Image class

Applies to Windows and Windows Phone

Represents a control that displays an image. The image source is specified by referring to an image file, using several supported formats. The image source can also be set with a stream. See Remarks for the list of supported image source formats.

Inheritance

Object
  DependencyObject
    UIElement
      FrameworkElement
        Image

Syntax


public ref class Image sealed : FrameworkElement

Attributes

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]
[WebHostHidden()]

Members

The Image class has these types of members:

Constructors

The Image class has these constructors.

ConstructorDescription
Image Initializes a new instance of the Image class.

 

Events

The Image class has these events.

EventDescription
DataContextChanged Occurs when the value of the FrameworkElement.DataContext property changes. (Inherited from FrameworkElement)
DoubleTapped Occurs when an otherwise unhandled DoubleTap interaction occurs over the hit test area of this element. (Inherited from UIElement)
DragEnter Occurs when the input system reports an underlying drag event with this element as the target. (Inherited from UIElement)
DragLeave Occurs when the input system reports an underlying drag event with this element as the origin. (Inherited from UIElement)
DragOver Occurs when the input system reports an underlying drag event with this element as the potential drop target. (Inherited from UIElement)
Drop Occurs when the input system reports an underlying drop event with this element as the drop target. (Inherited from UIElement)
GotFocus Occurs when a UIElement receives focus. (Inherited from UIElement)
Holding Occurs when an otherwise unhandled Hold interaction occurs over the hit test area of this element. (Inherited from UIElement)
ImageFailed Occurs when there is an error associated with image retrieval or format.
ImageOpened Occurs when the image source is downloaded and decoded with no failure. You can use this event to determine the natural size of the image source.
KeyDown Occurs when a keyboard key is pressed while the UIElement has focus. (Inherited from UIElement)
KeyUp Occurs when a keyboard key is released while the UIElement has focus. (Inherited from UIElement)
LayoutUpdated Occurs when the layout of the visual tree changes, due to layout-relevant properties changing value or some other action that refreshes the layout. (Inherited from FrameworkElement)
Loaded Occurs when a FrameworkElement has been constructed and added to the object tree, and is ready for interaction. (Inherited from FrameworkElement)
LostFocus Occurs when a UIElement loses focus. (Inherited from UIElement)
ManipulationCompleted Occurs when a manipulation on the UIElement is complete. (Inherited from UIElement)
ManipulationDelta Occurs when the input device changes position during a manipulation. (Inherited from UIElement)
ManipulationInertiaStarting Occurs when the input device loses contact with the UIElement object during a manipulation and inertia begins. (Inherited from UIElement)
ManipulationStarted Occurs when an input device begins a manipulation on the UIElement. (Inherited from UIElement)
ManipulationStarting Occurs when the manipulation processor is first created. (Inherited from UIElement)
PointerCanceled Occurs when a pointer that made contact abnormally loses contact. (Inherited from UIElement)
PointerCaptureLost Occurs when pointer capture previously held by this element moves to another element or elsewhere. (Inherited from UIElement)
PointerEntered Occurs when a pointer enters the hit test area of this element. (Inherited from UIElement)
PointerExited Occurs when a pointer leaves the hit test area of this element. (Inherited from UIElement)
PointerMoved Occurs when a pointer moves while the pointer remains within the hit test area of this element. (Inherited from UIElement)
PointerPressed Occurs when the pointer device initiates a Press action within this element. (Inherited from UIElement)
PointerReleased Occurs when the pointer device that previously initiated a Press action is released, while within this element. (Inherited from UIElement)
PointerWheelChanged Occurs when the delta value of a pointer wheel changes. (Inherited from UIElement)
RightTapped Occurs when a right-tap input stimulus happens while the pointer is over the element. (Inherited from UIElement)
SizeChanged Occurs when either the ActualHeight or the ActualWidth property changes value on a FrameworkElement. (Inherited from FrameworkElement)
Tapped Occurs when an otherwise unhandled Tap interaction occurs over the hit test area of this element. (Inherited from UIElement)
Unloaded Occurs when this object is no longer connected to the main object tree. (Inherited from FrameworkElement)

 

Methods

The Image class has these methods. It also inherits methods from the Object class.

MethodDescription
AddHandler Adds a routed event handler for a specified routed event, adding the handler to the handler collection on the current element. Specify handledEventsToo as true to have the provided handler be invoked even if the event is handled elsewhere. (Inherited from UIElement)
Arrange Positions child objects and determines a size for a UIElement. Parent objects that implement custom layout for their child elements should call this method from their layout override implementations to form a recursive layout update. (Inherited from UIElement)
ArrangeOverride Provides the behavior for the Arrange pass of layout. Classes can override this method to define their own Arrange pass behavior. (Inherited from FrameworkElement)
CancelDirectManipulations Cancels ongoing direct manipulation processing (system-defined panning/zooming) on any ScrollViewer parent that contains the current UIElement. (Inherited from UIElement)
CapturePointer Sets pointer capture to a UIElement. Once captured, only the element that has capture will fire pointer-related events. (Inherited from UIElement)
ClearValue Clears the local value of a dependency property. (Inherited from DependencyObject)
FindName Retrieves an object that has the specified identifier name. (Inherited from FrameworkElement)
FindSubElementsForTouchTargeting Enables a UIElement subclass to expose child elements that assist with resolving touch targeting. (Inherited from UIElement)
GetAnimationBaseValue Returns any base value established for a dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject)
GetBindingExpression Returns the BindingExpression that represents the binding on the specified property. (Inherited from FrameworkElement)
GetValue Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject)
GoToElementStateCore When implemented in a derived class, enables per-state construction of a visual tree for a control template in code, rather than by loading XAML for all states at control startup. (Inherited from FrameworkElement)
InvalidateArrange Invalidates the arrange state (layout) for a UIElement. After the invalidation, the UIElement will have its layout updated, which will occur asynchronously. (Inherited from UIElement)
InvalidateMeasure Invalidates the measurement state (layout) for a UIElement. (Inherited from UIElement)
Measure Updates the DesiredSize of a UIElement. Typically, objects that implement custom layout for their layout children call this method from their own MeasureOverride implementations to form a recursive layout update. (Inherited from UIElement)
MeasureOverride Provides the behavior for the Measure pass of the layout cycle. Classes can override this method to define their own Measure pass behavior. (Inherited from FrameworkElement)
OnApplyTemplate Invoked whenever application code or internal processes (such as a rebuilding layout pass) call ApplyTemplate. In simplest terms, this means the method is called just before a UI element displays in your app. Override this method to influence the default post-template logic of a class. (Inherited from FrameworkElement)
OnCreateAutomationPeer When implemented in a derived class, returns class-specific AutomationPeer implementations for the Microsoft UI Automation infrastructure. (Inherited from UIElement)
OnDisconnectVisualChildren Override this method to implement how layout and logic should behave when items are removed from a class-specific content or children property. (Inherited from UIElement)
ReadLocalValue Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject)
ReleasePointerCapture Releases pointer captures for capture of one specific pointer by this UIElement. (Inherited from UIElement)
ReleasePointerCaptures Releases all pointer captures held by this element. (Inherited from UIElement)
RemoveHandler Removes the specified routed event handler from this UIElement. Typically the handler in question was added by AddHandler. (Inherited from UIElement)
SetBinding Attaches a binding to a FrameworkElement, using the provided binding object. (Inherited from FrameworkElement)
SetValue Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject)
TransformToVisual Returns a transform object that can be used to transform coordinates from the UIElement to the specified object. (Inherited from UIElement)
UpdateLayout Ensures that all positions of child objects of a UIElement are properly updated for layout. (Inherited from UIElement)

 

Properties

The Image class has these properties.

PropertyAccess typeDescription

ActualHeight

Read-onlyGets the rendered height of a FrameworkElement. (Inherited from FrameworkElement)

ActualWidth

Read-onlyGets the rendered width of a FrameworkElement. (Inherited from FrameworkElement)

AllowDrop

Read/writeGets or sets a value that determines whether this UIElement can be a drop target for purposes of drag-and-drop operations. (Inherited from UIElement)

BaseUri

Read-onlyGets a Uniform Resource Identifier (URI) that represents the base Uniform Resource Identifier (URI) for an XAML-constructed object at XAML load time. This property is useful for Uniform Resource Identifier (URI) resolution at run time. (Inherited from FrameworkElement)

CacheMode

Read/writeGets or sets a value that indicates that rendered content should be cached as a composited bitmap when possible. (Inherited from UIElement)

Clip

Read/writeGets or sets the RectangleGeometry used to define the outline of the contents of a UIElement. (Inherited from UIElement)

CompositeMode

Read/writeGets or sets a property that declares alternate composition and blending modes for the element in its parent layout and window. This is relevant for elements that are involved in a mixed XAML / Microsoft DirectX UI. (Inherited from UIElement)

DataContext

Read/writeGets or sets the data context for a FrameworkElement when it participates in data binding. (Inherited from FrameworkElement)

DesiredSize

Read-onlyGets the size that this UIElement computed during the measure pass of the layout process. (Inherited from UIElement)

Dispatcher

Read-onlyGets the CoreDispatcher that this object is associated with. The CoreDispatcher represents a facility that can access the DependencyObject on the UI thread even if the code is initiated by a non-UI thread. (Inherited from DependencyObject)

FlowDirection

Read/writeGets or sets the direction in which text and other UI elements flow within any parent element that controls their layout. This property can be set to either LeftToRight or RightToLeft. Setting FlowDirection to RightToLeft on any element sets the alignment to the right, the reading order to right-to-left and the layout of the control to flow from right to left. (Inherited from FrameworkElement)

Height

Read/writeGets or sets the suggested height of a FrameworkElement. (Inherited from FrameworkElement)

HorizontalAlignment

Read/writeGets or sets the horizontal alignment characteristics that are applied to a FrameworkElement when it is composed in a layout parent, such as a panel or items control. (Inherited from FrameworkElement)

IsDoubleTapEnabled

Read/writeGets or sets a value that determines whether the DoubleTapped event can originate from that element. (Inherited from UIElement)

IsHitTestVisible

Read/writeGets or sets whether the contained area of this UIElement can return true values for hit testing. (Inherited from UIElement)

IsHoldingEnabled

Read/writeGets or sets a value that determines whether the Holding event can originate from that element. (Inherited from UIElement)

IsRightTapEnabled

Read/writeGets or sets a value that determines whether the RightTapped event can originate from that element. (Inherited from UIElement)

IsTapEnabled

Read/writeGets or sets a value that determines whether the Tapped event can originate from that element. (Inherited from UIElement)

Language

Read/writeGets or sets localization/globalization language information that applies to a FrameworkElement, and also to all child elements of the current FrameworkElement in the object representation and in UI. (Inherited from FrameworkElement)

ManipulationMode

Read/writeGets or sets the ManipulationModes value used for UIElement behavior and interaction with gestures. Setting this value enables handling the manipulation events from this element in app code. (Inherited from UIElement)

Margin

Read/writeGets or sets the outer margin of a FrameworkElement. (Inherited from FrameworkElement)

MaxHeight

Read/writeGets or sets the maximum height constraint of a FrameworkElement. (Inherited from FrameworkElement)

MaxWidth

Read/writeGets or sets the maximum width constraint of a FrameworkElement. (Inherited from FrameworkElement)

MinHeight

Read/writeGets or sets the minimum height constraint of a FrameworkElement. (Inherited from FrameworkElement)

MinWidth

Read/writeGets or sets the minimum width constraint of a FrameworkElement. (Inherited from FrameworkElement)

Name

Read/writeGets or sets the identifying name of the object. When a XAML processor creates the object tree from XAML markup, run-time code can refer to the XAML-declared object by this name. (Inherited from FrameworkElement)

NineGrid

Read/writeGets or sets a value for a nine-grid metaphor that controls how the image can be resized. The nine-grid metaphor enables you to stretch edges and corners of an image differently than its center.

NineGridProperty

Read-onlyIdentifies the NineGrid dependency property.

Opacity

Read/writeGets or sets the degree of the object's opacity. (Inherited from UIElement)

Parent

Read-onlyGets the parent object of this FrameworkElement in the object tree. (Inherited from FrameworkElement)

PlayToSource

Read-onlyGets the information that is transmitted if the Image is used for a Play To scenario.

PlayToSourceProperty

Read-onlyIdentifies the PlayToSource dependency property.

PointerCaptures

Read-onlyGets the set of all captured pointers, represented as Pointer values. (Inherited from UIElement)

Projection

Read/writeGets or sets the perspective projection (3-D effect) to apply when rendering this element. (Inherited from UIElement)

RenderSize

Read-onlyGets the final render size of a UIElement. (Inherited from UIElement)

RenderTransform

Read/writeGets or sets transform information that affects the rendering position of a UIElement. (Inherited from UIElement)

RenderTransformOrigin

Read/writeGets or sets the origin point of any possible render transform declared by RenderTransform, relative to the bounds of the UIElement. (Inherited from UIElement)

RequestedTheme

Read/writeGets or sets the UI theme that is used by the UIElement (and its child elements) for resource determination. The UI theme you specify with RequestedTheme can override the app-level RequestedTheme. (Inherited from FrameworkElement)

Resources

Read/writeGets the locally defined resource dictionary. In XAML, you can establish resource items as child object elements of a frameworkElement.Resources property element, through XAML implicit collection syntax. (Inherited from FrameworkElement)

Source

Read/writeGets or sets the source for the image.

SourceProperty

Read-onlyIdentifies the Source dependency property.

Stretch

Read/writeGets or sets a value that describes how an Image should be stretched to fill the destination rectangle.

StretchProperty

Read-onlyIdentifies the Stretch dependency property.

Style

Read/writeGets or sets an instance Style that is applied for this object during layout and rendering. (Inherited from FrameworkElement)

Tag

Read/writeGets or sets an arbitrary object value that can be used to store custom information about this object. (Inherited from FrameworkElement)

Transitions

Read/writeGets or sets the collection of Transition style elements that apply to a UIElement. (Inherited from UIElement)

Triggers

Read-onlyGets the collection of triggers for animations that are defined for a FrameworkElement. Not commonly used. (Inherited from FrameworkElement)

UseLayoutRounding

Read/writeGets or sets a value that determines whether rendering for the object and its visual subtree should use rounding behavior that aligns rendering to whole pixels. (Inherited from UIElement)

VerticalAlignment

Read/writeGets or sets the vertical alignment characteristics that are applied to a FrameworkElement when it is composed in a parent object such as a panel or items control. (Inherited from FrameworkElement)

Visibility

Read/writeGets or sets the visibility of a UIElement. A UIElement that is not visible is not rendered and does not communicate its desired size to layout. (Inherited from UIElement)

Width

Read/writeGets or sets the width of a FrameworkElement. (Inherited from FrameworkElement)

 

Remarks

Image file formats

An Image can display these image file formats:

  • Joint Photographic Experts Group (JPEG)
  • Portable Network Graphics (PNG)
  • bitmap (BMP)
  • Graphics Interchange Format (GIF)
  • Tagged Image File Format (TIFF)
  • JPEG XR
  • icons (ICO)

    Note  Icon files supported on Windows only. Not supported on Windows Phone 8.1

Setting Image.Source

To set the image source file that an Image displays, you set its Source property, either in XAML or in code. Here's a simple example of setting Source in XAML:


<Image Width="200" Source="Images/myimage.png" />

This usage is setting Source by Uniform Resource Identifier (URI), which is a shortcut that's enabled by XAML. Note that the URI here appears to be a relative URI; supporting partial URIs is another XAML shortcut. The root of this URI is the base folder for an app project. This is usually the same location that the XAML file containing the Image tag is loaded from. In this example, the image source file is in an Images subfolder within the app's file structure.

Setting the Source property is inherently an asynchronous action. Because it's a property, there isn't an awaitable syntax, but for most scenarios you don't need to interact with the asynchronous aspects of image loading. The framework will wait for the image source to be returned, and will start a layout cycle when the image source file is available and decoded.

Setting the source to a URI value that can't be resolved to a valid image source file doesn't throw an exception. Instead, it fires an ImageFailed event. You can write an ImageFailed handler and attach it to the Image object, and possibly use the ErrorMessage in event data to determine the nature of the failure. An error in decoding can also fire ImageFailed. If you want to verify that an image source file was loaded correctly, you can handle the ImageOpened event on the Image element.

You typically use image source files that you have included as part of your app download package. For large files, there might be a very small delay while the image source file is decoded, if this is the first time the source is used. For more info on app resources and how to package image source files in an app package, see Defining app resources.

You can also use image source files that aren't part of the app, for example images from external servers. These images are downloaded by an internal HTTP request, and then decoded. If the image source file is a large file, or if there are connection issues, there might be a delay before an external image can be displayed in an Image element.

Setting Image.Source using code

If you create an Image object using code, call the default constructor, then set the Image.Source property. Setting the Image.Source property requires an instance of the BitmapImage class, which you also must construct. If your image source is a file referenced by URI, use the BitmapImage constructor that takes a URI parameter. When you reference local content, you must include the ms-appx: scheme in the absolute URI that you use as the BitmapImage constructor parameter. In code, you don't get the processing shortcuts for combining relative URI parts and the ms-appx: scheme that happens automatically if you specify Source as a XAML attribute. Instead you must explicitly construct an absolute URI with the appropriate scheme. You typically use the ms-appx: scheme for an image file that's packaged as part of your app.

Tip  If you're using C# or Microsoft Visual Basic, you can get the BaseUri property of the Image, and pass that as the baseUri parameter for System.Uri constructors that combine a URI base location and a relative path within that location.

Here's an example of setting Image.Source in C#. In this example, the Image object was created in XAML but doesn't have a source or any other property values; instead these values are provided at run-time when the Image is loaded from XAML.


void Image_Loaded(object sender, RoutedEventArgs e)
{
    Image img = sender as Image; 
    BitmapImage bitmapImage = new BitmapImage();
    img.Width = bitmapImage.DecodePixelWidth = 80; //natural px width of image source
    // don't need to set Height, system maintains aspect ratio, and calculates the other
    // dimension, so long as one dimension measurement is provided
    bitmapImage.UriSource = new Uri(img.BaseUri,"Images/myimage.png");
}

Using a stream source for an Image source

If your image source is a stream, you must write code that sets your Image instance to use the stream. This can't be done in XAML alone. Construct the Image to use, or reference an existing Image instance (which might have been defined in XAML markup, but without a source). Then use the async SetSourceAsync method of BitmapImage to define the image information from a stream, passing the stream to use as the streamSource parameter. Using a stream for an image source is fairly common. For example, if your app enables a user to choose an image file using a FileOpenPicker control, the object you get that represents the file the user chose can be opened as a stream, but doesn't provide a URI reference to the file.

In this example, the code is already awaitable because it's waiting for the user to choose a file and it only runs after that happens. The stream to use comes from StorageFile.OpenAsync after a StorageFile instance is returned from the async picker actions.


FileOpenPicker open = new FileOpenPicker(); 
// Open a stream for the selected file 
StorageFile file = await open.PickSingleFileAsync(); 
// Ensure a file was selected 
if (file != null) 
{ 
    using (IRandomAccessStream fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read)) 
    { 
        // Set the image source to the selected bitmap 
         BitmapImage bitmapImage = new BitmapImage(); 
         bitmapImage.DecodePixelWidth = 600; //match the target Image.Width, not shown
         await bitmapImage.SetSourceAsync(fileStream); 
         Scenario2Image.Source = bitmapImage; 
    } 
}

Tip  If you're using C# or Visual Basic, streams can use the System.IO.Stream type that you may be familiar with from previous Microsoft .NET programming experience. You can call the AsStream extension method as an instance method on any object of type IRandomAccessStream that you've obtained from a Windows Runtime API. The previous example used IRandomAccessStream for parameter passing and didn't need to use AsStream. But if you ever need to manipulate the stream, AsStream is there as a utility to convert to a System.IO.Stream if you need it.

See XAML images sample for more example code.

Image files and performance

Large image files can impact performance because they load into memory. If you are referencing an image file where you know that the source file is a large, high resolution image, but your app is displaying it in a UI region that's smaller than the image's natural size, you should set the DecodePixelWidth property, or DecodePixelHeight. The DecodePixel* properties enable you to pass information directly to the format-specific codec, and the codec can use this information to decode more efficiently and to a smaller memory footprint. Set DecodePixelWidth to the same pixel width of the area that you want your app to actually display. In other words, DecodePixelWidth for the BitmapImage source should be the same value as the Width or ActualWidth of the Image control that displays that source.

You can either set DecodePixelWidth, or set DecodePixelHeight. If you set one of these two properties, the system calculates the matching property to maintain the correct aspect ratio. You can also set both properties, but you typically should use values that maintain that aspect ratio. If you want to change aspect ratios there are better ways to do so, for example using a TranslateTransform as a RenderTransform.

To set DecodePixelWidth (or DecodePixelHeight) in XAML, you must use a slightly more verbose XAML syntax that includes an explicit BitmapImage element as a property element value, like this:


<Image>
  <Image.Source>
    <BitmapImage DecodePixelWidth="200" UriSource="images/myimage.png" />
  </Image.Source>
</Image>


DecodePixelWidth (or DecodePixelHeight) are properties of BitmapImage, so you need an explicit BitmapImage XAML object element in order to set the DecodePixel* properties as attributes in XAML.

If you are creating an Image instance in code, you are probably already creating a BitmapImage instance as a value to provide for the Source property, so just set DecodePixelWidth (or DecodePixelHeight) on the BitmapImage instance before you set the UriSource property. The DecodePixelType property also affects how pixel values are interpreted by the decode operations.

To prevent images from being decoded more than once, assign image source property from URIs rather than using memory streams whenever you can. The XAML framework can associate the same URI in multiple places with one decoded image, but it cannot do the same for multiple memory streams even if they contain the same data.

You can remove image files from the image cache by setting all associated Image.Source values to null.

For more info on the Image class and performance, see Optimize media resources.

Image file encoding and decoding

The underlying codec support for image files is supplied by Windows Imaging Component (WIC) API. For more info on specific image formats as documented for the codecs, see Native WIC Codecs.

The API for Image, BitmapImage and BitmapSource doesn't include any dedicated methods for encoding and decoding of media formats. All of the decoding operations are built-in as actions that happen when the source is set or reset. This makes the classes easier to use for constructing UI, because they have a default set of supported source file formats and decoding behavior. Classes such as BitmapImage expose some of the decoding options and logic as part of event data for ImageOpened or ImageFailed events. If you need advanced image file decoding, or image encoding, you should use the APIs from the Windows.Graphics.Imaging namespace. You might need these APIs if your app scenario involves image file format conversions, or manipulation of an image where the user can save the result as a file. The encoding APIs are also supported by the WIC component of Windows.

Image width and height

The Image class inherits the Width and Height properties from FrameworkElement, and these properties potentially control the size that your Image control will render when it displays in UI. If you don't set a Width or a Height, then the width and height is determined by the natural size of the image source. For example, if you load a bitmap image that is 300 pixels high and 400 pixels wide, as recorded in its source file format, these measurements are used for the width and height when the Image control calculates its natural size. You can check ActualHeight and ActualWidth at run time after the image renders to get the measurement information. Or, you can handle ImageOpened and check image file properties such as PixelHeight and PixelWidth immediately before the image renders.

If you set just one of the Width or Height properties but not both, then the system can use that dimension as guidance and calculate the other one, preserving the aspect ratio. If you're not sure of the source file dimensions, pick the dimension that's the most important to control in your layout scenario and let the system calculate the other dimension, and then the layout behavior of the container will typically adapt the layout to fit.

If you don't set Width and/or Height, and leave the image as its natural size, the Stretch property for the image can control how the image source file will fill the space you specify as Width and Height. The default Stretch value is Uniform, which preserves aspect ratio when it fits the image into a layout container. If the container's dimensions don't have the same aspect ratio, then there will be empty space that's still part of Image but isn't showing any image pixels, at least while using the Uniform value for Stretch. UniformToFill for Stretch won't leave empty space but might clip the image if dimensions are different. Fill for Stretch won't leave empty space, but might change the aspect ratio. You can experiment with these values to see what's best for image display in your layout scenario. Also, be aware that certain layout containers might size an image that has no specific Width and Height to fill the entire layout space, in which case you can choose to set specific sizes on either the image or the container for it.

NineGrid

Using the NineGrid technique is another option for sizing images that have a different natural size than your display area, if the image has regions that should not be scaled uniformly. For example you can use a background image that has an inherent border that should only stretch in one dimension, and corners that shouldn't stretch at all, but the image center can stretch to fit the layout requirements in both dimensions. For more info, see NineGrid.

Resource qualification and localization for Image

Image source files and scaling

You should create your image sources at several recommended sizes, to ensure that your app looks great when Windows 8 scales it. When specifying a Source for an Image, you can use a naming convention for resources that will use the correct resource for device-specific scaling factors. This is determined by the app automatically at run-time. For specifics of the naming conventions to use and more info, see Quickstart: Using file or image resources.

For more info on how to design images properly for scaling, see Guidelines for scaling to pixel density.

Using unqualified resources

Unqualified resources is a technique you can use where the basic resource reference refers to a default resource, and the resource management process can find the equivalent localized resource automatically. You can use automatic handling for accessing unqualified resources with current scale and culture qualifiers, or you can use ResourceManager and ResourceMap with qualifiers for culture and scale to obtain the resources directly. For more info see Resource management system.

FlowDirection for Image

If you set FlowDirection as RightToLeft for an Image, the visual content of an Image is flipped horizontally. However, an Image element does not inherit the FlowDirection value from any parent element. Typically you only want image-flipping behavior in images that are relevant to layout, but not necessarily to elements that have embedded text or other components that wouldn't make sense flipped for a right-to-left audience. To get image-flip behavior, you must set the FlowDirection element on the Image element specifically to RightToLeft, or set the FlowDirection property in code-behind. Consider identifying the Image element by x:Uid, and specifying FlowDirection values as a Windows Runtime resource, so that your localization experts can change this value later without changing the XAML or code.

The Image class and accessibility

The Image class is not a true control class in that it is not a descendant class of Control. You can't call focus to an Image element, or place an Image element in a tab sequence. For more info on the accessibility aspects of using images and the Image element in your UI, see Exposing basic information about UI elements.

Windows 8 behavior

For Windows 8, resources can use a resource qualifier pattern to load different resources depending on device-specific scaling. However, resources aren't automatically reloaded if the scaling factor changes while the app is running. In this case apps would have to take care of reloading resources, by handling the DpiChanged event (or the deprecated LogicalDpiChanged event) and using ResourceManager APIs to manually reload the resource that's appropriate for the new scaling factor. Starting with Windows 8.1, any resource that was originally retrieved for your app is automatically re-evaluated if the scaling factor changes while the app is running. In addition, when that resource is the image source for an Image object, then one of the source-load events (ImageOpened or ImageFailed) is fired as a result of the system's action of requesting the new resource and then applying it to the Image. The scenario where a run-time scale change might happen is if the user moves your app to a different monitor when more than one is available.

If you migrate your app code from Windows 8 to Windows 8.1 you may want to account for this behavior change, because it results in ImageOpened or ImageFailed events that happen at run-time when the scale change is handled, even in cases where the Source is set in XAML. Also, if you did have code that handled DpiChanged/LogicalDpiChanged and reset the resources, you should examine whether that code is still needed given the new Windows 8.1 automatic reload behavior.

Apps that were compiled for Windows 8 but running on Windows 8.1 continue to use the Windows 8 behavior.

Requirements

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8.1 [Windows Runtime apps only]

Namespace

Windows.UI.Xaml.Controls
Windows::UI::Xaml::Controls [C++]

Metadata

Windows.winmd

See also

FrameworkElement
Quickstart: Image and ImageBrush
XAML images sample
Optimize media resources
BitmapSource
FlowDirection
Windows.Graphics.Imaging
Source

 

 

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