamap.

    • If the values are of type integer, then values of 0 or less map to the first element in the alphamap. Values equal to or greater than the length of the alphamap map to the last element in the alphamap (or up to the range limits of the type). The integer types are uint8, uint16, uint32, uint64 , int8, int16, int32, and int64.

    • If the values are of type logical, then values of 0 map to the first element in the alphamap and values of 1 map to the second element in the alphamap.

Interpolation method, specified as 'nearest' or 'bilinear'. MATLAB uses interpolation to display a scaled or rotated version of the image on your screen. The value you choose does not affect the image array. However, MATLAB saves the interpolated visual representation of the image if you save the figure or export the contents of the axes.

Choose an interpolation method based on your image content and the effect you want to achieve:

  • 'nearest' — This method is best when there are a small number of pixel values that represent distinct categories, or when you want to see individual pixels in a highly zoomed-in view. The value of a pixel located at (x, y) is the value of the pixel that is closest to (x, y) in the original image.

  • 'bilinear' — This method is best in almost all other situations. The value of a pixel located at (x, y) is a weighted average of the surrounding pixels in the original image. To minimize display artifacts, additional smoothing is applied when you shrink the image. If your MATLAB session or figure is using the Painters renderer, then there is no additional smoothing when the image shrinks. To determine the renderer, call the rendererinfo function.

Position

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Placement along the x-axis, specified in one of these forms:

  • Two-element vector — Use the first element as the location for the center of CData(1,1) and the second element as the location for the center of CData(m,n), where [m,n] = size(CData). Evenly distribute the centers of the remaining CData elements between those two points.

    The width of each pixel is determined by the expression:

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

    If XData(1) > XData(2), then the image is flipped left-right.

  • Scalar — Center CData(1,1) at this location and each following element one unit apart.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

Placement along y-axis, specified in one of these forms:

  • Two-element vector — Use the first element as the location for the center of CData(1,1) and the second element as the location for the center of CData(m,n), where [m,n] = size(CData). Evenly distribute the centers of the remaining CData elements between those two points.

    The height of each pixel is determined by the expression:

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

    If YData(1) > YData(2), then the image is flipped up-down.

  • Scalar — Center CData(1,1) at this location and each following element one unit apart.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

Interactivity

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State of visibility, specified as one of these values:

  • 'on' — Display the object.

  • 'off' — Hide the object without deleting it. You still can access the properties of an invisible object.

Data tip content, specified as a DataTipTemplate object. You can control the content that appears in a data tip by modifying the properties of the underlying DataTipTemplate object. For a list of properties, see DataTipTemplate Properties.

For an example of modifying data tips, see Create Custom Data Tips.

This property applies only to images with pinned data tips.

Note

The DataTipTemplate object is not returned by findobj or findall, and it is not copied by copyobj.

Context menu, specified as a ContextMenu object. Use this property to display a context menu when you right-click the object. Create the context menu using the uicontextmenu function.

Note

If the PickableParts property is set to 'none' or if the HitTest property is set to 'off', then the context menu does not appear.

Selection state, specified as one of these values:

  • 'on' — Selected. If you click the object when in plot edit mode, then MATLAB sets its Selected property to 'on'. If the SelectionHighlight property also is set to 'on', then MATLAB displays selection handles around the object.

  • 'off' — Not selected.

Display of selection handles when selected, specified as one of these values:

  • 'on' — Display selection handles when the Selected property is set to 'on'.

  • 'off' — Never display selection handles, even when the Selected property is set to 'on'.

Clipping of the object to the axes limits, specified as one of these values:

  • 'on' — Do not display parts of the object that are outside the axes limits.

  • 'off' — Display the entire object, even if parts of it appear outside the axes limits. Parts of the object might appear outside the axes limits if you create a plot, set hold on, freeze the axis scaling, and then create the object so that it is larger than the original plot.

The Clipping property of the axes that contains the object must be set to 'on'. Otherwise, this property has no effect. For more information about the clipping behavior, see the Clipping property of the axes.

Callbacks

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Mouse-click callback, specified as one of these values:

  • Function handle

  • Cell array containing a function handle and additional arguments

  • Character vector that is a valid MATLAB command or function, which is evaluated in the base workspace (not recommended)

Use this property to execute code when you click the object. If you specify this property using a function handle, then MATLAB passes two arguments to the callback function when executing the callback:

  • Clicked object — Access properties of the clicked object from within the callback function.

  • Event data — Empty argument. Replace it with the tilde character (~) in the function definition to indicate that this argument is not used.

For more information on how to use function handles to define callback functions, see Callback Definition.

Note

If the PickableParts property is set to 'none' or if the HitTest property is set to 'off', then this callback does not execute.

Object creation function, specified as one of these values:

  • Function handle.

  • Cell array in which the first element is a function handle. Subsequent elements in the cell array are the arguments to pass to the callback function.

  • Character vector containing a valid MATLAB expression (not recommended). MATLAB evaluates this expression in the base workspace.

For more information about specifying a callback as a function handle, cell array, or character vector, see Callback Definition.

This property specifies a callback function to execute when MATLAB creates the object. MATLAB initializes all property values before executing the CreateFcn callback. If you do not specify the CreateFcn property, then MATLAB executes a default creation function.

Setting the CreateFcn property on an existing component has no effect.

If you specify this property as a function handle or cell array, you can access the object that is being created using the first argument of the callback function. Otherwise, use the gcbo function to access the object.

Object deletion function, specified as one of these values:

  • Function handle.

  • Cell array in which the first element is a function handle. Subsequent elements in the cell array are the arguments to pass to the callback function.

  • Character vector containing a valid MATLAB expression (not recommended). MATLAB evaluates this expression in the base workspace.

For more information about specifying a callback as a function handle, cell array, or character vector, see Callback Definition.

This property specifies a callback function to execute when MATLAB deletes the object. MATLAB executes the DeleteFcn callback before destroying the properties of the object. If you do not specify the DeleteFcn property, then MATLAB executes a default deletion function.

If you specify this property as a function handle or cell array, you can access the object that is being deleted using the first argument of the callback function. Otherwise, use the gcbo function to access the object.

Callback Execution Control

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Callback interruption, specified as 'on' or 'off'. The Interruptible property determines if a running callback can be interrupted.

There are two callback states to consider:

  • The running callback is the currently executing callback.

  • The interrupting callback is a callback that tries to interrupt the running callback.

Whenever MATLAB invokes a callback, that callback attempts to interrupt the running callback (if one exists). The Interruptible property of the object owning the running callback determines if interruption is allowed. The Interruptible property has two possible values:

  • 'on' — Allows other callbacks to interrupt the object's callbacks. The interruption occurs at the next point where MATLAB processes the queue, such as when there is a drawnow, figure, uifigure, getframe, waitfor, or pause command.

    • If the running callback contains one of those commands, then MATLAB stops the execution of the callback at that point and executes the interrupting callback. MATLAB resumes executing the running callback when the interrupting callback completes.

    • If the running callback does not contain one of those commands, then MATLAB finishes executing the callback without interruption.

  • 'off' — Blocks all interruption attempts. The BusyAction property of the object owning the interrupting callback determines if the interrupting callback is discarded or put into a queue.

Note

Callback interruption and execution behave differently in these situations:

  • If the interrupting callback is a DeleteFcn, CloseRequestFcn or SizeChangedFcn callback, then the interruption occurs regardless of the Interruptible property value.

  • If the running callback is currently executing the waitfor function, then the interruption occurs regardless of the Interruptible property value.

  • Timer objects execute according to schedule regardless of the Interruptible property value.

When an interruption occurs, MATLAB does not save the state of properties or the display. For example, the object returned by the gca or gcf command might change when another callback executes.

Callback queuing, specified as 'queue' or 'cancel'. The BusyAction property determines how MATLAB handles the execution of interrupting callbacks. There are two callback states to consider:

  • The running callback is the currently executing callback.

  • The interrupting callback is a callback that tries to interrupt the running callback.

Whenever MATLAB invokes a callback, that callback attempts to interrupt a running callback. The Interruptible property of the object owning the running callback determines if interruption is permitted. If interruption is not permitted, then the BusyAction property of the object owning the interrupting callback determines if it is discarded or put in the queue. These are possible values of the BusyAction property:

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

  • 'cancel' — Does not execute the interrupting callback.

Ability to capture mouse clicks, specified as one of these values:

  • 'visible' — Capture mouse clicks only when visible. The Visible property must be set to 'on'. The HitTest property determines if the Image object responds to the click or if an ancestor does.

  • 'none' — Cannot capture mouse clicks. Clicking the Image object passes the click to the object behind it in the current view of the figure window. The HitTest property of the Image object has no effect.

Response to captured mouse clicks, specified as one of these values:

  • 'on' — Trigger the ButtonDownFcn callback of the Image object. If you have defined the UIContextMenu property, then invoke the context menu.

  • 'off' — Trigger the callbacks for the nearest ancestor of the Image object that has one of these:

    • HitTest property set to 'on'

    • PickableParts property set to a value that enables the ancestor to capture mouse clicks

Note

The PickableParts property determines if the Image object can capture mouse clicks. If it cannot, then the HitTest property has no effect.

This property is read-only.

Deletion status, returned as 'off' or 'on'. MATLAB sets the BeingDeleted property to 'on' when the DeleteFcn callback begins execution. The BeingDeleted property remains set to 'on' until the component object no longer exists.

Check the value of the BeingDeleted property to verify that the object is not about to be deleted before querying or modifying it.

Parent/Child

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Parent, specified as an Axes, Group, or Transform object.

Children, returned as an empty GraphicsPlaceholder array or a DataTip object array. Use this property to view a list of data tips that are plotted on the chart.

You cannot add or remove children using the Children property. To add a child to this list, set the Parent property of the DataTip object to the chart object.

Visibility of the object handle in the Children property of the parent, specified as one of these values:

  • 'on' — Object handle is always visible.

  • 'off' — Object handle is invisible at all times. This option is useful for preventing unintended changes by another function. Set the HandleVisibility to 'off' to temporarily hide the handle during the execution of that function.

  • 'callback' — Object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line. This option blocks access to the object at the command line, but permits callback functions to access it.

If the object is not listed in the Children property of the parent, then functions that obtain object handles by searching the object hierarchy or querying handle properties cannot return it. Examples of such functions include the get, findobj, gca, gcf, gco, newplot, cla, clf, and close functions.

Hidden object handles are still valid. Set the root ShowHiddenHandles property to 'on' to list all object handles regardless of their HandleVisibility property setting.

Identifiers

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This property is read-only.

Type of graphics object, returned as 'image'.

Object identifier, specified as a character vector or string scalar. You can specify a unique Tag value to serve as an identifier for an object. When you need access to the object elsewhere in your code, you can use the findobj function to search for the object based on the Tag value.

User data, specified as any MATLAB array. For example, you can specify a scalar, vector, matrix, cell array, character array, table, or structure. Use this property to store arbitrary data on an object.

If you are working in App Designer, create public or private properties in the app to share data instead of using the UserData property. For more information, see Share Data Within App Designer Apps.

Introduced before R2006a